CN112825381A

CN112825381A - Pole piece of secondary battery, preparation method of pole piece and secondary battery

Info

Publication number: CN112825381A
Application number: CN201911139155.2A
Authority: CN
Inventors: 张芹
Original assignee: Shenzhen Haihong New Energy Technology Co ltd
Current assignee: Xiamen Haichen New Energy Technology Co Ltd
Priority date: 2019-11-19
Filing date: 2019-11-19
Publication date: 2021-05-21

Abstract

The application provides a pole piece of a secondary battery, a preparation method of the pole piece and the secondary battery, and belongs to the technical field of secondary batteries. The pole piece comprises a current collector and a pole lug assembly. The tab assembly comprises a first tab and a second tab; the first tab comprises a first current collector connection area, the first current collector connection area covers and is connected to the outer surface of the first conductive layer, the second tab comprises a second current collector connection area, and the second current collector connection area covers and is connected to the outer surface of the second conductive layer. The junction of utmost point ear subassembly and mass flow body has first sunk area, and in first sunk area, the first mass flow body coupling region and the first conducting layer of first utmost point ear are range upon range of and imbed the insulating layer together and the surface of first mass flow body coupling region and first conducting layer is the concave surface, first conducting layer and second conducting layer at first sunk area electric connection. The arrangement of the pole piece can enable the connection between the pole lug and the current collector to be firmer, and the connection between the pole lug and the current collector has certain overcurrent capacity.

Description

Pole piece of secondary battery, preparation method of pole piece and secondary battery

Technical Field

The application relates to the technical field of secondary batteries, in particular to a pole piece of a secondary battery, a preparation method of the pole piece and the secondary battery.

Background

In the prior art, the composite current collector includes an insulating layer, and a first conductive layer and a second conductive layer respectively disposed on two surfaces of the insulating layer, and since the first conductive layer and the second conductive layer are connected through the insulating layer, and the insulating layer is non-conductive, a current on the first conductive layer cannot be directly conducted with a current on the second conductive layer. Therefore, it is necessary to arrange metal foils on the first conductive layer and the second conductive layer, respectively drain the metal foils, and then collect the metal foils onto the pole.

In the prior art, there is no effective connection between the first metal foil and the second conductive layer and between the second metal foil and the second conductive layer.

Disclosure of Invention

The application aims to provide a pole piece of a secondary battery, a preparation method of the pole piece and the secondary battery, the connection structure is more stable, and the connection effect is good.

In a first aspect, an embodiment of the present application provides a pole piece of a secondary battery, including a current collector and a tab assembly. The current collector comprises an insulating layer, and a first conducting layer and a second conducting layer which are respectively arranged on two surfaces of the insulating layer. The tab assembly comprises a first tab and a second tab; the first tab comprises a first current collector connection area, the first current collector connection area covers and is connected to the outer surface of the first conductive layer, the second tab comprises a second current collector connection area, and the second current collector connection area covers and is connected to the outer surface of the second conductive layer. The junction of utmost point ear subassembly and mass flow body has first sunk area, and in first sunk area, the first mass flow body coupling region and the first conducting layer of first utmost point ear are range upon range of and imbed the insulating layer together and the surface of first mass flow body coupling region and first conducting layer is the concave surface, first conducting layer and second conducting layer at first sunk area electric connection.

The first current collector connecting area is connected with the first conductive layer and can collect current on the first conductive layer to the first electrode lug. The second current collector connecting area is connected with the second conductive layer and can collect current on the second conductive layer to the second electrode lug. Because in the first sunken area, first mass flow body connecting region and first conducting layer embedding insulating layer and first mass flow body connecting region and the surface of first conducting layer are the concave surface, can make first conducting layer and second conducting layer electric connection in first sunken area department. That is, at the first recess region, the recessed first current collector connection region and the recessed first conductive layer press the insulating layer, so that the insulating layer at the first recess is diffused toward the periphery, and the insulating layer at the first recess penetrates, thereby electrically connecting the first conductive layer and the second conductive layer at the first recess region. Make first mass flow body connecting region, first conducting layer, second conducting layer and the connection of second mass flow body connecting region in first sunken department more firm, and can play certain effect of overflowing.

In one possible embodiment, the first current collector connection region, the first conductive layer, the second conductive layer, and the second current collector connection region are welded at the first recessed area.

The connection mode of the first sunken area is welding, so that the connection is firmer, the insulating layer is extruded at a welding spot, the integrity of the current collector can be guaranteed to a certain extent under the condition of guaranteeing the connection strength, the tensile strength of the lug assembly is guaranteed, the first conducting layer and the second conducting layer are welded, the peeling strength of the parts of the first conducting layer and the second conducting layer on the insulating layer and the peeling strength of the first lug and the second lug on the current collector are guaranteed.

In one possible embodiment, in the first recess region, the second current collector connection region and the second conductive layer are stacked and embedded together in the insulating layer and outer surfaces of the second current collector connection region and the second conductive layer are concave.

At the first depressed area, the outer surfaces of the first current collector connecting area and the first conductive layer are concave surfaces, the outer surfaces of the second current collector connecting area and the second conductive layer are also concave surfaces, and the two concave surfaces are opposite to each other to form the first depressed area. During welding, the welding teeth are arranged on the welding seat, the welding head is also provided with the welding teeth, the welding teeth on the welding seat and the welding teeth on the welding head need to be in one-to-one correspondence, and the welding strength is high.

In one possible embodiment, in the first recessed area, a surface of the second current collector connection region facing away from the second conductive layer is planar.

At the first recessed area, the outer surfaces of the first current collector connection area and the first conductive layer are concave surfaces, and the connection area of the second current collector is a plane. When welding, do not set up on the welding seat and weld the tooth, set up on the bonding tool and weld the tooth, need not weld the tooth and weld the correspondence between the tooth, the required precision of butt welder reduces, and can not appear welding the tooth and weld the tooth between the opposite grinding phenomenon, in the welded time, can avoid producing a large amount of metal dust, can reduce the volume of the metal powder that drops the pole piece surface among the welding process, avoid collecting of electric current to suffer the influence.

In one possible embodiment, in the first recess region, the second conductive layer is planar. Or in the first sunken area, the second conducting layer is embedded into the second current collector connecting area and the inner surface of the second conducting layer is a concave surface sunken towards the outer surface of the second current collector connecting area.

The second conducting layer and the first conducting layer are embedded into the second current collector connecting area, welding pressure and strength are larger, but the second current collector is not welded through, and welding strength is high.

In one possible embodiment, the first tab further comprises a first tab connection region connected to the first current collector connection region, and the second tab further comprises a second tab connection region connected to the second current collector connection region. The junction of first utmost point ear joining region and second utmost point ear joining region has the second depressed area, and in the second depressed area, first utmost point ear joining region and second utmost point ear joining region electric connection, and the surface in second utmost point ear joining region and/or the surface in first utmost point ear joining region are the concave surface.

In the second sunken area, the first pole lug is electrically connected with the second pole lug, so that the current collected on the first conducting layer and the current collected on the second conducting layer can be collected together through the first pole lug and the second pole lug, and the current collected on the pole piece can flow to the pole post. And the junction between first utmost point ear joining region and the second utmost point ear joining region is formed with the concave surface, has certain extrusion force between the two, and the connection effect is better.

In one possible embodiment, the first recessed area and the second recessed area are one solder print. First depressed area and second depressed area are one and weld the seal, weld seal department intensity higher, can play the supporting role to the first mass flow body coupling region and the first utmost point ear coupling region of utmost point ear and the junction of second mass flow body coupling region and second utmost point ear coupling region, and difficult emergence utmost point ear turns over and turns over, and welded size precision is changeed the control.

In one possible embodiment, the second pole lug further comprises a second pole post connection region having one end connected to an end of the second pole lug connection region distal from the second current collector connection region and another end protruding from the first pole lug connection region and configured to connect to a pole.

First utmost point ear and second utmost point ear are at second sunk area electric connection, can make the electric current of first utmost point ear department and the electric current of second utmost point ear department assemble in the second sunk area, and the second utmost point ear stretches out first utmost point ear joining region, and the second utmost point ear is connected with utmost point post, and first utmost point ear need not be connected with utmost point post, can reduce the welding number of piles between utmost point ear and the utmost point post, can reduce the welding thickness of utmost point ear, sparingly rolls over the height of utmost point ear, improves secondary battery's volume energy density.

In a second aspect, an embodiment of the present application provides a pole piece of a secondary battery, including: a current collector and a tab assembly. The current collector comprises an insulating layer, and a first conducting layer and a second conducting layer which are respectively arranged on two surfaces of the insulating layer. The tab assembly comprises a first tab and a second tab; first utmost point ear is including the first mass flow joining region and the first utmost point ear joining region of connecting, and the second utmost point ear is including the second mass flow joining region, second utmost point ear joining region and the second polar post joining region that connect gradually, and first mass flow joining region is connected with first conducting layer, and the second mass flow joining region is connected with the second conducting layer, and first utmost point ear joining region is connected with second utmost point ear joining region. The one end of keeping away from second utmost point ear joining region of second utmost point post joining region stretches out first utmost point ear joining region and is configured to be connected with utmost point post, is provided with the first through-hole that runs through the mass flow body between first mass flow body joining region and second mass flow body joining region, and first mass flow body joining region and second mass flow body joining region are at first through-hole department electric connection.

The first current collector connecting area is connected with the first conductive layer and can collect current on the first conductive layer to the first electrode lug. The second current collector connecting area is connected with the second conductive layer and can collect current on the second conductive layer to the second electrode lug. First utmost point ear joining region is connected with the second utmost point ear joining region, can make the electric current on the first utmost point ear collect together with the electric current on the second utmost point ear, and utmost point post is connected in rethread second utmost point post joining region, and the second utmost point ear is connected with utmost point post, and first utmost point ear need not be connected with utmost point post, can reduce the welding number of piles between utmost point ear and the utmost point post, can reduce the welding thickness of utmost point ear, sparingly rolls over the height of utmost point ear, improves secondary battery's volume energy density. Set up first through-hole on the mass flow body, first utmost point ear and second utmost point ear are at first through-hole department electric connection, can make first utmost point ear and second utmost point ear form the connection in through-hole department to improve the joint strength of first utmost point ear and second utmost point ear and mass flow body, and first utmost point ear and second utmost point ear are at the direct electric connection of first through-hole department, have increased the ability of overflowing between first utmost point ear and the second utmost point ear.

In one possible embodiment, the first current collector connection region and the second current collector connection region are both recessed towards the inside of the first through hole, such that the first current collector connection region and the second current collector connection region are welded.

The welding teeth are arranged on the welding head and the welding seat, so that the first lug and the second lug at the first through hole are both inwards sunken to form a stable welding spot, and the first lug and the second lug can be effectively welded.

In one possible embodiment, the first conductive layer, the insulating layer, and the second conductive layer of the current collector are soldered through to form a first via. In the process of welding the first lug and the second lug on the current collector, the current collector is directly welded completely, so that the first lug and the second lug are welded together at the first through hole, and the connection strength of the first lug and the second lug is high. And at the welding spot, the first tab and the second tab are connected with each other, so that the peel strength of the first tab and the second tab on the current collector is ensured, and the integrity of the current collector is also ensured.

In one possible embodiment, the inner surface of the first current collector connection region is provided with a first protrusion, the inner surface of the second current collector connection region is provided with a second protrusion, and the first protrusion and the second protrusion are both located in the first through hole and welded in the first through hole.

The first bulge of first utmost point ear and the second bulge of second utmost point ear form effective stable solder joint in first through-hole department, and the connection effect is better.

In a possible embodiment, the current collector further includes a first conductive connecting member disposed in the first through hole, one end of the first conductive connecting member is connected to the first current collector connecting region, and the other end of the first conductive connecting member is connected to the second current collector connecting region.

Through the setting of first electrically conductive connecting piece, can make first utmost point ear and second utmost point ear form effective connection in first through-hole department, and do not need first utmost point ear and second utmost point ear to carry out too much deformation, just can carry out effectual connection.

In one possible embodiment, an end of the first conductive connecting member, which is far away from the second current collector connecting region, sequentially passes through the first through hole and the first current collector connecting region and is connected with the first current collector connecting region.

The first conductive connecting piece penetrates through the first lug and is connected with the first lug, the connecting force of the first lug and the second lug in the thickness direction can be improved through the arrangement of the metal connecting piece, and the tensile strength of the second lug can be improved.

In one possible embodiment, the first conductive connecting member sequentially passes through the first current collector connecting region, the first through hole and the second current collector connecting region, and both ends of the first conductive connecting member are respectively connected with the first current collector connecting region and the second current collector connecting region.

First electrically conductive connecting piece had both passed first utmost point ear, had passed the second utmost point ear again, and the setting of metal connecting piece can further improve the joining force of first utmost point ear and second utmost point ear on thickness direction, can improve the tensile strength of first utmost point ear and second utmost point ear.

In one possible embodiment, a second through-opening is provided between the first tab connection region and the second tab connection region, said second through-opening extending through the first tab connection region and the second tab connection region. The second conductive connecting piece is arranged in the second through hole and connected with the first lug connecting area and the second lug connecting area.

Connect through second metal connecting piece between first utmost point ear joining region and second utmost point ear joining region, can make and effectively overflow between first utmost point ear and the second utmost point ear, and metal connecting piece's setting can improve the joining force of first utmost point ear and second utmost point ear in the thickness direction, improves the tensile strength of first utmost point ear and second utmost point ear.

In a third aspect, embodiments of the present application provide a secondary battery including a case and an electrode assembly. The electrode assembly is arranged in the shell and comprises a plurality of pole pieces of the secondary battery. Through the setting of above-mentioned secondary battery pole piece, can make the connection between utmost point ear and the mass flow body more firm, it is better to overflow the effect, and can increase secondary battery's volume energy density.

In a fourth aspect, an embodiment of the present application provides a method for manufacturing a pole piece of a secondary battery, where the method includes: and arranging the first current collector connecting area on the first conducting layer and the second current collector connecting area on the second conducting layer. And arranging a welding head on the outer surface of the first current collector connecting area, arranging a welding seat on the outer surface of the second current collector connecting area, applying pressure between the welding head and the welding seat to enable the insulating layer to be welded through, and butting the first conductive layer and the second conductive layer.

Through the welded mode, the insulating layer at solder joint department extrudees around to the solder joint, directly weld the insulating layer through, can make and form effective connection between first conducting layer and the second conducting layer, first utmost point ear and second utmost point ear are more firm in the connection of first sunk area, and the insulating layer is extruded in solder joint department, do not need punch the insulating layer earlier, or punch the mass flow body earlier, can keep the integrality of mass flow body to a certain extent under the circumstances of guaranteeing joint strength, the tensile strength of utmost point ear subassembly has been guaranteed, and first conducting layer and second conducting layer welding, the peel strength of the part on the insulating layer of first conducting layer and second conducting layer and the peel strength of first utmost point ear and second utmost point ear on the mass flow body have been guaranteed.

In a possible implementation mode, the pressure of the opposite top of the welding head and the welding seat is 2000-3500N, and the pressure is 3-4.5 GPa. The welding pressure and the welding pressure are selected, so that the insulating layer can be welded through, the occurrence of butt-grinding between the first conducting layer and the second conducting layer is avoided, the welding strength is good, and the service life is long.

In one possible embodiment, a plurality of welding teeth are provided on the welding base and/or a plurality of welding teeth are provided on the welding head.

If the welding seat and the welding head are both provided with a plurality of welding teeth, the welding teeth on the welding seat and the welding teeth on the welding head are in one-to-one correspondence, the first current collector connecting area and the second current collector connecting area are both sunken towards the current collectors in the first sunken areas, and the first conducting layer and the second conducting layer are welded. If not set up on the welding seat and weld the tooth, set up a plurality of welding teeth on the bonding tool, then first depressed part, the surface of first mass flow body and first conducting layer is sunken, need not weld the tooth and weld the correspondence between the tooth, and the required precision of butt welder reduces, and can not appear welding the tooth and weld the opposite grinding phenomenon between the tooth, and welded intensity is higher.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments are briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive efforts and also belong to the protection scope of the present application.

Fig. 1 is a first cross-sectional view of a pole piece provided in an embodiment of the present application;

fig. 2 is a cross-sectional view of a current collector and active material layer combination provided in an example of the present application;

fig. 3 is a plan view of a current collector combined with an active material layer provided in an example of the present application;

FIG. 4 is a plan view of a pole piece provided in an embodiment of the present application;

FIG. 5 is a second cross-sectional view of a pole piece provided in an embodiment of the present application;

FIG. 6 is a third cross-sectional view of a pole piece provided in an embodiment of the present application;

FIG. 7 is a fourth cross-sectional view of a pole piece provided in an embodiment of the present application;

FIG. 8 is a fifth cross-sectional view of a pole piece provided in an embodiment of the present application;

fig. 9 is a sixth cross-sectional view of a pole piece provided in an embodiment of the present application;

fig. 10 is a seventh cross-sectional view of a pole piece provided in an embodiment of the present application;

fig. 11 is an eighth cross-sectional view of a pole piece provided in an embodiment of the present application.

Icon: 1-pole piece; 10-a current collector; 20-a tab assembly; 30-an active material layer; 21-a first tab; 22-a second tab; 11-an insulating layer; 12-a first conductive layer; 13-a second conductive layer; 121-a first coating zone; 122-first polar ear region; 131-a second coating zone; 132-a second polar ear region; 211-a first current collector connection region; 212-a first tab connection area; 221-a second current collector connection region; 222-a second ear connection region; 223-a second pole column connection region; 40-a first recessed region; 50-a second recessed region; 60-welding and printing; 14-a first via; 2111-first projection; 2211-a second projection; 15-a first conductive connection; 16-a second via; 17-a second electrically conductive connection.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be described below with reference to the drawings in the embodiments of the present application.

The secondary battery comprises an electrode assembly and a shell, wherein the shell comprises a shell and a top cover plate, the electrode assembly is arranged in the shell, the top cover plate is covered on the shell, and a pole is fixed on the top cover plate. The electrode assembly includes a separator, and a positive electrode tab and a negative electrode tab located on both sides of the separator. The current on the pole piece is collected on the pole through the pole ear.

Fig. 1 is a first cross-sectional view of a pole piece 1 provided in this embodiment; fig. 2 is a cross-sectional view of the current collector 10 and the active material layer 30 provided in this embodiment in combination; fig. 3 is a plan view of the current collector 10 and the active material layer 30 provided in this embodiment in combination; fig. 4 is a plan view of the pole piece 1 provided in the present embodiment. Referring to fig. 1 to 4, in the embodiment of the present application, a pole piece 1 includes a current collector 10, a tab assembly 20, and an active material layer 30. The tab assembly 20 includes a first tab 21 and a second tab 22, and the first tab 21 and the second tab 22 may be made of copper foil or aluminum foil, or other conductive materials. The current collector 10 includes an insulating layer 11 and first and second conductive layers 12 and 13 respectively disposed on both surfaces of the insulating layer 11. The first conductive layer 12 has a first coated region 121 and a first polar ear region 122, and the second conductive layer 13 has a second coated region 131 and a second polar ear region 132. The active material layer 30 is applied to the first and

second coating regions

121 and 131.

The material of the insulating layer 11 may be PET (Polyethylene terephthalate), PEN (Polyethylene naphthalate), PI (Polyimide), PP (Polypropylene), PE (Polyethylene), non-woven fabric, and thin paper.

If the pole piece 1 is a positive pole piece, the first conductive layer 12 and the second conductive layer 13 may be aluminum plated layers, and the positive active material layer 30 is coated on the first coating region 121 of the first conductive layer 12 and the second coating region 131 of the second conductive layer 13. If the pole piece 1 is a negative pole piece, the first conductive layer 12 and the second conductive layer 13 may be copper-plated layers, and the negative active material layer 30 is coated on the first coating region 121 of the first conductive layer 12 and the second coating region 131 of the second conductive layer 13. Of course, the material of the first conductive layer 12 and the second conductive layer 13 is not limited to aluminum plating or copper plating, and the embodiment of the present application is not limited thereto.

With continued reference to fig. 1 and 4, the first tab 21 includes a first current collector connection region 211 and a first tab connection region 212 connected to each other, the second tab 22 includes a second current collector connection region 221, a second tab connection region 222 and a second pole connection region 223 connected to each other in sequence, the first current collector connection region 211 covers and is connected to the outer surface of the first tab region 122 of the first conductive layer 12, the second current collector connection region 221 covers and is connected to the outer surface of the second tab region 132 of the second conductive layer 13, the first tab connection region 212 extends out of the first conductive layer 12, the second tab connection region 222 extends out of the second conductive layer 13, the first tab connection region 212 is connected to the second tab connection region 222, and an end of the second pole connection region 223 away from the second tab connection region 222 extends out of the first tab connection region 212 and is configured to be connected to a pole.

That is to say, the first tab 21 is a short tab, the second tab 22 is a long tab, the short tab can transfer the current on the first conductive layer 12, the long tab can transfer the current on the second conductive layer 13, the long tab and the short tab are interconnected between the first tab connection area 212 and the second tab connection area 222, so that the current is collected to the long tab, the long tab is connected to the pole, and the collection of the current of the pole piece 1 to the pole is realized. Because long utmost point ear is connected with utmost point post, and on the electric current on the short utmost point ear had already gathered long utmost point ear, need not be connected between short utmost point ear and the utmost point post, so, compare in two isometric utmost point ears of output, only need connect long utmost point ear, connect the number of piles and can reduce half, can reduce the connection degree of difficulty. Meanwhile, the thickness of the tab assembly 20 at the connection position of the pole is reduced, so that the height of folded tabs can be saved, and the volume energy density of the battery is improved; the weight of the tab assembly 20 can also be reduced due to the halving of the number of layers, which can improve the weight energy density of the battery.

In order to weld the first tab connection region 212 of the first tab 21 and the second tab connection region 222 of the second tab 22 together. The first tab connection region 212 and the second tab connection region 222 are brought into contact and then welded. For example: the first tab 21 may be bent toward the second tab 22 to bring the first tab connection region 212 and the second tab connection region 222 into contact; the second tab 22 may be bent toward the first tab 21 so that the first tab connection region 212 and the second tab connection region 222 are in contact with each other; the first tab 21 may be bent toward the second tab 22, and the second tab 22 may be bent toward the first tab 21, so that the first tab connection region 212 and the second tab connection region 222 are in contact with each other.

Optionally, the length of the second pole connection region 223 is 5-40 mm, wherein the length refers to the length of the second tab 22 as shown in fig. 1, that is, the distance that the second tab 22 extends along the direction from the second current collector connection region 221 to the second pole connection region 223. The second pole connecting area 223 with the length is arranged, so that the influence of the end part (the remaining unwelded length of the first pole lug connecting area 212 is 1-5 mm) of the first pole lug connecting area 212 far away from the first current collector connecting area 211 on the welding between the second pole lug 22 and the pole can be avoided, and the problem that the length of the second pole lug 22 is too long to cause redundancy can also be avoided.

The first tab 21 may be a long tab, and the second tab 22 may be a short tab, which is not limited in this application.

In order to achieve a connection between the first tab 21 and the first conductive layer 12 and the second tab 22 and the second conductive layer 13. In the embodiment of the present application, the junction of the tab assembly 20 and the current collector 10 has a first recessed area 40, in the first recessed area 40, the first current collector connection region 211 and the first conductive layer 12 of the first tab 21 are stacked and embedded in the insulating layer 11 together, the outer surfaces of the first current collector connection region 211 and the first conductive layer 12 are concave, and the first conductive layer 12 and the second conductive layer 13 are electrically connected in the first recessed area 40.

Since the first tab 21 and the first conductive layer 12 are recessed in the first recessed area 40, the first conductive layer 12 and the second conductive layer 13 can be electrically connected in the first recessed area 40. That is, at the first recess region 40, the recessed first current collector connection region 211 and the recessed first conductive layer 12 press the insulating layer 11, so that the insulating layer 11 at the first recess is diffused toward the periphery, and the insulating layer 11 at the first recess is penetrated, thereby electrically connecting the first conductive layer 12 and the second conductive layer 13 at the first recess region 40. The first current collector connection region 211, the first conductive layer 12, the second conductive layer 13, and the second current collector connection region 221 are more firmly connected at the first recessed region 40, and can have a certain overcurrent effect.

Optionally, the first current collector connection region 211, the first conductive layer 12, the second conductive layer 13, and the second current collector connection region 221 are welded at the first recessed area 40. The connection of the first concave area 40 forms a welding point through welding, so that the connection is firmer, the insulating layer 11 is extruded at the welding point, the integrity of the current collector 10 can be ensured to a certain extent under the condition of ensuring the connection strength, the tensile strength of the tab assembly 20 is ensured, and the first conducting layer 12 and the second conducting layer 13 are welded, so that the peeling strength of the parts of the first conducting layer 12 and the second conducting layer 13 on the insulating layer 11 is improved. Meanwhile, the welding points formed by the first current collector connection region 211 and the second current collector connection region 221 in the first recessed area 40 ensure the peel strength of the first tab 21 and the second tab 22 on the current collector 10.

In the embodiment of the present application, a plurality of first recessed areas 40 may be formed on the first current collector connection area 211 and the second current collector connection area 221, and the plurality of first recessed areas 40 may be a plurality of welding spots, and the plurality of welding spots are arranged in an array, or arranged in other manners. The arrangement mode is related to the arrangement of the welding head or/and the welding teeth of the welding seat.

In order to weld the first tab 21, the first conductive layer 12, the second tab 22 and the second conductive layer 13 together at the first recessed area 40. A bonding tool is arranged on the outer surface of the first current collector connecting area 211, a welding seat is arranged on the outer surface of the second current collector connecting area 221, pressure is applied between the bonding tool and the welding seat, the insulating layer 11 is welded through, and the first conducting layer 12 is in butt joint with the second conducting layer 13.

By means of welding, the insulating layer 11 at the welding point is extruded to the periphery of the welding point, and the insulating layer 11 is directly welded through, so that effective connection can be formed between the first conductive layer 12 and the second conductive layer 13, and the connection between the first pole lug 21 and the second pole lug 22 in the first recessed area 40 is firmer. And the insulating layer 11 is extruded at the welding spot, and the insulating layer 11 does not need to be punched firstly, or the current collector 10 needs to be punched firstly, so that the integrity of the current collector 10 can be kept to a certain extent under the condition of ensuring the connection strength, the tensile strength of the tab assembly 20 is ensured, and the first conducting layer 12 and the second conducting layer 13 are welded, so that the peeling strength of the parts of the first conducting layer 12 and the second conducting layer 13 on the insulating layer 11 is ensured. Meanwhile, the welding points formed by the first electrode fluid connection region 211 and the second current collector connection region 221 in the first recessed area 40 ensure the peeling strength of the first tab 21 and the second tab 22 on the current collector 10.

The first tab 21, the first conductive layer 12, the second conductive layer 13 and the second tab 22 at the first recessed area 40 are welded together by welding. Not only can the first tab 21 and the first conductive layer 12 and the second tab 22 and the second conductive layer 13 form an effective connection, but also the current of the first conductive layer 12 is transferred to the first tab 21 and the current of the second conductive layer 13 is transferred to the second tab 22. There may also be some overcurrent effect at the solder joint where there may be some current transfer from the first conductive layer 12 to the second conductive layer 13 before it converges to the second pole ear 22.

Further, a plurality of solder points solder the first tab 21, the first conductive layer 12, the second conductive layer 13, and the second tab 22 at the plurality of first recessed areas 40. The parallel connection of a plurality of current paths between the first conductive layer 12 and the second conductive layer 13 of the current collector 10 can be realized, the overcurrent capacity can be met through a plurality of small welding points, and compared with a large welding point, the integrity of the insulating layer 11 of the current collector 10 can be kept to a relatively large degree by arranging a plurality of small welding points for connection, and the path of the current transferred from the conductive layer of the current collector 10 to the electrode lug is increased.

In order to weld the insulating layer 11 through by welding, the insulating layer 11 is extruded around the weld. In the embodiment of the application, the pressure of the opposite tops of the welding head and the welding seat is 2000-3500N, the pressure is 3-4.5 GPa, the welding mode can be ultrasonic welding, resistance welding can also be used, and the embodiment of the application is not limited as long as the welding penetration of the insulating layer 11 can be realized, and the protection range of the embodiment of the application is within the protection range of the embodiment of the application. Alternatively, the pressure of the welding may be 2000N, 2500N, 3000N, or 3500N; the weld pressure may be 3GPa, 3.5GPa, 4GPa or 4.5 GPa. In an embodiment, fig. 5 is a second cross-sectional view of the pole piece 1 provided in this embodiment. Referring to fig. 5, in the first recess area 40, the surface of the second current collector connection region 221 away from the second conductive layer 13 is a plane, and the second conductive layer 13 is a plane. One side of the first recess region 40 has a recess and one side has no recess. The welding seat is not provided with the welding teeth, the welding head is provided with a plurality of welding teeth, and one welding tooth can form a recess. That is, in the first recessed region 40, the second tab 22 and the second conductive layer 13 have no recessed structure, and the first tab 21 and the first conductive layer 12 have a recess in the direction toward the second tab 22, and the insulating layer 11 is welded through, and the insulating layer 11 is pressed around, so that the first conductive layer 12 and the second conductive layer 13 are welded. The welding head of the welding machine is required to be provided with welding teeth, and the welding seat is not required to be provided with welding teeth.

When welding, the welding teeth on the welding head can not be abraded with the welding teeth on the welding seat (the reason is that the welding seat is not provided with the welding teeth), the production of metal dust can be reduced, the amount of metal powder falling on the pole piece 1 can be greatly reduced, and the performance of a battery is prevented from being influenced. And the welding teeth are arranged on one side, so that the welding teeth on the welding seat do not need to correspond to the welding teeth on the welding head one by one, the processing precision of the welding machine can be reduced, the precision requirement of the corresponding position relation between the welding seat and the welding head is reduced, and the welding difficulty is reduced.

In another embodiment, fig. 6 is a third cross-sectional view of the pole piece 1 provided in this embodiment. Referring to fig. 6, in the first recessed area 40, a surface of the second current collector connection region 221 facing away from the second conductive layer 13 is a plane, the second conductive layer 13 is embedded in the second current collector connection region 221, and an inner surface of the second conductive layer 13 is a concave surface recessed toward an outer surface of the second current collector connection region 221. The surface of the second pole ear 22, which is away from the second conductive layer 13, has no recessed structure, the first pole ear 21 and the first conductive layer 12 have a recess facing the direction of the second pole ear 22, the second conductive layer 13 is recessed facing the direction of the second pole ear 22, the second conductive layer 13 at the first recessed area 40 is embedded into the second pole ear 22, the first pole ear 21, the first conductive layer 12 and the second conductive layer 13 are simultaneously extruded towards the direction of the second pole ear 22, the insulating layer 11 is welded through, the second conductive layer 13 is embedded into the second pole ear 22, the second pole ear 22 is not welded through, and the first recessed area 40 is firmly connected.

In other embodiments, at the first recess area 40, it is also possible that the first tab 21 and the first conductive layer 12 are not provided with recesses, and the second tab 22 and the second conductive layer 13 are provided with recesses. Optionally, the first conductive layer 12 and the first tab 21 are both planar; or the surface of the first tab 21 facing away from the first conductive layer 12 is a plane, and the first conductive layer 12 is embedded in the first tab 21.

In one embodiment, in the first recess region 40, the second current collector connection region 221 and the second conductive layer 13 are embedded in the insulating layer 11 and the outer surfaces of the second current collector connection region 221 and the second conductive layer 13 are concave. That is, at the first recess region 40, both surfaces have recesses embedded into the insulating layer 11, and the insulating layer 11 is pushed out to the periphery by the first conductive layer 12 and the second conductive layer 13, so that the first conductive layer 12 and the second conductive layer 13 are soldered.

Wherein, the height of welding the tooth is 60 ~ 200um, and the addendum length and the width of every welding tooth are 0.2 ~ 0.5 mm. The height of the welding teeth is high, so that the various welding points can be formed, and the plurality of first concave areas 40 are formed. For example: the height of the welding teeth can be 60um, 100um, 150um or 200 um; the length and width of the tip of the tooth may be 0.2mm, 0.3mm, 0.4mm or 0.5 mm.

To achieve the connection of the first tab connection region 212 and the second tab connection region 222, welding is an option. The junction of the first tab connection region 212 and the second tab connection region 222 has a second recessed area 50, the first tab connection region 212 and the second tab connection region 222 are electrically connected in the second recessed area 50, and the outer surface of the second tab connection region 222 and/or the outer surface of the first tab connection region 212 are/is concave.

Referring to fig. 1, 4-6, if the first recessed area 40 and the second recessed area 50 are a solder mark 60. That is to say, the connection between the first tab 21 and the first conductive layer 12, the connection between the second tab 22 and the second conductive layer 13, and the connection between the first tab 21 and the second tab 22 are completed at one time, and then the connection of the whole pole piece 1 is completed at one time, and the welding mark 60 of the obtained pole piece 1 is hard, so that the bottom of the tab (the connection between the current collector connection area of the tab and the tab connection area) can be supported, the tab is not easy to turn over in the continuous tape running process, and the welding size precision is easy to control. When the welding seat and the welding head are used for welding, the welding teeth at the upper end part of the welding head correspond to the first sunken areas 40, the welding teeth at the lower end part of the welding head correspond to the second sunken areas 50, and therefore welding of the pole piece 1 can be completed by one welding mark 60.

In order to form a solder print 60 on the pole piece 1, the direction of depression at the second depressed region 50 coincides with the direction of depression at the first depressed region 40. Namely, the first: if the surface of the second tab 22 facing away from the second conductive layer 13 is a plane at the first recessed area 40, the first tab 21 and the first conductive layer 12 are recessed toward the second tab 22, the insulating layer 11 is welded through, and the first conductive layer 12 and the second conductive layer 13 are welded, then the surface of the second tab 22 facing away from the first tab 21 is a plane at the second recessed area 50, the first tab 21 is recessed toward the second tab 22 and embedded in the second tab 22, and the second tab 22 is not welded through. And the second method comprises the following steps: if the second tab 22 and the second conductive layer 13 are recessed toward the insulating layer 11, the first tab 21 and the first conductive layer 12 are recessed toward the insulating layer 11, so that the insulating layer 11 is welded through, and the first conductive layer 12 and the second conductive layer 13 are welded in the first recessed area 40, the first tab 21 is recessed toward the second tab 22, and the second tab 22 is recessed toward the first tab 21, so that the cross section of the welding point is i-shaped in the second recessed area 50.

Further, the length of one welding stamp 60 is 2-6 mm, and the length of the welding position of the welding head and the welding seat where the welding teeth are arranged is 2-6 mm correspondingly (wherein, the length referred to herein refers to the distance that the welding stamp 60 extends along the direction from the second current collector connection region 221 to the second lug connection region 222). The amplitude requirement of the welding head can be met, the rigidity of the welding head can be guaranteed, and the welding strength is improved under the condition that the volumetric energy density is guaranteed.

Note that even if the recess direction of the first recess region 40 and the recess direction of the second recess region 50 coincide, welding may be performed using two passes of the solder marks 60. If the depression direction of the first depression region 40 and the depression direction of the second depression region 50 do not coincide, two passes of the solder stamp 60 are required for the welding. If the recessed direction of the first recessed area 40 is not consistent with the recessed direction of the second recessed area 50, welding teeth can be correspondingly arranged on the welding seat and the welding head respectively, the welding teeth on the welding seat are not corresponding to the welding teeth on the welding head, and welding of the pole piece 1 is achieved through one welding stamp 60. The embodiments of the present application are not limited.

Fig. 7 is a fourth cross-sectional view of the pole piece 1 provided in this embodiment; fig. 8 is a fifth cross-sectional view of the pole piece 1 provided in this embodiment. Referring to fig. 2, 7 and 8, a first through hole 14 penetrating the current collector 10 (penetrating the thickness direction of the current collector 10) is disposed between the first current collector connection region 211 and the second current collector connection region 221, and the first current collector connection region 211 and the second current collector connection region 221 are electrically connected at the first through hole 14. The first tab 21 and the second tab 22 can be connected at the first through hole 14, the connection strength between the first tab 21 and the current collector 10 and the connection strength between the second tab 22 and the current collector 10 can be improved, and the first tab 21 and the second tab 22 connected at the first through hole 14 also have certain overcurrent capacity, so that the current collection effect is better.

In one embodiment, with continued reference to fig. 7, the first current collector connection region 211 and the second current collector connection region 221 are both recessed into the first through hole 14, such that the first current collector connection region 211 and the second current collector connection region 221 are welded. The first pole lug 21 and the second pole lug 22 are both sunken towards the inside of the first through hole 14 in a welding mode, welding teeth are arranged on a welding seat and a welding head, the welding teeth and the welding teeth are correspondingly extruded towards the inside of the first through hole 14 during welding, materials in a pressed area are sunken towards the inside of the first through hole 14, and the first pole lug 21 and the second pole lug 22 which are contacted with each other in the first through hole 14 form a stable welding point.

Alternatively, the outer surfaces of the first and second

tab connection regions

212 and 222 are each formed with a recess, and welding is performed at the recessed location. Optionally, welding teeth are arranged on both the welding seat and the welding head, the welding seat is arranged on the outer surface of the first tab connection area 212 during welding, the welding head is arranged on the outer surface of the second tab connection area 222, pressure welding is performed between the welding head and the welding seat, the first tab connection area 212 is sunken towards the direction of the second tab connection area 222, the second tab connection area 222 is sunken towards the direction of the first tab connection area 212, and stable welding of the first tab connection area 212 and the second tab connection area 222 is achieved. Of course, the first tab connection region 212 may be recessed in the direction of the second tab connection region 222, and the outer surface of the second tab connection region 222 may be flat, or the outer surface of the first tab connection region 212 may be flat and the second tab connection region 222 may be recessed in the direction of the first tab connection region 212. The embodiments of the present application are not limited.

Alternatively, first through hole 14 may not be provided on current collector 10 first, but first conductive layer 12, insulating layer 11 and second conductive layer 13 of current collector 10 may be soldered through to form first through hole 14. In the process of welding the first tab 21 and the second tab 22 to the current collector 10, the current collector 10 is directly welded through, so that the first tab 21 and the second tab 22 are welded together at the first through hole 14, and the connection strength of the first tab 21 and the second tab 22 is high. And at the welding spot, the first tab 21 and the second tab 22 are connected with each other, so that the peeling strength of the first tab 21 and the second tab 22 on the current collector 10 is ensured, and the integrity of the current collector 10 is also ensured.

In another embodiment, with continued reference to fig. 8, the inner surface of the first current collector connection region 211 is provided with a first protrusion 2111, the inner surface of the second current collector connection region 221 is provided with a second protrusion 2211, and the first protrusion 2111 and the second protrusion 2211 are both located in the first through hole 14 and are welded in the first through hole 14. Welding teeth are not arranged on a welding head and a welding seat of the welding machine, through resistance welding (ultrasonic welding or other welding modes), the first pole lug 21 and the second pole lug 22 do not form a recess at the position of the first through hole 14 (the outer surfaces of the first pole lug 21 and the second pole lug 22 are both planes), a first protrusion 2111 is formed on the first pole lug 21, a second protrusion 2211 is formed on the second pole lug 22 (the inner surfaces of the first pole lug 21 and the second pole lug 22 both form protrusions), and the first protrusion 2111 and the second protrusion 2211 form stable and effective welding in the first through hole 14.

Alternatively, the first tab connection region 212 and the second tab connection region 222 may be welded by resistance welding without forming a recess. Note that, a depression may be formed at the first through hole 14 by welding, and the first tab connection region 212 and the second tab connection region 222 are not formed with a depression; alternatively, the first through-hole 14 may be welded by forming protrusions at both ends thereof without forming a recess, and the first tab connection region 212 and the second tab connection region 222 may be welded by forming a recess. All within the scope of protection of the present application.

In one embodiment, fig. 9 is a sixth cross-sectional view of the pole piece 1 provided in this embodiment. Referring to fig. 9, a first conductive connecting member 15 may be further disposed in the first through hole 14, wherein one end of the first conductive connecting member 15 is connected to the first current collector connecting region 211, and the other end is connected to the second current collector connecting region 221.

The first conductive connecting piece 15 is arranged in the first through hole 14, and then the first lug 21 and the second lug 22 are connected to two ends of the first conductive connecting piece 15 in a welding mode, so that the first lug 21 and the second lug 22 are stably connected, and the overcurrent effect between the first lug 21 and the second lug 22 is good.

Optionally, fig. 10 is a seventh cross-sectional view of the pole piece 1 provided in this embodiment. Referring to fig. 10, an end of the first conductive connection member 15 away from the second current collector connection region 221 sequentially passes through the first through hole 14 and the first current collector connection region 211 and is connected to the first current collector connection region 211. The first conductive connecting piece 15 and the second current collector connecting area 221 are integrally formed, the first conductive connecting piece 15 penetrates through the first through hole 14 and then is connected with the first current collector connecting area 211, and the first conductive connecting piece 15 penetrates through the first current collector connecting area 211 and is welded with the first tab 21 to form stable connection.

Optionally, fig. 11 is an eighth cross-sectional view of the pole piece 1 provided in this embodiment. Referring to fig. 11, the first conductive connecting member 15 sequentially passes through the first current collector connecting region 211, the first through hole 14 and the second current collector connecting region 221, and both ends of the first conductive connecting member 15 are respectively connected to the first current collector connecting region 211 and the second current collector connecting region 221. The first conductive connection member 15 passes through both the first current collector connection region 211 and the second current collector connection region 221, and is welded to the first tab 21 and the second tab 22, forming a stable connection.

Further, a second through hole 16 penetrating the first tab connection region 212 and the second tab connection region 222 is provided between the first tab connection region 212 and the second tab connection region 222. A second electrically conductive connection 17 is arranged in the second through-opening 16 and is connected to the first tab connection region 212 and the second tab connection region 222.

In the embodiment of the present application, each of the first through holes 14 and the second through holes 16 may be disposed in a plurality of numbers, the first through holes 14 are arranged in an array in the first current collector connection region 211 and the second current collector connection region 221, and the second through holes 16 are arranged in an array in the first tab connection region 212 and the second tab connection region 222, so as to improve the connection strength of the tabs and improve the overcurrent capability between the first tab 21 and the second tab 22.

According to the above, the pole piece 1 provided by the present application has the following beneficial effects:

(1) when the tab and the pole are connected, the tab and the pole are welded only by the long tab and the pole, the number of layers of the tab is halved, and the thickness of the tab is reduced, so that the volume energy density and the weight energy density of the battery are improved.

(2) And at the first concave area 40, the first collector connecting area 211 and the first polar ear area 122 of the first conductive layer 12 and the second collector connecting area 221 and the second polar ear area 132 of the second conductive layer 13 are welded, and the insulating layer 11 at the first concave area 40 is welded through, so that the insulating layer 11 is pressed to the periphery. The connection strength at the first recessed area 40 can be higher, and the first conductive layer 12 and the second conductive layer 13 have a certain overcurrent capacity at the first recessed area 40, so that the current collection effect is better, and the integrity of the current collector 10 is maintained to a certain extent.

(3) In the first recessed area 40, a surface of the second current collector connection region 221, which is away from the second conductive layer 13, is a plane, the second conductive layer 13 is embedded in the second current collector connection region 221, and the second conductive layer 13 is embedded in the second current collector connection region 221. In order to realize the structure, in the welding process, the welding teeth are not arranged on the welding seat, the welding teeth are arranged on the welding head, the welding process can be avoided, the phenomenon of butt-grinding between the welding teeth on the welding seat and the welding teeth on the welding head is further avoided, the butt-grinding between the first conductive layer 12 and the second conductive layer 13 can also be avoided, the first conductive layer 12, the second conductive layer 13, the first current collector connecting area 211, the second current collector connecting area 221, the first lug connecting area 212 and the second lug connecting area 222 can be avoided from being generated, more metal powder can be avoided, the risk that the metal powder falls on the pole piece 1 can be reduced, the connection effect of the lugs can be better, and the adverse effect of production caused by the falling of the metal powder on the performance of the battery can be avoided.

(4) A plurality of first depressed areas 40 form a plurality of solder joints, can reach the connection reliability of utmost point ear, can realize the parallelly connected of many places current path between the first conducting layer 12 of mass flow body 10 and the second conducting layer 13, just can satisfy the ability of overflowing through a plurality of little solder joints, and compare in a big solder joint, the mode that sets up a plurality of little solder joints and connect can keep the integrality of the insulating layer 11 of mass flow body 10 to a relatively great degree, and increase the route of mass flow body 10 conducting layer to utmost point ear switching current, the tensile strength of utmost point ear subassembly 20 has been improved simultaneously.

(5) The welding of first mass flow joining region 211, first conducting layer 12, second conducting layer 13 and second mass flow joining region 221, and the welding of first utmost point ear joining region 212 and second utmost point ear joining region 222 is a welding seal 60, and the welding of being connected between utmost point ear and mass flow body 10 and utmost point ear is once accomplished, can play the supporting role to utmost point ear bottom (the mass flow joining region of utmost point ear and the junction of utmost point ear joining region), in the continuous tape running in-process, the utmost point ear is difficult for turning over and rolling over, and welded dimensional accuracy is easily controlled.

(6) By providing the conductive connection member in the first through hole 14 of the current collector 10, the connection force in the thickness direction of the tab is stronger, and the tensile strength of the first tab 21 and the second tab 22 can be improved.

The above description is only a few examples of the present application and is not intended to limit the present application, and various modifications and changes may occur to those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A pole piece for a secondary battery, comprising:

the current collector comprises an insulating layer, and a first conducting layer and a second conducting layer which are respectively arranged on two surfaces of the insulating layer;

the tab assembly comprises a first tab and a second tab; the first tab comprises a first current collector connection area, the first current collector connection area covers and is connected to the outer surface of the first conductive layer, the second tab comprises a second current collector connection area, and the second current collector connection area covers and is connected to the outer surface of the second conductive layer;

the tab assembly with the junction of the mass flow body has first sunk area, first tab first mass flow body coupling region with first conducting layer is range upon range of and is embedded together the insulating layer just first mass flow body coupling region with the surface of first conducting layer is the concave surface, first conducting layer with the second conducting layer is in first sunk area electric connection.

2. The pole piece of the secondary battery according to claim 1, wherein the first current collector connection region, the first conductive layer, the second conductive layer, and the second current collector connection region are welded at the first recessed region.

3. The pole piece of the secondary battery according to claim 2, wherein in the first depressed area, the second current collector connection region and the second conductive layer are laminated and embedded together in the insulating layer and outer surfaces of the second current collector connection region and the second conductive layer are concave.

4. The pole piece of the secondary battery according to claim 2, wherein in the first recessed area, a surface of the second current collector connection region facing away from the second conductive layer is planar.

5. The pole piece of the secondary battery according to claim 4, wherein the second conductive layer is planar in the first depressed region;

or in the first sunken area, the second conducting layer is embedded into the second current collector connecting area and the inner surface of the second conducting layer is a concave surface sunken towards the outer surface of the second current collector connecting area.

6. The pole piece of the secondary battery according to any one of claims 1 to 5, wherein the first tab further comprises a first tab connection region connected to the first current collector connection region, and the second tab further comprises a second tab connection region connected to the second current collector connection region;

the junction of first utmost point ear joining region and second utmost point ear joining region has the second depressed area, first utmost point ear joining region with second utmost point ear joining region electric connection, just the surface in second utmost point ear joining region and/or the surface in first utmost point ear joining region is the concave surface.

7. The pole piece of the secondary battery according to claim 6, wherein the first depression region and the second depression region are one solder stamp.

8. The pole piece of the secondary battery of claim 6, wherein the second pole lug further comprises a second pole post connection region having one end connected to an end of the second pole lug connection region distal from the second current collector connection region and another end protruding from the first pole lug connection region and configured to connect to a pole post.

9. A pole piece for a secondary battery, comprising:

the tab assembly comprises a first tab and a second tab; the first lug comprises a first current collector connection area and a first lug connection area which are connected, the second lug comprises a second current collector connection area, a second lug connection area and a second pole column connection area which are sequentially connected, the first current collector connection area is connected with the first conductive layer, the second current collector connection area is connected with the second conductive layer, and the first lug connection area is connected with the second lug connection area;

keep away from of second pole post joining region the one end of second pole ear joining region stretches out first utmost point ear joining region and is configured into and is connected with utmost point post first mass flow body joining region with be provided with between the second mass flow body joining region and run through the first through-hole of mass flow body, first mass flow body joining region with second mass flow body joining region is in first through-hole department electric connection.

10. The pole piece of the secondary battery according to claim 9, wherein the first current collector connection region and the second current collector connection region are each recessed toward the inside of the first through hole, welding the first current collector connection region and the second current collector connection region.

11. The pole piece of the secondary battery of claim 10, wherein the first conductive layer, the insulating layer, and the second conductive layer of the current collector are soldered through to form the first via.

12. The pole piece of the secondary battery according to claim 9, wherein the inner surface of the first current collector connection region is provided with a first protrusion, the inner surface of the second current collector connection region is provided with a second protrusion, and the first protrusion and the second protrusion are both located in the first through hole and welded in the first through hole.

13. The pole piece of the secondary battery according to claim 9, further comprising a first conductive connector disposed in the first through hole, wherein one end of the first conductive connector is connected to the first current collector connection region and the other end is connected to the second current collector connection region.

14. The pole piece of the secondary battery according to claim 13, wherein an end of the first conductive connection piece, which is far from the second current collector connection region, sequentially passes through the first through hole and the first current collector connection region and is connected with the second current collector connection region.

15. The pole piece of the secondary battery according to claim 14, wherein the first conductive connecting member sequentially passes through the first current collector connecting region, the first through hole, and the second current collector connecting region, and both ends of the first conductive connecting member are connected to the first current collector connecting region and the first current collector connecting region, respectively.

16. The pole piece of the secondary battery according to any one of claims 13 to 15, wherein a second through hole penetrating the first tab connection region and the second tab connection region is provided between the first tab connection region and the second tab connection region;

the second conductive connecting piece is arranged in the second through hole and connected with the first lug connecting area and the second lug connecting area.

17. A secondary battery comprising a case and an electrode assembly disposed in the case, the electrode assembly comprising a plurality of pole pieces of the secondary battery according to any one of claims 1 to 16.

18. A preparation method of the pole piece of the secondary battery as claimed in any one of claims 2 to 8, characterized in that the preparation method comprises the following steps:

disposing the first current collector connection region to the first conductive layer and the second current collector connection region to the second conductive layer;

and arranging a welding head on the outer surface of the first current collector connecting area, arranging a welding seat on the outer surface of the second current collector connecting area, applying pressure between the welding head and the welding seat to enable the insulating layer to be welded through, and butting the first conductive layer and the second conductive layer.

19. The method of claim 18, wherein the pressure of the bonding tool against the bonding pad is 2000-3500N and the pressure is 3-4.5 GPa.

20. A method for manufacturing according to claim 19, wherein a plurality of welding teeth are provided on the welding shoe and/or a plurality of welding teeth are provided on the welding head.