Battery cell electrode connecting sheet as well as preparation method and application thereof

Abstract

The invention provides a battery cell electrode connecting piece and a preparation method and application thereof.The connecting piece comprises a first connecting area, a second connecting area and an arc-shaped bent area connected between the first connecting area and the second connecting area, and the thickness of the arc-shaped bent area is smaller than that of the first connecting area and that of the second connecting area; c-shaped notches are formed in the two ends, not connected with the first connecting area and the second connecting area, of the arc-shaped bending area respectively. The preparation method of the connecting piece comprises the steps of preforming, annealing and softening. The connecting piece disclosed by the invention can be applied to preparation of a battery cell and is used for connecting a cover plate and a roll core of the battery cell, so that the current of the roll core is led out to a cover plate pole. According to the connecting piece, the bending area can be accurately controlled, and even the bending position can have the cell short-circuit fusing function; and the preparation method of the connecting sheet is simple, and the prepared connecting sheet also has the characteristic of small gap after being bent by 180 degrees.

Description

Technical Field

[0001] The present invention belongs to the technical field of batteries, and in particular relates to a battery cell electrode connecting sheet and a preparation method and application thereof. Background Art

[0002] The battery cell is mainly composed of a cover plate, an aluminum shell and a winding core, and the cover plate and the winding core are connected by a connecting piece to conduct the current of the winding core to the cover plate pole. During the manufacturing process of the battery, the connecting piece needs to be folded into a 90° right angle, and one side of the connecting piece is welded to the winding core, and the other side is welded to the pole of the cover plate. After welding, the two sides of the connecting piece need to be folded 180° in parallel, so that the connecting piece can be stored between the winding core and the cover plate. At present, the preparation technology of the battery cell electrode connecting piece is usually to mechanically punch a rectangular groove of a certain depth at the bend to facilitate the bending of the connecting piece, but the connecting piece is difficult to accurately control the bending position when bending. After 180° bending, the gap between the connecting pieces is large, the available space inside the battery cell is reduced, and the volume energy density of the battery cell is reduced; and many batteries need to be separately provided with a structure with a fuse function, resulting in a battery structure that is not streamlined and high cost.

[0003] Patent application CN 114122631 A discloses a method for preparing a novel battery cell electrode adapter, including steps such as material preparation, pre-shaping at the bend, thinning at the bend, cutting the shape, bending at 90 degrees, surface cleaning and annealing and softening. The present invention thins the arc-shaped bending area of ​​the battery cell electrode adapter to a certain degree while ensuring the product's current capacity, and performs annealing and softening treatment after the battery cell electrode adapter is bent at 90 degrees to remove the stress, so that the bending hardness of the battery cell electrode adapter can be reduced to an appropriate degree, so that the battery cell electrode adapter is easy to operate when bent to 180 degrees, has good consistency, and does not crack at the bend. However, the battery cell electrode adapter disclosed in the patent application still has the problem of difficulty in accurately controlling the bending position when bending, and the preparation method of the battery cell electrode adapter is complicated to operate, and the gap between the connecting sheets after the battery cell electrode adapter is bent at 180° is not measured, and it is not mentioned whether the battery cell electrode adapter has a fuse function. Summary of the invention

[0004] The purpose of the present invention is to provide a battery cell electrode connecting sheet and its preparation method and application. The connecting sheet of the present invention can be used in the preparation of battery cells to connect the cover plate and the winding core of the battery cell to conduct the current of the winding core to the cover plate pole. The connecting sheet of the present invention can accurately control the bending area, and even make the bending part take into account the short-circuit fusing function of the battery cell; and the preparation method of the connecting sheet is simple, and the prepared connecting sheet also has the characteristic of small gap after 180° bending.

[0005] The purpose of the present invention is achieved through the following technical solutions:

[0006] In the first aspect, the present invention provides a battery cell electrode connecting sheet, which includes a first connecting area, a second connecting area, and an arc-shaped bending area connected between the first connecting area and the second connecting area, and the thickness of the arc-shaped bending area is smaller than the thickness of the first connecting area and the second connecting area, and C-shaped notches are respectively provided at both ends of the arc-shaped bending area that are not connected to the first connecting area and the second connecting area.

[0007] In some embodiments of the present invention, the thickness of the arc-shaped bending area decreases from thick to thin from the two end positions connected to the first connecting area and the second connecting area to the position away from the first connecting area and the second connecting area, preferably evenly; so that when the connecting piece is bent 180°, the thinnest part of the arc-shaped bending area becomes the deepest part of the bend.

[0008] In some embodiments of the present invention, the thickness of the position where the arc-shaped bending region is connected to the first connecting region is equal to the thickness of the first connecting region.

[0009] In some embodiments of the present invention, the thickness of the position where the arc-shaped bending region is connected to the second connecting region is equal to the thickness of the second connecting region.

[0010] In some embodiments of the present invention, the ratio of the thickness value of the thinnest position to the thickest position of the arc-shaped bending area is 1:(1.1-4).

[0011] In some embodiments of the present invention, through holes and / or non-through hole grooves are provided on the arc-shaped bending area; preferably, the through holes and / or non-through hole grooves are evenly distributed on the arc-shaped bending area.

[0012] In some embodiments of the present invention, when the connecting sheet is bent 180°, the non-through hole groove is located on the inner side of the bend.

[0013] In some embodiments of the present invention, the through hole may be a round hole, a square hole or other irregular through holes, such as a triangular hole, a pentagonal hole, a hexagonal hole, etc.

[0014] In some embodiments of the present invention, the through hole can be a through hole with a larger inner side and a smaller outer side at the bend when the connecting piece is bent 180°; or it can be a through hole with the same size inside and outside the bend when the connecting piece is bent 180°.

[0015] In some embodiments of the present invention, the non-through hole groove may be a groove of any shape, such as semicircular, semi-elliptical, square, etc.

[0016] In some embodiments of the present invention, the outer shape of the connecting piece when laid flat is configured to be L-shaped; that is, the first connecting area and the second connecting area are connected in an L-shape via an arc-shaped bending area.

[0017] In some embodiments of the present invention, the connecting sheet is made of aluminum or copper.

[0018] In some embodiments of the present invention, when the connecting sheet is made of aluminum, the hardness of the first connecting region and the second connecting region are the same or different, and are 20 to 40 HRC respectively.

[0019] In some embodiments of the present invention, when the connecting sheet is made of copper, the hardness of the first connecting region and the second connecting region are the same or different, and are 50 to 80 HV respectively.

[0020] In some embodiments of the present invention, when the material of the connecting sheet is aluminum, the thickness of the first connecting region and the second connecting region are the same or different, and are 0.6 to 2.0 mm respectively.

[0021] In some embodiments of the present invention, when the material of the connecting sheet is copper, the thickness of the first connecting region and the second connecting region are the same or different, and are 0.6-1.8 mm respectively.

[0022] In some embodiments of the present invention, the thickness of the arc-shaped bending area is 0.1-1 mm thinner than the thickness of the thinnest area in the first connecting area and the second connecting area; preferably, the thickness of the arc-shaped bending area is 0.5-1.9 mm.

[0023] In some embodiments of the present invention, the width of the arc-shaped bending area does not exceed 5 times the thickest thickness of the first connecting area and the second connecting area; for example, when the thickness of the first connecting area is 1 mm and the thickness of the second connecting area is 1.2 mm, the width of the arc-shaped bending area is ≤6 mm.

[0024] In some embodiments of the present invention, the width of the arc-shaped bending area is 3 to 5 mm.

[0025] In some embodiments of the present invention, the thinner the thickness of the first connecting region and the second connecting region is, the smaller the width of the arc-shaped bending region can be set to be, so as to make the gap between the first connecting region and the second connecting region and the winding core smaller after being bent.

[0026] In some embodiments of the present invention, the width of the C-shaped notch is ≤ the width of the arc-shaped bending area, preferably 2.5 to 5 mm.

[0027] In some embodiments of the present invention, the width of the C-shaped notch is equal to the width of the arc-shaped bending area.

[0028] In some embodiments of the present invention, when the width of the C-notch is less than the width of the arc-shaped bending area, the deepest line connecting the two C-notches on the arc-shaped bending area is the center line of the arc-shaped bending area along the width direction, so that when the connecting piece is bent 180° from the arc-shaped bending area and bent along the deepest line connecting the two C-notches, it is also bent along the center line of the arc-shaped bending area along the width direction.

[0029] In some embodiments of the present invention, after the connecting piece is bent 180° from the arc-shaped bending area, the gap between the first connecting area and the second connecting area is ≤2 mm, preferably ≤1.5 mm.

[0030] In a second aspect, the present invention provides a method for preparing the connecting sheet according to the first aspect, the preparation method comprising the following steps:

[0031] (I) Preforming: using copper sheet or aluminum sheet as raw material, a semi-finished connecting sheet having the outer shape and structure of the connecting sheet described in the first aspect is obtained by stamping or milling;

[0032] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace for vacuum annealing.

[0033] In some embodiments of the present invention, in step (I), the thickness of the aluminum sheet is 0.6-2.0 mm, and the thickness of the copper sheet is 0.6-1.8 mm.

[0034] In some embodiments of the present invention, the annealing treatment in step (II) is performed at a temperature of 300 to 750° C. and for a time of 30 to 360 min.

[0035] In some embodiments of the present invention, when the material of the connecting sheet is aluminum, the annealing temperature is 300-500° C. and the time is 30-360 min.

[0036] In some embodiments of the present invention, when the material of the connecting sheet is copper, the temperature of the annealing treatment is 500-750° C. and the time is 30-360 min.

[0037] In some embodiments of the present invention, the preparation method further comprises cooling the vacuum annealed connecting piece by nitrogen cooling after step (II); preferably, the cooling time is 30 min to 90 min.

[0038] In some embodiments of the present invention, the step (I) includes punching holes on the arc-shaped bending area; preferably, the punching includes punching through holes that penetrate the thickness and / or punching blind holes that do not penetrate the thickness; more preferably, the holes are evenly distributed on the arc-shaped bending area.

[0039] In some embodiments of the present invention, the blind hole that does not penetrate the thickness is drilled on the side that needs to be bent inwards.

[0040] In a third aspect, the present invention provides a use of the connecting sheet described in the first aspect or the connecting sheet prepared by the preparation method described in the second aspect in preparing a battery cell.

[0041] In a fourth aspect, the present invention provides a lithium-ion battery cell, which is composed of a cover plate, an aluminum shell and a winding core, and the cover plate and the winding core are connected by the connecting piece described in the first aspect or the connecting piece prepared by the preparation method described in the second aspect to conduct the current of the winding core to the cover plate pole.

[0042] In some embodiments of the present invention, the second connection area of ​​the connecting sheet is welded to the winding core by ultrasonic welding, and the first connection area of ​​the connecting sheet is welded to the cover plate by laser welding, so as to connect the winding core, the connecting sheet, and the cover plate to form a conductive path.

[0043] In some embodiments of the present invention, the connecting piece connecting the positive electrode column of the cover plate and the winding core is made of aluminum, and the connecting piece connecting the negative electrode column of the cover plate and the winding core is made of copper.

[0044] The beneficial effects of the present invention are as follows:

[0045] The thickness of the arc-shaped bending area of ​​the connecting piece of the present invention is less than the thickness of the first connecting area and the second connecting area, and C-shaped notches are respectively provided at the two ends of the arc-shaped bending area that are not connected to the first connecting area and the second connecting area. The C-shaped notch can play a bending guiding role when the connecting piece is bent 180°, so that the connecting piece can be bent as much as possible at the deepest connecting line position of the two C-shaped notches, thereby achieving more precise control of the bending area; especially when the thickness of the arc-shaped bending area changes from thick to thin from the two ends connected to the first connecting area and the second connecting area to the position away from the first connecting area and the second connecting area, the change in thickness can also play a bending guiding role, which can further achieve the bending of the connecting piece at the deepest connecting line position of the two C-shaped notches. At the same time, the design of the C-shaped notch and the thickness and thickness change design of the arc-shaped bending area can enable the connecting piece to have a short-circuit fuse function of the battery cell in the arc-shaped bending area. In addition, the connecting piece of the present invention can also be provided with through holes and / or non-through hole grooves on the arc-shaped bending area, thereby further shortening the short-circuit fuse time of the battery cell.

[0046] The connecting sheet preparation method of the present invention is simple, and an annealing softening treatment is added after the connecting sheet is processed and formed, so that the hardness of the connecting sheet after annealing can be strictly controlled, and the hardening effect of the arc bending area caused by processing, especially stamping forming, is reduced, and the precise control of the bending position is ensured. The gap between the first connection area and the second connection area after the connecting sheet is bent 180° is reduced, so as to increase the redundant space of the battery cell in the height direction of the aluminum shell, thereby improving the safety performance of the battery cell.

[0047] The connecting piece of the present invention can be used in the preparation of battery cells, and is used to connect the cover plate and the winding core of the battery cell to conduct the current of the winding core to the cover plate pole, especially in the industrial production of lithium-ion battery cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is a display diagram of the connecting sheet of the present invention when it is laid flat.

[0049] Figure 2 for Figure 1 The connecting piece is shown when it is bent 180°.

[0050] Figure 3 This is a display diagram of the connecting piece provided with a circular through hole 5 or a hemispherical groove 6 on the arc-shaped bending area 3 of the present invention when it is laid flat.

[0051] Marked in the attached drawings are: 1. first connection area, 2. second connection area, 3. arc-shaped bending area, 4. C-shaped notch, 5. through hole, 6. non-through hole groove. DETAILED DESCRIPTION

[0052] The following examples further illustrate the technology of the present invention. These examples are for illustration and example of the present invention and are not intended to limit the scope of the present invention in any form.

[0053] The endpoints and any values ​​of the ranges disclosed in the present invention are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be regarded as specifically disclosed in the present invention.

[0054] Example 1

[0055] A battery cell electrode connecting sheet, wherein the connecting sheet is arranged in an L shape when laid flat, as shown in the figure Figure 1 As shown, the connecting piece is bent 180° as shown in FIG. Figure 2The connecting piece comprises a first connecting area 1, a second connecting area 2 and an arc-shaped bending area 3 connected between the first connecting area 1 and the second connecting area 2, and the two ends of the arc-shaped bending area 3 not connected to the first connecting area 1 and the second connecting area 2 are respectively provided with C-shaped notches 4, and the thickness of the arc-shaped bending area 3 is uniformly reduced from thick to thin from the two ends connected to the first connecting area 1 and the second connecting area 2 to the position away from the first connecting area 1 and the second connecting area 2 (i.e., the midline of the arc-shaped bending area 3 along the width direction).

[0056] The first connection area 1 of the cell electrode connecting sheet is used to weld the connecting sheet to the cell cover, and the second connection area 2 is used to weld the connecting sheet to the cell winding core. The sizes of the first connection area 1, the second connection area 2 and the arc-shaped bending area 3 are designed or adjusted according to the structure of the winding core and the cover. The following is an example:

[0057] The first connection area 1 has a width of 25 mm, a length of 28 mm, and a thickness of 1 mm; the second connection area 2 has a width of 25 mm, a length of 58 mm, and a thickness of 1 mm; the arc-shaped bending area 3 is an arc groove with a width of 4 mm and a depth of 0.15 mm (equivalent to a thickness of 0.85 mm at the thinnest part of the arc-shaped bending area 3 and a thickness of 1 mm at the thickest part); the guide angle of the C-shaped notch 4 is R4; after the connecting piece is bent 180° at the arc-shaped bending area 3, the gap between the first connection area 1 and the second connection area 2 is 1 mm.

[0058] Example 2

[0059] A battery cell electrode connecting sheet, a display diagram of which when laid flat is as follows Figure 3 As shown, the connecting piece includes a first connecting area 1, a second connecting area 2, and an arc-shaped bending area 3 connected between the first connecting area 1 and the second connecting area 2. The two ends of the arc-shaped bending area 3 that are not connected to the first connecting area 1 and the second connecting area 2 are respectively provided with C-shaped notches 4. The thickness of the arc-shaped bending area 3 is uniformly changed from thick to thin from the two ends connected to the first connecting area 1 and the second connecting area 2 to the position away from the first connecting area 1 and the second connecting area 2 (i.e., the midline of the arc-shaped bending area 3 along the width direction). Through holes 5 and / or non-through hole grooves 6 are uniformly provided on the arc-shaped bending area; wherein, when the connecting piece is bent 180°, the non-through hole grooves 6 are located on the inner side of the bend.

[0060] The first connection area 1 of the cell electrode connecting sheet is used to weld the connecting sheet to the cell cover, and the second connection area 2 is used to weld the connecting sheet to the cell winding core. The sizes of the first connection area 1, the second connection area 2 and the arc-shaped bending area 3 are designed or adjusted according to the structure of the winding core and the cover. The following is an example:

[0061] The first connection area 1 has a width of 25 mm, a length of 28 mm, and a thickness of 1 mm. The second connection area 2 has a width of 25 mm, a length of 58 mm, and a thickness of 1 mm. The arc-shaped bending area 3 is a circular arc groove with a width of 4 mm and a depth of 0.15 mm (equivalent to a thickness of 0.85 mm at the thinnest part of the arc-shaped bending area 3 and a thickness of 1 mm at the thickest part). The guide angle of the C-shaped notch 4 is R4. After the connecting piece is bent 180° at the arc-shaped bending area 3, the gap between the first connection area 1 and the second connection area 2 is 1 mm. Two through holes 5 with a diameter of 4 mm are evenly arranged on the arc-shaped bending area 3, and the distance between the center positions of the two through holes 5 is 7 mm.

[0062] Example 3

[0063] The method for preparing the negative electrode connecting sheet comprises the following steps:

[0064] (I) Preforming: Take a copper sheet with a thickness of 1 mm and obtain a semi-finished connecting piece with the outer shape and structure of the connecting piece with the dimensions listed in Example 1 by stamping.

[0065] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace and subjected to vacuum annealing treatment at 600° C. for 80 minutes.

[0066] (III) Cooling: The connecting piece obtained in step (II) was placed in nitrogen and cooled for 60 minutes.

[0067] The hardness of the connection sheet prepared above was tested using the hardness HV standard, and the hardness of the first connection area 1 and the second connection area 2 was measured to be 70 HV.

[0068] Example 4

[0069] The method for preparing the positive electrode connecting sheet comprises the following steps:

[0070] (I) Preforming: Take an aluminum sheet with a thickness of 1 mm and obtain a semi-finished connecting piece with the outer shape and structure of the connecting piece with the dimensions listed in Example 1 by stamping.

[0071] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace and subjected to vacuum annealing treatment at 450° C. for 120 min.

[0072] (III) Cooling: The connecting piece obtained in step (II) was placed in nitrogen and cooled for 60 minutes.

[0073] The hardness of the connection sheet prepared above was tested using the HRC hardness standard, and the hardness of the first connection area 1 and the second connection area 2 was measured to be 33 HRC.

[0074] Example 5

[0075] A method for preparing a negative electrode connecting sheet comprises the following steps:

[0076] (I) Preforming: Take a copper sheet with a thickness of 1 mm and obtain a semi-finished connecting piece with the outer shape structure of the connecting piece with the size listed in Example 1 by milling.

[0077] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace and subjected to vacuum annealing treatment at 600° C. for 80 minutes.

[0078] (III) The connecting piece obtained in step (II) was placed in nitrogen and cooled for 60 minutes.

[0079] The hardness of the connection sheet prepared above was tested using the hardness HV standard, and the hardness of the first connection area 1 and the second connection area 2 was measured to be 70 HV.

[0080] Example 6

[0081] The method for preparing the positive electrode connecting sheet comprises the following steps:

[0082] (I) Preforming: Take an aluminum sheet with a thickness of 1 mm and obtain a semi-finished connecting sheet with the outer shape structure of the connecting sheet with the dimensions listed in Example 1 by milling.

[0083] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace and subjected to vacuum annealing treatment at 450° C. for 120 min.

[0084] (III) Cooling: The connecting piece obtained in step (II) was placed in nitrogen and cooled for 60 minutes.

[0085] The hardness of the connection sheet prepared above was tested using the HRC hardness standard, and the hardness of the first connection area 1 and the second connection area 2 was measured to be 33 HRC.

[0086] Example 7

[0087] The method for preparing the negative electrode connecting sheet comprises the following steps:

[0088] (I) Preforming: Take a copper sheet with a thickness of 1 mm and obtain a semi-finished connecting piece with the outer shape structure of the connecting piece with the size listed in Example 2 by milling.

[0089] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace and subjected to vacuum annealing treatment at 600° C. for 80 minutes.

[0090] (III) Cooling: The connecting piece obtained in step (II) was placed in nitrogen and cooled for 60 minutes.

[0091] The hardness of the connection sheet prepared above was tested using the hardness HV standard, and the hardness of the first connection area 1 and the second connection area 2 was measured to be 70 HV.

[0092] Example 8

[0093] The method for preparing the positive electrode connecting sheet comprises the following steps:

[0094] (I) Preforming: Take an aluminum sheet with a thickness of 1 mm and obtain a semi-finished connecting sheet with the outer shape structure of the connecting sheet with the dimensions listed in Example 2 by milling.

[0095] (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace and subjected to vacuum annealing treatment at 450° C. for 120 min.

[0096] (III) Cooling: The connecting piece obtained in step (II) was placed in nitrogen and cooled for 60 minutes.

[0097] The hardness of the connection sheet prepared above was tested using the HRC hardness standard, and the hardness of the first connection area 1 and the second connection area 2 was measured to be 33 HRC.

[0098] Example 9

[0099] A lithium-ion battery cell, which is composed of a cover plate, an aluminum shell and a winding core, wherein the negative electrode column of the cover plate and the winding core are connected by the connecting piece prepared in Example 3, and the positive electrode column of the cover plate and the winding core are connected by the connecting piece prepared in Example 4; wherein the connection is to weld the second connection area of ​​the connecting piece to the winding core by ultrasonic welding, and to weld the first connection area of ​​the connecting piece to the cover plate by laser welding.

[0100] After welding, the gap between the first connection area and the second connection area is less than 1 mm after the connecting piece is bent 180 degrees at the arc-shaped bending area 3. The finished lithium-ion battery cell was short-circuited for 40 seconds, and the cell was disassembled to find that the arc-shaped bending area 3 of the positive electrode connecting piece was melted.

[0101] Example 10

[0102] A lithium-ion battery cell, the lithium-ion battery cell consisting of a cover plate, an aluminum shell and a winding core, the negative electrode column of the cover plate and the winding core are connected by the connecting piece prepared in Example 5, and the positive electrode column of the cover plate and the winding core are connected by the connecting piece prepared in Example 6; wherein the connection is to weld the second connection area of ​​the connecting piece to the winding core by ultrasonic welding, and to weld the first connection area of ​​the connecting piece to the cover plate by laser welding.

[0103] After welding, the gap between the first connection area and the second connection area after the connecting piece was bent 180 degrees at the arc-shaped bending area 3 was less than 1.5 mm. The finished lithium-ion battery cell was short-circuited for 45 seconds, and the cell was disassembled to find that the arc-shaped bending area 3 of the positive electrode connecting piece was melted.

[0104] Embodiment 11

[0105] A lithium-ion battery cell, the lithium-ion battery cell consisting of a cover plate, an aluminum shell and a winding core, the negative electrode column of the cover plate and the winding core are connected by the connecting piece prepared in Example 7, and the positive electrode column of the cover plate and the winding core are connected by the connecting piece prepared in Example 8; wherein the connection is to weld the second connection area of ​​the connecting piece to the winding core by ultrasonic welding, and to weld the first connection area of ​​the connecting piece to the cover plate by laser welding.

[0106] After welding, the gap between the first connection area and the second connection area is less than 1 mm after the connecting piece is bent 180 degrees at the arc-shaped bending area 3. The finished lithium-ion battery cell was short-circuited for 40 seconds, and the cell was disassembled to find that the arc-shaped bending area 3 of the positive electrode connecting piece was melted.

[0107] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to the embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein, on the contrary, the present invention can be extended to all other methods and applications with the same functions.

Claims

1. A battery cell electrode connecting sheet, the connecting sheet comprising a first connecting area (1), a second connecting area (2), and an arc-shaped bending area (3) connected between the first connecting area (1) and the second connecting area (2), wherein the thickness of the arc-shaped bending area (3) is less than the thickness of the first connecting area (1) and the second connecting area (2), characterized in that: The two ends of the arc-shaped bending area (3) that are not connected to the first connecting area (1) and the second connecting area (2) are respectively provided with C-shaped notches (4).

2. The connecting piece according to claim 1, characterized in that: The thickness of the arc-shaped bending region (3) decreases from thick to thin from the two end positions connected to the first connecting region (1) and the second connecting region (2) to the position away from the first connecting region (1) and the second connecting region (2), preferably uniformly; more preferably, the ratio of the thickness value of the thinnest position to the thickest position of the arc-shaped bending region (3) is 1:(1.1-4); And / or, the arc-shaped bending area (3) is provided with through holes (5) and / or non-through hole grooves (6); preferably, the through holes (5) or non-through hole grooves (6) are evenly distributed on the arc-shaped bending area (3); And / or, the connecting piece is arranged to be L-shaped when laid flat.

3. The connecting piece according to claim 1 or 2, characterized in that: The connecting piece is made of aluminum or copper; preferably, When the material of the connecting plate is aluminum, the hardness of the first connecting region (1) and the second connecting region (2) are the same or different, and are 20 to 40 HRC respectively; when the material of the connecting plate is copper, the hardness of the first connecting region (1) and the second connecting region (2) are the same or different, and are 50 to 80 HV respectively; And / or, when the material of the connecting plate is aluminum, the thickness of the first connecting area (1) and the second connecting area (2) are the same or different, and are 0.6 to 2.0 mm respectively; when the material of the connecting plate is copper, the thickness of the first connecting area (1) and the second connecting area (2) are the same or different, and are 0.6 to 1.8 mm respectively.

4. The connecting sheet according to any one of claims 1 to 3, characterized in that: The thickness of the arc-shaped bending area (3) is 0.1 to 1 mm thinner than the thickness of the thinnest area between the first connecting area (1) and the second connecting area (2); preferably, the thickness of the arc-shaped bending area (3) is 0.5 to 1.9 mm; And / or, the width of the arc-shaped bending area (3) does not exceed 5 times the thickest thickness of the first connecting area (1) and the second connecting area (2); preferably, the width of the arc-shaped bending area (3) is 3 to 5 mm; And / or, the opening width of the C-shaped notch (4) is less than or equal to the width of the arc-shaped bending area (3), preferably 2.5 to 5 mm; And / or, after the connecting piece is bent 180° at the arc-shaped bending area (3), the gap between the first connecting area (1) and the second connecting area (2) is ≤2 mm, preferably ≤1.5 mm.

5. The method for preparing a connecting sheet according to any one of claims 1 to 4, characterized in that: The preparation method comprises the following steps: (I) Preforming: using copper sheet or aluminum sheet as raw material, a semi-finished connecting sheet having the external shape and structure of the connecting sheet according to claims 1 to 4 is obtained by stamping or milling; (II) Annealing and softening: The semi-finished connecting sheet obtained in step (I) is placed in a vacuum annealing furnace for vacuum annealing.

6. The preparation method according to claim 5, characterized in that: In step (I), the thickness of the aluminum sheet is 0.6 to 2.0 mm, and the thickness of the copper sheet is 0.6 to 1.8 mm; And / or, the annealing temperature in step (II) is 300-750°C and the time is 30-360 min; preferably, when the material of the connecting piece is aluminum, the annealing temperature is 300-500°C, and when the material of the connecting piece is copper, the annealing temperature is 500-750°C.

7. The preparation method according to claim 5 or 6, characterized in that: The preparation method further comprises cooling the vacuum annealed connecting piece by nitrogen cooling after step (II); preferably, the cooling time is 30 minutes to 90 minutes.

8. Use of the connecting sheet according to any one of claims 1 to 4 or the connecting sheet prepared by the preparation method according to any one of claims 5 to 7 in preparing a battery cell.

9. A lithium-ion battery cell, the lithium-ion battery cell comprising a cover plate, an aluminum shell and a winding core, characterized in that: The connecting piece according to any one of claims 1 to 4 or the connecting piece prepared by the preparation method according to any one of claims 5 to 7 connects the cover plate and the winding core to conduct the current of the winding core to the cover plate pole.

10. The lithium-ion battery cell according to claim 9, characterized in that: The second connection area (2) of the connection sheet is welded to the winding core by ultrasonic welding, and the first connection area (1) of the connection sheet is welded to the cover plate by laser welding.

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