A wound lithium ion battery and an electronic device

Abstract

A wound lithium-ion battery and an electronic device, comprising an electrode assembly, wherein the electrode assembly comprises a first pole piece, a diaphragm and a second pole piece which are stacked and wound in sequence, the first pole piece comprises a first current collector and a plurality of first pole tabs electrically connected to the first current collector, and the second pole piece comprises a second current collector and a plurality of second pole tabs electrically connected to the second current collector; the electrode assembly is flat, and a notch S is provided at at least one corner of the electrode assembly. The multi-pole tab structure is provided to improve the charge and discharge performance of the battery, and at the same time, the battery failure can be avoided when a single pole tab is damaged, thereby improving the safety performance of the battery. The notch is provided to increase the width of the pole piece, reduce the movement space when the battery falls, and improve the energy density of the battery while reducing the risk of battery leakage, thereby improving the safety performance of the battery.

Description

Technical Field

[0001] The embodiments of the present application relate to the technical field of lithium-ion batteries, and in particular to a wound lithium-ion battery and an electronic device. Background Art

[0002] Lithium-ion batteries have been widely used in digital, Bluetooth, wearable and other fields due to their high mass-to-energy ratio, good safety performance, simple preparation, low cost and appearance that can be designed according to customer requirements. In recent years, people have put forward higher and higher requirements on the performance of lithium-ion batteries, so it is urgent to develop lithium-ion batteries with high power, high energy density and high safety performance. Summary of the invention

[0003] The embodiments of the present application aim to provide a wound lithium-ion battery and electrical equipment with high power, high energy density and high safety performance.

[0004] The embodiment of the present application solves its technical problem by adopting the following technical solution: a wound lithium-ion battery is provided, including an electrode assembly, wherein the electrode assembly includes a first pole sheet, a separator and a second pole sheet which are stacked and wound in sequence, the first pole sheet includes a first current collector and a plurality of first pole tabs electrically connected to the first current collector, and the second pole sheet includes a second current collector and a plurality of second pole tabs electrically connected to the second current collector.

[0005] The electrode assembly is flat, and a notch is arranged at at least one corner of the electrode assembly.

[0006] In some embodiments, along the winding direction of the electrode assembly, the edge of the first pole piece is provided with a linear array of first notches, and the edge of the second pole piece is provided with a linear array of second notches corresponding to and matching the first notches. During winding, the corresponding edges of the first notch and the second notch are aligned, and the first notch and the second notch form the notch.

[0007] In some embodiments, along the winding direction of the electrode assembly, the width a of the notch is in the range of 0.2 mm ≤ a ≤ 4 mm.

[0008] In some embodiments, along the extending direction of the first electrode tab, the length b of the notch is in the range of 0.3 mm ≤ b ≤ 4 mm.

[0009] In some embodiments, the width a of the notch is in the range of 0.5 mm ≤ a ≤ 1.5 mm; the length b of the notch is in the range of 0.5 mm ≤ b ≤ 1.5 mm.

[0010] In some embodiments, the area c of the notch is in the range of: 0.05 mm 2 ≤c≤5mm2 .

[0011] In some embodiments, the area c of the notch is in the range of: 0.12 mm 2 ≤c≤1.2mm 2 .

[0012] In some embodiments, the electrode assembly includes an upper end face and a lower end face relative to each other, and a flat portion and a bent portion connected between the upper end face and the lower end face. The first electrode tab extends out of the upper end face. The corner of the electrode assembly is located at the end of the bent portion. The end of the bent portion is where the bent portion extends in a direction perpendicular to the upper end face and / or the lower end face and intersects with the upper end face and / or the lower end face.

[0013] In some embodiments, in the projection of the electrode assembly along its thickness direction, along the extension direction of the electrode lug, the length L1 of the outermost edge of the bent portion and the main body length L2 of the electrode assembly satisfy 0.5mm≤L2-L1≤3mm. The main body length of the electrode assembly is the vertical distance between the upper end face and the lower end face.

[0014] In some embodiments, along the winding direction of the electrode assembly, the difference between the width of the upper end surface and / or the lower end surface and the main body width of the electrode assembly ranges from 0.3 mm to 8 mm. The main body width of the electrode assembly is the distance between the outermost projected edges of the two bent portions.

[0015] In some embodiments, the corner of the electrode assembly includes the intersection of the extension line of the outermost projected edge of the bend portion and the upper end surface and / or the lower end surface.

[0016] In some embodiments, the first pole piece has a first end and a second end opposite to each other, and the first pole piece further comprises a first active material. The first current collector comprises a first side and a first surface and a second surface opposite to each other, the first surface comprises a first coating area and a first uncoated area, the second surface comprises a second coating area, at the first end, the first coating area and the second coating area are flush, and at the second end, the first coating area and the second coating area are misaligned. The first active material is disposed in the first coating area and the second coating area. Each of the first pole tabs protrudes from the first side.

[0017] In some embodiments, the second pole piece has a first end and a second end opposite to each other, and the second pole piece further comprises a second active material. The second current collector comprises a second side and a first surface and a second surface opposite to each other, the first surface of the second current collector comprises a first coating area and a first uncoated area, the second surface of the second current collector comprises a second coating area, at the first end of the second pole piece, the first coating area of ​​the second current collector and the second coating area of ​​the second current collector are flush, and at the second end of the second current collector, the first coating area of ​​the second current collector and the second coating area of ​​the second current collector are misaligned. The second active material is disposed in the first coating area of ​​the second current collector and the second coating area of ​​the second current collector. Each second pole ear protrudes from the second side.

[0018] In some embodiments, along the winding direction of the electrode assembly, at the tail end of the first pole sheet, the first coating area and the second coating area on the first pole sheet are misaligned.

[0019] In some embodiments, along the winding direction of the electrode assembly, at the starting end of the second pole piece, the first coating area and the second coating area on the second pole piece are misaligned.

[0020] In some embodiments, the first end and the second end of the first pole piece both include a current collector without an active material layer on both sides.

[0021] In some embodiments, the first end and the second end of the second pole piece both include a current collector without an active material layer on both sides.

[0022] In some embodiments, along the winding direction of the electrode assembly, when the first coating area and the second coating area on the first pole sheet are misaligned at the tail end of the first pole sheet, and the first coating area and the second coating area on the second pole sheet are misaligned at the starting end of the second pole sheet, the tail end of the first pole sheet includes a current collector without an active material layer on both sides, and the tail end and starting end of the second pole sheet both include a current collector without an active material layer on both sides.

[0023] In some embodiments, the wound lithium-ion battery also includes a shell, the electrode assembly is accommodated in the shell, the shape of the shell is adapted to the shape of the electrode assembly, the shell is provided with rounded corners corresponding to and matching the notch, and the first pole ear and the second pole ear both extend out of the shell.

[0024] In some embodiments, a difference d between a length of the shell and a length of the electrode assembly is in a range of 1.8 mm ≤ d ≤ 3.3 mm.

[0025] In some embodiments, the rounded corner is an outward convex corner, and the notch is an inward concave corner.

[0026] An embodiment of the present application further provides an electronic device, comprising the above-mentioned wound lithium-ion battery.

[0027] Beneficial effects of the embodiments of the present application:

[0028] The embodiments of the present application provide a wound lithium-ion battery and an electronic device. The multi-pole ear structure improves the charge and discharge performance of the battery, and can avoid battery failure when a single pole ear is damaged, thereby improving the safety performance of the battery. However, the multi-pole ear structure has a large head space, and is easy to move in the battery packaging bag, causing the battery to fall and fail, especially at the corner position. By setting a notch at the corner of the electrode assembly, the width of the pole piece can be appropriately increased, and the space for the electrode assembly to move in the packaging bag can be reduced. While improving the energy density of the lithium-ion battery, the possibility of the corner of the electrode assembly breaking the packaging bag can be greatly reduced, thereby improving the harm caused by falling and improving the safety performance of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] One or more embodiments are exemplarily described by pictures in the corresponding drawings, and these exemplified descriptions do not constitute limitations on the embodiments. Elements with the same reference numerals in the drawings represent similar elements, and unless otherwise stated, the figures in the drawings do not constitute proportional limitations.

[0030] Figure 1 A schematic plan view of a wound lithium-ion battery provided in an embodiment of the present application;

[0031] Figure 2 yes Figure 1 A schematic diagram of the structure of an electrode assembly in a wound lithium-ion battery shown;

[0032] Figure 3 It is a schematic diagram of the structure of the pole piece and the diaphragm in the unfolded state;

[0033] Figure 4 yes Figure 3 A schematic diagram of the structure of the first pole piece in one embodiment of the structure shown;

[0034] Figure 5 yes Figure 4 A top view of the first pole piece shown;

[0035] Figure 6 yes Figure 3 A schematic diagram of the structure of the second pole piece in one embodiment of the structure shown;

[0036] Figure 7 yes Figure 6 A top view of the second pole piece shown;

[0037] Figure 8 is a top view of an electrode assembly according to an embodiment of the present application;

[0038] Fig. 9 yes Figure 3 A schematic structural diagram of a first pole piece in an embodiment of the structure shown;

[0039] Fig.10 yes Fig. 9 A top view of the first pole piece shown;

[0040] Fig.11 yes Figure 3 A schematic diagram of the structure of the second pole piece in one embodiment of the structure shown;

[0041] Fig.12 yes Fig.11 A top view of the second pole piece shown;

[0042] Fig.13 is a top view of an electrode assembly according to an embodiment of the present application;

[0043] Fig.14 Figure 3 A schematic diagram of the structure of the first pole piece in one embodiment of the structure shown;

[0044] Fig.15 yes Fig.14 A top view of the first pole piece shown;

[0045] Fig.16 yes Figure 3 A schematic diagram of the structure of the second pole piece in one embodiment of the structure shown;

[0046] Fig.17 yes Fig.16 A top view of the second pole piece shown;

[0047] Fig.18 is a top view of an electrode assembly according to an embodiment of the present application;

[0048] Fig.19 Figure 3 A schematic diagram of the structure of the first pole piece in one embodiment of the structure shown;

[0049] Fig. 20 yes Fig.19 A top view of the first pole piece shown;

[0050] Fig.21 yes Figure 3 A schematic diagram of the structure of the second pole piece in one embodiment of the structure shown;

[0051] Fig. 22 yes Fig.21 A top view of the second pole piece shown;

[0052] Fig.23 It is a top view of the electrode assembly according to an embodiment of the present application. DETAILED DESCRIPTION

[0053] In order to facilitate the understanding of the present application, the present application is described in more detail below in conjunction with the accompanying drawings and specific embodiments. It should be noted that when an element is described as "connected" to another element, it can be directly connected to another element, or there can be one or more centered elements therebetween. The orientation or positional relationship indicated by the terms "starting end", "ending end", "first end", "second end", "head" and the like used in this specification is based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. In addition, the terms "first", "second" and the like are only used for descriptive purposes and cannot be understood as indicating or implying relative importance.

[0054] Unless otherwise defined, all technical and scientific terms used in this specification have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used in this specification includes any and all combinations of one or more of the related listed items.

[0055] In addition, the technical features involved in the different embodiments of the present application described below can be combined with each other as long as they do not conflict with each other.

[0056] See also Figure 1 , is a plan schematic diagram of a wound lithium-ion battery 100 provided in an embodiment of the present application. The wound lithium-ion battery 100 is flat and includes a shell 10 and an electrode assembly 20. The electrode assembly 20 is flat and is accommodated in the shell 10.

[0057] In the related art, the corners of the lithium-ion battery shell are generally punched at right angles. When punching, the corners are easily stretched, causing battery leakage and affecting the safety performance of the battery. Therefore, the four corners of the shell are punched into arc-shaped rounded corners to reduce the risk of leakage caused by punching. This application is no exception. Figure 1 As shown, the shape of the shell 10 is adapted to the shape of the electrode assembly 20 , and rounded corners 11 are provided at the corners of the shell 10 .

[0058] In some embodiments, the housing 10 is also called a packaging bag, and the packaging bag is an aluminum-plastic film.

[0059] Please also read Figure 2 and Figure 3 The electrode assembly 20 includes a first pole piece 21, a diaphragm 22 and a second pole piece 23 which are stacked and wound in sequence. The first pole piece 21 includes a plurality of first pole tabs 212, and the second pole piece 23 includes a plurality of second pole tabs 232. Both the first pole tabs 212 and the second pole tabs 232 extend out of the housing 10. Here, "plurality" means two or more.

[0060] In some embodiments, the first electrode tab 212 and the second electrode tab 232 may be located at the same end of the electrode assembly 20 , or at different ends of the electrode assembly.

[0061] The setting of multiple pole ears can improve the discharge performance of the pole piece, making the lithium-ion battery have high power. However, since the head of the electrode assembly 20 needs to be folded, the shell of the multi-pole ear structure needs to reserve a larger space than the conventional single-pole ear structure, which greatly increases the possibility of the electrode assembly 20 jumping in the shell 10 and increases the probability of the lithium-ion battery falling and failing. When the corner position of the electrode assembly 20 is a right angle, the corner position is most likely to fail.

[0062] In addition, after the corners of the shell 10 are rounded, the size of the right-angled corners of the electrode assembly 20 exceeds the rounded corners, making it impossible for the electrode assembly 20 to be loaded into the aluminum-plastic film. Therefore, it is necessary to reduce the size of the electrode assembly 20, such as reducing the length of the electrode assembly, that is, reducing the width of the electrode sheet, to increase the gap between the electrode assembly 20 and the shell 10, but this method will inevitably reduce the energy density of the lithium-ion battery.

[0063] It should be noted that the gap between the electrode assembly 20 and the shell 10 is the difference between the length of the shell 10 and the length of the electrode assembly 20 .

[0064] See also Figure 2 In some embodiments, in order to improve the safety performance and energy density of the lithium-ion battery, a notch S is provided at at least one corner of the electrode assembly 20 , and the notch S corresponds to and matches the rounded corner 11 on the shell 10 .

[0065] Specifically, the electrode assembly 20 includes an upper end face and a lower end face opposite to each other, and a flat portion 201 and a bent portion 202 connected between the upper end face and the lower end face. The pole ear extends out of the upper end face. The angular position of the electrode assembly 20 is located at the end of the bent portion 202, and the end of the bent portion 202 is the portion where the bent portion 202 extends in a direction perpendicular to the upper end face and / or the lower end face and intersects with the upper end face and / or the lower end face. In the projection of the electrode assembly 20 along its thickness direction, along the extension direction of the pole ear (the length direction of the electrode assembly), the difference between the length L1 of the outermost edge of the bent portion and the length L2 of the electrode assembly body ranges from 0.5 mm to 3 mm; along the winding direction of the electrode assembly, the difference between the width of the upper end face and / or the lower end face and the width of the electrode assembly body ranges from 0.3 mm to 8 mm. The length of the electrode assembly body is the vertical distance between the upper end face and the lower end face; the width of the electrode assembly body is the distance between the outermost projected edges of the two bent portions. The corner of the electrode assembly 20 includes the intersection of the extension line of the outermost projected edge of the bending portion and the upper end surface and / or the lower end surface.

[0066] After the notch S is provided at the corner of the electrode assembly 20, the width of the electrode piece can be appropriately increased, the difference between the length of the shell 10 and the length of the electrode assembly 20 can be reduced, and the space for the electrode assembly 20 to move around in the shell 10 can be reduced. While improving the energy density of the lithium-ion battery, the possibility of the corner of the electrode assembly 20 breaking through the shell 10 can be greatly reduced, thereby improving the hazards caused by falling and improving the safety performance of the lithium-ion battery.

[0067] In some embodiments, Figure 1 As shown, the fillet 11 on the shell 10 is an outer convex corner, and the notch S of the electrode assembly 20 is an inner concave corner.

[0068] In some embodiments, the rounded corner 11 on the shell 10 and the notch S of the electrode assembly 20 are both convex corners or both concave corners.

[0069] It is understood that the number of the gaps S can be 1, 2, 3 or 4, and the present application does not impose any limitation on this. For the convenience of description, the present application embodiment is described by taking the number of the gaps S as 4 as an example.

[0070] In some embodiments, the difference d between the length of the housing 10 and the length of the electrode assembly 20 is in the range of 1.8 mm≤d≤3.3 mm.

[0071] Please also read Figure 2 and Figure 3Along the winding direction of the electrode assembly 20, the edge of the first electrode sheet 21 is provided with a linear array of first notches 211, and the edge of the second electrode sheet 23 is provided with a linear array of second notches 231 corresponding to and matching the first notches 211. During winding, the corresponding edges of the first notch 211 and the second notch 231 are aligned, and the first notch 211 and the second notch 231 form a notch S.

[0072] It can be understood that the above-mentioned notch is half of the first notch or the second notch, and the above-mentioned notch can be triangular, semi-elliptical or semi-circular, etc., and the present application does not impose any restrictions on this. In addition, since the material of the diaphragm 22 is relatively soft and will not cause impact on the housing 10, the diaphragm 22 does not need to be provided with a notch similar to the first pole piece 21 or the second pole piece 23. In the illustrations of the present application, the diaphragm at the notch S has been omitted for ease of understanding.

[0073] The first notch and the second notch may be formed by die cutting or laser cutting when the first pole piece 21 and the second pole piece 23 are formed.

[0074] Preferably, the embodiment of the present application uses laser cutting to form the first notch and / or the second notch. Compared with die cutting, laser cutting is more efficient and stable. For example, the parameters of laser cutting are as follows: the laser cutting speed is 15-30m / min, the cutting frequency is 2000KHZ-4000KHZ, and the cutting power is 130-140W.

[0075] See also Figure 1 In some embodiments, along the winding direction of the electrode assembly 20, the width a of the notch S is in the range of 0.2 mm ≤ a ≤ 4 mm.

[0076] When the width a of the notch S is less than 0.2 mm, the burrs in the cutting process are likely to exceed the standard, and there is a risk of piercing the diaphragm and causing a short circuit in the lithium-ion battery; when the width a of the notch S is greater than 4 mm, the capacity loss of the lithium-ion battery is too large and there is no point in implementing it.

[0077] In some embodiments, the width a of the notch S is in the range of 0.5 mm ≤ a ≤ 1.5 mm.

[0078] In some embodiments, Figure 1 As shown, along the extending direction of the first electrode tab 212 or the second electrode tab 232 , the length b of the notch S is in the range of 0.3 mm ≤ b ≤ 4 mm.

[0079] When the length b of the notch S is in the range of b<0.3mm, the burrs in the cutting process are likely to exceed the standard, and there is a risk of piercing the diaphragm and causing a short circuit in the lithium-ion battery. When the length b of the notch S is in the range of b>4mm, the capacity loss of the lithium-ion battery is too large and there is no point in implementing it.

[0080] In some embodiments, the length b of the notch S is in the range of 0.5 mm ≤ b ≤ 1.5 mm.

[0081] In some embodiments, Figure 1 As shown, the range of the notch area c is: 0.05mm 2 ≤c≤5mm 2 .

[0082] When the area of ​​the notch S is c<0.05mm 2 When the area of ​​the notch S is greater than 5mm, the burrs in the cutting process may exceed the standard, which may pierce the diaphragm and cause the lithium-ion battery to short-circuit. 2 ,The capacity loss of lithium ion batteries is too large and there is no point in implementation.

[0083] In some embodiments, the area c of the notch S is in the range of: 0.12 mm 2 ≤c≤1.2mm 2 The area c of the notch S can be calculated using image processing software. For example, the electrode assembly 20 is placed on a plane, and an image of the electrode assembly is acquired (the lens is facing the flat portion), and the projection of the electrode assembly on the plane is obtained. The projection is a rectangle with a notch. The rectangle is completed using image software and the area of ​​the rectangle is obtained. At the same time, the area of ​​the projection of the electrode assembly is calculated using image recognition technology. The area c of the notch S = (area of ​​the rectangle - area of ​​the projection of the electrode assembly) / number of notches.

[0084] The present application is further described in detail below in conjunction with specific embodiments and drawings of the specification. Of course, the implementation methods of the present application are not limited thereto.

[0085] Example 1

[0086] The four corners of the electrode assembly 20 of the lithium-ion battery are provided with notches S, wherein the width a of the notch is 0.2 mm, the length b of the notch is 0.3 mm, and the area c of the notch is 0.05 mm. 2 The difference d between the length of the shell and the length of the electrode assembly is 3.1 mm. The lithium-ion battery is charged to check whether the lithium-ion battery is leaking, and then the lithium-ion battery is discharged to measure the capacity of the lithium-ion battery.

[0087] Example 2

[0088] The four corners of the electrode assembly 20 in the lithium-ion battery are all provided with notches S, wherein the width a of the notch is 4 mm, the length b of the notch is 4 mm, and the area c of the notch is 5 mm. 2The difference d between the length of the shell and the length of the electrode assembly is 1.8 mm. The lithium-ion battery is charged to check whether the lithium-ion battery is leaking, and then the lithium-ion battery is discharged to measure the capacity of the lithium-ion battery.

[0089] Example 3

[0090] The four corners of the electrode assembly 20 in the lithium-ion battery are all provided with notches S, wherein the length a of the notch is 0.5 mm, the width b of the notch is 0.5 mm, and the area c of the notch is 0.12 mm. 2 The difference d between the length of the shell and the length of the electrode assembly is 2.8 mm. The lithium-ion battery is charged to check whether the lithium-ion battery is leaking, and then the lithium-ion battery is discharged to measure the capacity of the lithium-ion battery.

[0091] Example 4

[0092] The four corners of the electrode assembly 20 of the lithium-ion battery are provided with notches S, wherein the length a of the notch is 1.5 mm, the width b of the notch is 1.5 mm, and the area c of the notch is 1.2 mm. 2 The difference d between the length of the shell and the length of the electrode assembly is 1.8 mm. The lithium-ion battery is charged to check whether the lithium-ion battery is leaking, and then the lithium-ion battery is discharged to measure the capacity of the lithium-ion battery.

[0093] Comparative Example 1

[0094] The electrode assembly 20 of the lithium-ion battery has no notch S, that is, the corner of the electrode assembly 20 is a right angle, and the difference d between the length of the shell and the length of the electrode assembly is 3.3 mm. The lithium-ion battery is charged to check whether it is leaking, and then the lithium-ion battery is discharged to measure the capacity of the lithium-ion battery.

[0095] Comparative Example 2

[0096] The four corners of the electrode assembly 20 in the lithium-ion battery are all provided with notches S, wherein the width a of the notch is 5 mm, the length b of the notch is 5 mm, and the area c of the notch is 12 mm. 2 The difference d between the length of the shell and the length of the electrode assembly is 1.8 mm. The lithium-ion battery is charged to check whether the lithium-ion battery is leaking, and then the lithium-ion battery is discharged to measure the capacity of the lithium-ion battery.

[0097] Performance Testing:

[0098] The lithium ion batteries of Examples 1-4 and Comparative Examples 1 and 2 were tested.

[0099] Specifically, the test conditions are as follows: the length of the electrode assembly 20 in all lithium-ion batteries is 50 mm. The lithium-ion batteries to be tested are placed on the test bench. Each lithium-ion battery is charged, such as fully charged to 4.45V at a constant current of 0.2C, and the lithium-ion battery is observed to see if it leaks. The lithium-ion battery is then discharged at a constant current of 0.2C to a cut-off voltage of 3V, and the capacity of the lithium-ion battery is measured, wherein the capacity of the lithium-ion battery is the product of the time required to discharge the battery at a constant current of 0.2C to a cut-off voltage of 3V and the current. One group is measured 10 times, that is, 10 lithium-ion batteries under the same embodiment or comparative example are tested under the above test conditions. After the test is completed, the capacity of the lithium-ion battery and whether it leaks are checked to determine whether the measures adopted in the present application can improve the energy density of the lithium-ion battery and reduce the risk of battery leakage. The test results are shown in Table 1.

[0100] Table 1 Battery capacity and leakage ratio of the embodiment and the comparative example

[0101]

[0102] It can be seen from Table 1 that providing the notch S at the corner of the electrode assembly 20 can reduce the risk of leakage of the lithium-ion battery.

[0103] According to the comparison between Examples 1-4 and Comparative Example 1, after providing a notch at the corner of the electrode assembly 20, the difference d between the length of the shell and the length of the electrode assembly can be reduced, thereby increasing the capacity of the lithium-ion battery, that is, improving the energy density of the lithium-ion battery.

[0104] According to Example 1-2 and Comparative Example 1-2, although the difference d between the length of the shell and the length of the electrode assembly can be reduced by providing a notch at the corner of the electrode assembly 20, when the width a of the notch is greater than 4 mm, the length b of the notch is greater than 4 mm, and the area c of the notch S is greater than 5 mm, 2 When the capacity of the lithium-ion battery is less than that of the lithium-ion battery without the notch S on the electrode assembly 20, the width of the notch a≤4mm, the length of the notch b≤4mm, and the area of ​​the notch c≤5mm 2 In addition, when the width a of the notch S is less than 0.2 mm, the length b of S is less than 0.3 mm, and the area c of the notch S is less than 0.05 mm 2 When cutting, the burrs in the cutting process are likely to exceed the standard, which may pierce the diaphragm and cause a short circuit in the lithium-ion battery. Therefore, this application is not considered.

[0105] According to the comparison of Examples 1-4, the width of the notch is 0.2 mm ≤ a ≤ 4 mm, the length of the notch is 0.3 mm ≤ b ≤ 4 mm, and the area of ​​the notch is 0.05 mm. 2 ≤c≤5mm 2When the length of the shell and the length of the electrode assembly is reduced from 3.1 mm to 1.8 mm, the capacity of the lithium-ion battery is only 2005 mAh, and the width of the notch S is 0.5 mm ≤ a ≤ 1.5 mm, the length of the notch S is 0.5 mm ≤ b ≤ 1.5 mm, and the area of ​​the notch S is 0.12 mm. 2 ≤c≤1.2mm 2 When the length of the shell and the length of the electrode assembly is d, the difference d between the length of the shell and the length of the electrode assembly can be reduced from 2.8 mm to 1.8 mm, and the capacity range of the lithium-ion battery can be increased from 2012.6 mAh to 2035.1 mAh, both of which are greater than 2005 mAh. Therefore, in a preferred embodiment, the width a of the notch is in the range of 0.5 mm ≤ a ≤ 1.5 mm, the length b of the notch is in the range of 0.5 mm ≤ b ≤ 1.5 mm, and the area c of the notch is in the range of 0.12 mm 2 ≤c≤1.2mm 2 .

[0106] In order to further improve the energy density of lithium-ion batteries, the coating method of the active material layer on the electrode can be changed. Please see below for details.

[0107] Please also read Figure 4 and Figure 6 The first pole piece 21 and the second pole piece 23 both have a first end 24 and a second end 25 opposite to each other. For example, the first pole piece 21 can be formed into a long strip shape, and the first end 24 and the second end 25 can be two ends of the first pole piece 21 in the length direction.

[0108] Please also read Figure 4 and Figure 5 The first pole piece 21 includes a first current collector 200a and a first active material layer 300a. The first current collector 200a includes a first side 210a and a first surface 220a and a second surface 230a opposite to each other. For example, the first surface 220a and the second surface 230a may be two surfaces in the thickness direction of the first current collector 200a, and the first side 210a may be located between the first surface 220a and the second surface 230a.

[0109] The first surface 220a includes a first coating area 221a and a first uncoated area 222a, the second surface 230a includes a second coating area 231a, and the first active material 300a is disposed in the first coating area 221a and the second coating area 231a. It can be understood that the first coating area 221a may be an area on the first surface 220a coated with the first active material 300a, the first uncoated area 222a does not have the first active material 300a, and the second coating area 231a may be an area on the second surface 230a coated with the first active material 300a.

[0110] In some embodiments, the second surface 230a may be completely covered by the first active material 300a. In other words, the second surface 230a is configured to form a second coating area 231a, and the first surface 220a is composed of a first coating area 221a and a first uncoated area 222a.

[0111] like Figure 4 As shown, at the first end 24, the first coating area 221a and the second coating area 231a are flush, and at the second end 25, the first coating area 221a and the second coating area 231a are staggered. It can be understood that the end face of the first coating area 221a close to the first end 24 is flush with the end face of the second coating area 231a close to the first end 24, and the end face of the first coating area 221a close to the second end 25 is staggered with the end face of the second coating area 231a close to the second end 25.

[0112] Each first electrode tab 212 is connected to the first current collector 200a, and each first electrode tab 212 protrudes from the first side edge 210a (eg, Figure 5 shown).

[0113] It should be noted that the connection between the first electrode tab and the first current collector can be understood as signal and energy transmission between the first electrode tab and the first current collector.

[0114] Please also read Figure 6 and Figure 7 The structure of the second pole piece 22 is similar to that of the first pole piece 21. The second pole piece 22 includes a second current collector 200b and a second active material 300b. The second current collector 200b includes a second side 210b and a first surface 220b and a second surface 230b opposite to each other. The first and second side 210b are located between the first surface 220b and the second surface 230b. Each second pole ear 232 is connected to the second current collector 200b, and each second pole ear 232 protrudes from the second side 210b.

[0115] It should be noted that the connection between the second electrode tab and the second current collector can be understood as signal and energy transmission between the second electrode tab and the second current collector.

[0116] The first surface 220b includes a first coating area 221b and a first uncoated area 222b, the second surface 230b includes a second coating area 231b, and the second active material 300b is disposed in the first coating area 221b and the second coating area 231b. It can be understood that the first coating area 221b may be an area on the first surface 220b coated with the second active material 300b, the first uncoated area 222b does not have the second active material 300b, and the second coating area 231b may be an area on the second surface 230b coated with the active material.

[0117] In some embodiments, the second surface 230b may be completely covered by the second active material 300b. In other words, the second surface 230b is configured to form a second coating area 231b, and the first surface 220b is composed of a first coating area 221b and a first uncoated area 222b.

[0118] like Figure 6 As shown, at the first end 24, the first coating area 221b and the second coating area 231b are flush, and at the second end 25, the first coating area 221b and the second coating area 231b are staggered. It can be understood that the end face of the first coating area 221b close to the first end 24 is flush with the end face of the second coating area 231b close to the first end 24, and the end face of the first coating area 221b close to the second end 25 is staggered with the end face of the second coating area 231b close to the second end 25.

[0119] In the related art, the pole piece is usually provided with a pole ear. When the pole ear is damaged or the current collector is broken, the pole piece will fail. In addition, the coating method of the active material on the pole piece is usually non-displacement, that is, the active material on both sides of the current collector is flush at one end and the other end. After the pole piece is wound, the paired energy cannot be fully exerted, resulting in low energy density of the electrode assembly. However, the coating method with both ends displaced is difficult to process and has high cost.

[0120] The setting of multiple pole ears improves the discharge performance of the pole piece, so that the electric energy on the current collector can be conducted through any pole ear, thereby avoiding the failure of the pole piece when a single pole ear is damaged. Moreover, after the current collector is partially broken, the electric energy at other positions of the current collector can still be transmitted through the pole ears, thereby reducing the probability of pole piece failure and further improving the performance of the pole piece.

[0121] In addition, based on the multi-electrode structure, the present application forms a single-sided coating area at one end of the pole piece by limiting the first coating area of ​​the pole piece to be flush with the second coating area at one end and staggered at the other end, thereby improving the energy density and charge and discharge performance of the battery at the same time.

[0122] It should be noted that the first pole piece 21 and the second pole piece 23 have opposite polarities, for example, the first pole piece 21 is an anode piece and the second pole piece 23 is a cathode piece, but not limited thereto. The first current collector 200a of the first pole piece 21 and the second current collector 200b of the second pole piece 23 are made of different materials.

[0123] In some embodiments, along the winding direction of the electrode assembly 20, at the starting end of the second pole piece 23, the first coating area 221b and the second coating area 231b of the second pole piece are misaligned, and at the ending end of the second pole piece 23, the first coating area 221b and the second coating area 231b of the second pole piece are flush; at the ending end of the first pole piece 21, the first coating area 221a and the second coating area 231a of the first pole piece are misaligned, and at the starting end of the first pole piece 21, the first coating area 221a and the second coating area 231a of the first pole piece are flush. This allows both the starting end and the ending end of the first pole piece 21 to achieve energy pairing with the second pole piece 23, thereby improving the energy density of the electrode assembly 20.

[0124] For example, Figure 4 The first electrode 21 is a first current collector 200a made of copper foil. Figure 5 yes Figure 4 The view at the first surface, Figure 6 The second electrode 23 is made of aluminum foil and the second current collector 200b is formed. Figure 7 yes Figure 6 The first pole piece 21 and the second pole piece 23 can be stacked and wound to form a structure Figure 8 An electrode assembly 20 according to one embodiment is shown.

[0125] It should be noted that: Figure 8 In the electrode assembly 20 shown, the starting end of the first pole piece 21 corresponds to the first end 24 of the first pole piece 21, and the ending end of the first pole piece 21 corresponds to the second end 25 of the first pole piece 21; the starting end of the second pole piece 23 corresponds to the first end 24 of the second pole piece 23, and the ending end of the second pole piece 23 corresponds to the second end 25 of the second pole piece 23.

[0126] In order to further improve the safety performance of lithium-ion batteries, a hollow foil area can be provided on the electrode. Please see below for details.

[0127] In some embodiments, Fig. 9 and Fig.11 As shown, at least one of the first end 24 and the second end 25 of the first pole piece 21 and the second pole piece 23 further includes a current collector with no active material on both sides, that is, at least one of the first end and the second end of the first pole piece further includes a current collector with no active material on both sides, and at least one of the first end and the second end of the second pole piece further includes a current collector with no active material on both sides. For the convenience of description, the current collector with no active material on both sides is defined as an empty foil area 400.

[0128] Specifically, Fig. 9As shown, at least one of the first end 24 and the second end 25 of the first electrode 21 further includes a first current collector 200a on both sides of which the first active material 300a is not disposed, that is, the first current collector 200a on which the first active material 300a is not disposed on the first surface 220a and the second surface 230a is an empty foil area 400. Fig.11 As shown, at least one of the first end 24 and the second end 25 of the second electrode sheet also includes a second current collector 200b on both sides of which the second active material 300b is not set, that is, the second current collector 200b on which the second active material 300b is not set on the first surface 220b and the second surface 230b is an empty foil area 400.

[0129] When the empty foil area 400 of the first electrode sheet is opposite to the empty foil area 400 of the second electrode sheet, they can act as a vest to improve the safety performance of the electrode assembly 20.

[0130] For example, Fig. 9 The first electrode is formed by using the first current collector 200a as a copper foil structure. Fig.10 for Fig. 9 A view at the first surface on Fig.11 The second electrode is a second electrode with the second current collector 200b being an aluminum foil. Fig.12 yes Fig.11 The first pole piece 21 and the second pole piece 23 can be stacked and wound to form a structure Fig.13 An electrode assembly 20 of an embodiment is shown. Along the winding direction of the electrode assembly 20, at the starting end of the second pole piece 23, the first coating area 221b and the second coating area 231b on the second pole piece 23 are misaligned, and at the tail end of the second pole piece 23, the first coating area 221b and the second coating area 231b on the second pole piece 23 are flush; at the tail end of the first pole piece 21, the first coating area 221a and the second coating area 231a on the first pole piece 21 are misaligned, and at the starting end of the first pole piece 21, the first coating area 221a and the second coating area 231a on the first pole piece 21 are flush, and the starting end and the tail end of the first pole piece 21 and the second pole piece 23 are both provided with an empty foil area 400, so as to play a vest role and improve the safety performance of the battery.

[0131] It should be noted that: Fig.13 In the electrode assembly 20 shown, the starting end of the first pole piece 21 corresponds to the first end 24 of the first pole piece 21, and the ending end of the first pole piece 21 corresponds to the second end 25 of the first pole piece 21; the starting end of the second pole piece 23 corresponds to the first end 24 of the second pole piece 23, and the ending end of the second pole piece 23 corresponds to the second end 25 of the second pole piece 23.

[0132] For example, Fig.14 The first electrode sheet 21 is formed by using the first current collector 200a as a copper foil structure. Fig.15 for Fig.14 A view at the first surface on Fig.16 The second electrode 23 is constructed of aluminum foil with the second current collector 200b. Fig.17 yes Fig.16 The first pole piece 21 and the second pole piece 23 can be stacked and wound to form a structure Fig.18 An electrode assembly 20 of an embodiment shown. Along the winding direction of the electrode assembly 20, at the starting end of the second pole piece 23, the first coating area 221b and the second coating area 231b on the second pole piece are misaligned, at the tail end of the second pole piece 23, the first coating area 221b and the second coating area 231b on the second pole piece are flush, and the starting end and the tail end of the second pole piece 23 are both provided with an empty foil area 400; at the tail end of the first pole piece 21, the first coating area 221a and the second coating area 231a on the first pole piece are misaligned, at the starting end of the first pole piece 21, the first coating area 221a and the second coating area 231a on the first pole piece are flush, and the tail end of the first pole piece 21 is provided with an empty foil area 400, and the starting end of the first pole piece 21 has no empty foil area 400, so that it can play a vest role and improve the safety performance of the lithium-ion battery.

[0133] It should be noted that: Fig.18 In the electrode assembly 20 shown, the starting end of the first pole piece 21 corresponds to the first end 24 of the first pole piece 21, and the ending end of the first pole piece 21 corresponds to the second end 25 of the first pole piece 21; the starting end of the second pole piece 23 corresponds to the second end 25 of the second pole piece 23, and the ending end of the second pole piece 23 corresponds to the first end 24 of the second pole piece 23.

[0134] In some embodiments, at least one of the first end 24 and the second end 25 of the first pole piece 21 or the second pole piece 23 is provided with an empty foil area 400. That is, one end of one of the first pole piece 21 and the second pole piece 23 is provided with an empty foil area.

[0135] For example, Fig.19 The first electrode sheet 21 is formed by using the first current collector 200a as a copper foil structure. Fig. 20 for Fig.19 A view at the first surface on Fig.21 The second electrode 23 is constructed with the second current collector 200b being an aluminum foil. Fig. 22 yes Fig.21 The first pole piece 21 and the second pole piece 23 can be stacked and wound to form a structure Fig.23An electrode assembly 20 of an embodiment is shown. Along the winding direction of the electrode assembly 20, at the starting end of the second pole piece 23, the first coating area 221b and the second coating area 231b on the second pole piece are misaligned, at the tail end of the second pole piece 23, the first coating area 221b and the second coating area 231b on the second pole piece are flush, and there is no empty foil area at the starting end and the tail end of the first pole piece 21; at the tail end of the first pole piece 21, the first coating area 221a and the second coating area 231a on the first pole piece are misaligned, at the starting end of the first pole piece 21, the first coating area 221a and the second coating area 231a on the first pole piece are flush, and the starting end and the tail end of the second pole piece 23 are both provided with an empty foil area 400, thereby improving the safety performance of the battery.

[0136] It should be noted that: Fig.23 In the electrode assembly 20 shown, the starting end of the first pole piece 21 corresponds to the first end 24 of the first pole piece 21, and the ending end of the first pole piece 21 corresponds to the second end 25 of the first pole piece 21; the starting end of the second pole piece 23 corresponds to the second end 25 of the second pole piece 23, and the ending end of the second pole piece 23 corresponds to the first end 24 of the second pole piece 23.

[0137] The embodiment of the present application further provides an electronic device, comprising the above-mentioned wound lithium-ion battery 100 .

[0138] The above-mentioned electronic device may be an electric car, a sweeping robot, a mobile phone or a tablet, etc.

[0139] The embodiment of the present application provides a wound lithium-ion battery and an electronic device, which improves the charge and discharge performance of the battery through the setting of a multi-pole ear structure, and can avoid battery failure when a single pole ear is damaged, thereby improving the safety performance of the battery. In addition, by setting a notch at the corner of the electrode assembly, the width of the pole piece can be increased, and the difference between the length of the shell and the length of the electrode assembly can be reduced, that is, the head space of the multi-pole ear structure is reduced, the energy density of the battery is improved, and the movement space of the battery when it falls is reduced, the risk of battery leakage is reduced, and the safety performance of the battery is improved.

[0140] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Under the concept of the present application, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other changes in different aspects of the present application as above, which are not provided in detail for the sake of simplicity. Although the present application has been described in detail with reference to the aforementioned embodiments, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned embodiments can still be modified, or some of the technical features can be replaced by equivalents. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A wound lithium-ion battery, comprising an electrode assembly, wherein the electrode assembly comprises a first electrode sheet, a separator and a second electrode sheet stacked and wound in sequence, characterized in that: The wound lithium-ion battery further comprises a shell, wherein the electrode assembly is accommodated in the shell; The first pole piece includes a first current collector and a plurality of first pole tabs electrically connected to the first current collector, and the second pole piece includes a second current collector and a plurality of second pole tabs electrically connected to the second current collector; The electrode assembly is flat, at least one corner of the shell is provided with a rounded corner, at least one corner of the electrode assembly is provided with a notch, and the notch corresponds to the rounded corner; The first pole piece has a first end and a second end opposite to each other, and the first pole piece further comprises a first active material; The first current collector comprises a first side and a first surface and a second surface opposite to each other, the first surface comprises a first coated area and a first uncoated area, the second surface comprises a second coated area, at the first end, the first coated area and the second coated area are flush, and at the second end, the first coated area and the second coated area are offset; The first active material is disposed in the first coating area and the second coating area; wherein each of the first pole tabs protrudes from the first side; and the first pole tab and the second pole tab both extend out of the housing; Wherein, along the winding direction of the electrode assembly, the width a of the notch is in the range of: 0.2 mm ≤ a ≤ 4 mm; Along the extending direction of the first electrode tab, the length b of the notch is in the range of: 0.3 mm ≤ b ≤ 4 mm; The range of the area c of the notch is: 0.05mm 2 ≤c≤5mm 2 .

2. The wound lithium-ion battery according to claim 1, characterized in that: Along the winding direction of the electrode assembly, the edge of the first pole piece is provided with a linear array of first notches, the edge of the second pole piece is provided with a linear array of second notches corresponding to and matching the first notches, and the first notches and the second notches together form the notch.

3. The wound lithium ion battery according to claim 1, characterized in that: The electrode assembly includes an upper end face and a lower end face relative to each other, and a flat portion and a bent portion connected between the upper end face and the lower end face; the first electrode ear extends out of the upper end face; the corner of the electrode assembly is located at the end of the bent portion, and the end of the bent portion is the intersection of the bent portion extending in a direction perpendicular to the upper end face and / or the lower end face and the upper end face and / or the lower end face.

4. The wound lithium ion battery according to claim 3, characterized in that: In the projection of the electrode assembly along its thickness direction, along the extension direction of the first electrode ear, the length L1 of the outermost edge of the bending portion and the main body length L2 of the electrode assembly satisfy 0.5mm≤L2-L1≤3mm; along the winding direction of the electrode assembly, the difference between the width of the upper end face and / or the lower end face and the main body width of the electrode assembly ranges from 0.3mm to 8mm; the main body length of the electrode assembly is the vertical distance between the upper end face and the lower end face; the main body width of the electrode assembly is the distance between the outermost projection edges of the two bending portions; the corners of the electrode assembly include the intersection of the extension line of the outermost projection edge of the bending portion and the upper end face and / or the lower end face.

5. The wound lithium ion battery according to claim 4, characterized in that: The second pole piece has a first end and a second end opposite to each other, and the second pole piece further comprises a second active material; The second current collector comprises a second side and a first surface and a second surface opposite to each other, the first surface of the second current collector comprises a first coating area and a first uncoated area, the second surface of the second current collector comprises a second coating area, at the first end of the second pole piece, the first coating area of ​​the second current collector and the second coating area of ​​the second current collector are flush, and at the second end of the second current collector, the first coating area of ​​the second current collector and the second coating area of ​​the second current collector are misaligned; The second active material is disposed on the first coating region of the second current collector and the second coating region of the second current collector; Wherein, each of the second pole tabs protrudes from the second side.

6. The wound lithium ion battery according to claim 5, characterized in that: Along the winding direction of the electrode assembly, at the tail end of the first pole sheet, the first coating area and the second coating area on the first pole sheet are offset.

7. The wound lithium ion battery according to claim 6, characterized in that: Along the winding direction of the electrode assembly, at the starting end of the second pole piece, the first coating area and the second coating area on the second pole piece are offset.

8. The wound lithium ion battery according to claim 6, characterized in that: The first end and the second end of the first pole piece both include current collectors with no active material layer on both sides.

9. The wound lithium ion battery according to claim 8, characterized in that: The first end and the second end of the second pole piece both include the second current collector without an active material layer on both sides.

10. The wound lithium ion battery according to claim 7, characterized in that: Along the winding direction of the electrode assembly, when the first coating area and the second coating area on the first pole sheet are misaligned at the tail end of the first pole sheet, and the first coating area and the second coating area on the second pole sheet are misaligned at the starting end of the second pole sheet, the tail end of the first pole sheet includes the first current collector without active material layers on both sides, and the tail end and starting end of the second pole sheet both include the second current collector without active material layers on both sides.

11. The wound lithium ion battery according to claim 1, characterized in that: The difference d between the length of the shell and the length of the electrode assembly is in the range of 1.8 mm≤d≤3.3 mm.

12. The wound lithium ion battery according to claim 1, characterized in that: The rounded corner is an outer convex corner, and the notch is an inner concave corner.

13. An electronic device, characterized in that: The invention comprises a wound lithium-ion battery as claimed in any one of claims 1 to 12.

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