CN113097656B

CN113097656B - Pole piece, battery core assembly and battery

Info

Publication number: CN113097656B
Application number: CN202110508502.5A
Authority: CN
Inventors: 李晓杰; 郭敏
Original assignee: Xiamen Hithium Energy Storage Technology Co Ltd
Current assignee: Xiamen Hithium Energy Storage Technology Co Ltd
Priority date: 2021-05-10
Filing date: 2021-05-10
Publication date: 2023-04-25
Anticipated expiration: 2041-05-10
Also published as: CN113097656A

Abstract

The application provides a pole piece, an electric core component and a battery, and relates to the technical field of lithium batteries. A pole piece, the tab of the pole piece is provided with a welding area, the welding area comprises a plurality of welding positions, and the thickness ratio of the thickness of the tab of the welding positions to the thickness of the non-welded part of the tab is (2-12): (3-30). The welding effect of this utmost point ear is better, avoids appearing the condition of overselding and rosin joint, and the resistance of utmost point ear is less, and the electric core has higher electric core capacity and longer cycle life.

Description

Pole piece, battery core assembly and battery

Technical Field

The application relates to the technical field of lithium batteries, in particular to a pole piece, an electric core component and a battery.

Background

With the development of science and technology, lithium ion batteries are increasingly applied to the fields of electric automobiles and the like, and the quality and performance of the lithium ion batteries are also receiving more and more attention. In lithium batteries, the tabs and the connecting pieces are mostly connected by welding. Ultrasonic welding or laser welding is generally adopted. In the welding process, the problem of cold joint or overseld is easy to generate, the connection between the tab and the connecting sheet is influenced, and the electrical properties of the pole piece and the battery cell are influenced.

Disclosure of Invention

The purpose of this application is to provide pole piece, electric core subassembly and battery to reduce the probability that the rosin joint or the overseld appear in the tab welding.

In a first aspect, an embodiment of the present application provides a pole piece, a tab of the pole piece has a welding area, the welding area includes a plurality of welding sites, and a thickness ratio of a thickness of the tab at the welding site to a thickness of a non-welded portion of the tab is (2-12): (3-30).

The tab of the pole piece that this application provided is the tab after the welding, and the thickness of tab compares in the tab that does not pass through the welding and reduces. The thickness variation of the tab has an influence on the electrical properties such as resistance of the pole piece. If the thickness of the tab is changed greatly, the welding pressure is possibly high, the power is too high, the crack of the conductive layer is increased, the resistance of the pole piece is increased, the IMP (alternating current resistance) of the battery cell is increased, and the capacity, multiplying power and cycle life of the battery cell are reduced. If the thickness variation of the tab is small, the welding effect may be too low, the welding is poor, and then the cold welding is performed. The same can result in an increase in pole piece resistance, an increase in cell IMP (alternating current resistance), and a decrease in cell capacity, a decrease in rate, and a decrease in cycle life. The inventor of the application finds that when the thickness ratio of the tab before and after welding is within the range of (2-12): (3-30), the welding effect of the tab is good, the conditions of over welding and cold welding are avoided, the resistance of the tab is small, and the battery cell has high battery cell capacity and long cycle life.

In one possible embodiment, the welding point has a region of extrusion at its periphery, the thickness of the tab of the region of extrusion, the thickness ratio of the tab of the welding point to the non-welded part of the tab being (4-32): (2-12): (3-30).

In the welding process, the thickness of the tab at the welding position is reduced, and extruded materials can bulge at the periphery of the welding position to form an extrusion area. The thickness of the extrusion region is large, so that the resistance of the tab is affected. The thickness change of the extrusion area after welding is in the range, the welding effect of the tab is good, and the resistance is small.

In one possible implementation, the tab includes a base film and conductive layers disposed on both sides of the base film, and the ratio of the thickness of the base film of the tab at the welded location to the thickness of the base film of the tab that is not welded is 4 (5-7).

In the welding process, the thickness of the base film and the thickness of the conductive layer can be changed, and the thickness of the base film can reflect the welding effect degree of the tab. The base film has better welding effect and smaller resistance in the thickness variation range of the electrode lugs.

In one possible implementation, the ratio of the thickness of the one-sided conductive layer of the tab of the weld site to the thickness of the one-sided conductive layer of the tab that has not been welded is (7-9): 10.

The thickness of the conductive layer has a larger influence on the thickness of the tab and the pole piece, and if the conductive layer is changed greatly, the overselding condition may occur, and if the conductive layer is changed less, the cold welding condition may occur. In the above thickness variation range, the resistance of the conductive layer is small.

In one possible implementation, the ratio of the resistance of the welded tab to the resistance of the unwelded tab is (5-6): 10. the resistance of the welded conductive layer is small through a proper welding process.

In a second aspect, a battery cell assembly is provided, including connection piece and battery cell, the battery cell includes above-mentioned pole piece, and connection piece and the utmost point ear welding of pole piece form a plurality of welding positions.

The battery cell component adopts the pole piece, the resistance of the battery cell component is smaller, and the battery cell resistance is smaller.

In one possible implementation, the tab includes a base film and conductive layers disposed on both sides of the base film, the conductive layer on one side of the base film and a connection sheet welded to the conductive layer form a transfer layer, and a ratio of a sum of thicknesses of the conductive layer and the connection sheet of the tab, which is not welded, to a thickness of the transfer layer is (7-8): 6.

Through welding process, the conducting layer is in the same place with the connection piece welding, and the degree of welding can be reflected to the thickness of the switching layer that forms, and in above-mentioned thickness variation range, the welding effect of utmost point ear is better, and resistance is less.

In one possible implementation manner, two sides of the tab are respectively provided with a connecting sheet, the tab and the connecting sheets on the two sides are welded to form a tab assembly, and the thickness ratio of the welded tab assembly to the non-welded tab assembly is 2 (3-5). In one possible implementation, two sides of the welding position are provided with extrusion areas, and the thickness of the tab area corresponding to the extrusion areas, the thickness ratio of the welded tab assembly to the non-welded tab assembly is 6:2 (3-5).

The tab assembly within the thickness proportion range is subjected to a proper welding process, so that the welding effect is not too low or too high, the situations of poor welding or overlarge welding power of the tab assembly are avoided, the increase of the resistance of the tab assembly after welding is avoided, the reduction of the cycle life is realized, and the electric core resistance is increased.

In a second aspect, a battery is provided, including a housing, an insulating member, a top cover assembly and the above-mentioned battery cell assembly, the battery cell assembly is accommodated in the interior of the housing, the insulating member is disposed between the battery cell and the housing, and the top cover assembly covers the housing and is connected with the battery cell through a tab.

The battery adopts the battery core component and has better capacitance and cycle life.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered limiting the scope, and that other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of a tab assembly according to an embodiment of the present disclosure;

fig. 2 is a schematic diagram of a detection resistor according to an embodiment of the present application.

Icon: 10-tab assembly; 100-electrode lugs; 101-welding position; 103-an extrusion zone; 110-base film; 120-a conductive layer; 200-connecting sheets.

Detailed Description

For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. The components of the embodiments of the present application, which are generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of the embodiments of the present application, as provided in the accompanying drawings, is not intended to limit the scope of the application, as claimed, but is merely representative of selected embodiments of the application. All other embodiments, which can be made by one of ordinary skill in the art based on the embodiments herein without making any inventive effort, are intended to be within the scope of the present application.

In the description of the present application, it should be noted that, the azimuth or positional relationship indicated by the terms "upper", "lower", etc. are based on the azimuth or positional relationship shown in the drawings, or the azimuth or positional relationship that is commonly put when the product of the application is used, are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element to be referred to must have a specific azimuth, be configured and operated in a specific azimuth, and therefore should not be construed as limiting the present application.

Some embodiments of the present application are described in detail below with reference to the accompanying drawings.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a battery cell assembly according to the present embodiment. The embodiment provides a battery cell assembly, which comprises a connecting sheet 200 and a battery cell, wherein the battery cell comprises a first polar pole piece, a second polar pole piece and a diaphragm arranged between the first polar pole piece and the second polar pole piece. Each pole piece (including the first polar pole piece and the second polar pole piece) is provided with a pole lug 100, and the current is led out through the connection between the pole lug 100 and the connecting sheet 200.

The first polar pole piece in the embodiment of the application is a pole piece containing a composite current collector, the composite current collector comprises a base film 110 and conductive layers 120 arranged on two sides of the base film 110, and active substances are coated on two sides of the composite current collector. The tab 100 of the first polar plate includes a base film 110 and conductive layers 120 disposed on two sides of the base film 110. In this embodiment, two connecting pieces 200 are respectively disposed on two sides of each tab 100, and the two connecting pieces 200 are welded with the tabs 100 to form the tab assembly 10. The connecting piece 200 in the embodiment of the present application is a metal piece.

The material of the base film 110 in the present application may be o-phenylphenol (OPP), polyethylene terephthalate (PET), polyimide (PI), polyphenylene sulfide (PPS), cast polypropylene (CPP), polyethylene naphthalate (PEN), polyvinyl chloride (PVC), preferably, the material of the base film 110 is PET, PPS or PEN. The base film 110 may be formed of any material or two or more materials. The material of the conductive layer 120 may be at least one selected from Ni, ti, cu, ag, au, pt, fe, co, cr, W, mo, al, mg, K, na, ca, sr, ba, si, ge, sb, pb, in, zn and its composition (alloy). The material of the conductive layers 120 on both sides of the base film 110 may be the same or different. The conductive layer 120 may be formed by a sputtering method, a vacuum deposition method, an ion plating method, a laser pulse deposition method, or the like.

Experimental researches show that the microstructure of the tab 100 and the connecting sheet 200 obtained after welding the tab 100 and the connecting sheet 200 by a certain welding process is closely related to the resistance characteristics, capacity, multiplying power and cycle life of the tab 100 after welding. The microstructure of the tab 100 and the tab 200 is described below.

After the connection piece 200 is welded with the tab 100, a welding area is formed on the tab 100. In the embodiment of the application, the welding is performed by adopting an ultrasonic welding or laser welding process, a plurality of welding positions 101 are formed in the welding area of the tab 100, and the tab 100 and the connecting sheet 200 are tightly connected at the welding positions 101. In this embodiment, the plurality of welding sites 101 are arranged in matrix, so that a certain distance exists between two or more welding sites 101, there is an unwelded position, the connection piece 200 is welded with the tab 100 or has a certain gap, and the specific structure is determined according to the welding degree of the welding sites 101. Before welding, the connection piece 200 is attached to the tab 100 in a contact manner, which means that the gap between the connection piece 200 and the tab 100 is small. After welding, a gap exists between the tab 100 and the tab 200, which are not welded, near the welding position 101.

When the thicknesses of the tab 100 and the connecting sheet 200 of the welding position 101 become smaller, the welding pressure is larger; the greater the welding pressure, the greater the gap between the tab 100 and the connection piece 200, which are not welded near the welding site 101, so that the flatness of the tab assembly 10 is worse. And meanwhile, the larger the welding pressure is, the more over-welding is likely to occur. When the thickness of the tab 100 and the connection piece 200 of the welding position 101 becomes smaller, which means that the welding pressure is smaller, the gap between the tab 100 and the connection piece 200, which are not welded near the welding position 101, is smaller, and the flatness variation is smaller. However, the condition of cold joint may occur due to small welding pressure, namely, poor welding effect and poor welding.

In some embodiments of the present application, the ratio of the thickness of the welded tab assembly 10 to the thickness of the non-welded tab assembly 10 is 2 (3-5). Further, in the welding process, the thicknesses of the tab 100 and the connection piece 200 of the welding site 101 become smaller, and correspondingly, the thicknesses of the tab 100 and the connection piece 200 near the welding site 101 become larger. During the welding process, the tab assembly 10 of the weld site 101 is reduced in thickness, and the material being extruded bulges around the weld site 101, forming the extrusion area 103. The extrusion region 103 has a large thickness, and thus affects the resistance of the tab assembly 10. In some embodiments of the present application, the thickness of the tab assembly 10 corresponding to the extrusion region 103, the thickness of the welded tab assembly 10, and the thickness ratio of the non-welded tab assembly 10 is 6:2 (3-5).

The inventor finds that the tab assembly 10 in the thickness proportion range is not too low or too high in welding effect through a proper welding process, so that poor welding or too high welding power of the tab assembly 10 is avoided, the resistance of the welded tab assembly 10 is prevented from being increased, the cycle life is reduced, and the cell resistance is prevented from being increased. Optionally, the thickness of the tab assembly 10 corresponding to the extrusion region 103, the thickness of the welded tab assembly 10, and the thickness ratio of the non-welded tab assembly 10 is 6:2:3 or 3:1:2 or 6:2:5.

In some embodiments of the present application, since the conductive layer 120 of the tab 100 and the connection piece 200 welded to the conductive layer 120 are both made of metal, after welding, the conductive layer 120 is tightly connected to the connection piece 200. In this embodiment, the conductive layer 120 and the connection pad 200 welded to the conductive layer 120 form a transfer layer. The ratio of the thickness of the welded transfer layer to the thickness of the unwelded transfer layer is 6 (7-8).

The conductive layer 120 and the connection layer in the thickness ratio range have better welding effect, and if the thickness ratio is lower than the ratio range, the welding pressure may be larger, the power is too high, which may cause the conductive layer 120 to crack to increase, further the resistance of the pole piece to increase, the battery cell IMP (alternating current resistance) to increase, and the capacity of the battery cell to decrease, the multiplying power to decrease and the cycle life to decrease. If the thickness ratio is higher than the ratio range, the welding effect may be too low, the welding may be poor, and the cold joint may occur. The same can result in an increase in pole piece resistance, an increase in cell IMP (alternating current resistance), and a decrease in cell capacity, a decrease in rate, and a decrease in cycle life.

In some embodiments of the present application, the ratio of the thickness of the tab 100 of the weld site 101 to the thickness of the tab 100 that has not been welded is (2-12): (3-30). The thickness of the tab 100 of the welding position 101 is smaller than that of the tab 100 which is not welded. The two sides of the welding position 101 are provided with the extrusion areas 103, the thickness of the tab 100 of the extrusion area 103, and the thickness ratio of the tab 100 of the welding position 101 to the tab 100 which is not welded is (4-32): 2-12): 3-30. Further, the ratio of the thickness of the base film 110 of the tab 100 of the weld site 101 to the thickness of the base film 110 of the tab 100 that has not been welded is (2-6): (3-9). The ratio of the thickness of the conductive layer 120 on one side of the tab 100 of the soldering bit 101 to the thickness of the conductive layer 120 on one side of the tab 100 which is not soldered is (7-9): 10.

After welding, the tab 100 and the conductive layer 120 in the thickness ratio range have smaller resistance, and the battery cell IMP is smaller, so that adverse effects on the tab and the battery cell caused by improper welding are avoided, and the electrical performance is reduced. Optionally, the ratio of the thickness of the base film 110 of the tab 100 of the welding site 101 to the thickness of the base film 110 of the tab 100 that is not welded is 2:3, 2:5, 2:6, 2:9, 3:5, 4:7, 4:9, 5:6, 5:8, 3:8, or 6:9. The thickness of the tab 100 of the extrusion region 103, the thickness of the tab 100 of the welding site 101, and the thickness ratio of the tab 100 that is not welded are 4:2:3 or 5:3:4 or 15:10:13. The ratio of the thickness of the conductive layer 120 on one side of the tab 100 of the welding position 101 to the thickness of the conductive layer 120 on one side of the tab 100 that is not welded is 9:10 or 8:10 or 7:10.

The thickness of the tab 100 and the connecting piece 200 in the present application is 50% of the thickness of the welding position 101, and fig. 1 is a cross-sectional view of the tab assembly 10 at 50% of the welding position 101.

The application also provides a battery (not shown), which comprises a shell, an insulating part, a top cover component and the battery cell component, wherein the battery cell component is contained in the shell, the insulating part is arranged between the battery cell and the shell, and the top cover component covers the shell and is connected with the battery cell through the lug 100. The battery adopts the battery core component and has better capacitance and cycle life.

The application provides a welding process of tab and connection piece with above-mentioned welded structure, adopts ultrasonic welding to weld, includes:

a40 KHz ultrasonic horn was used, the diameter of which was about 100mm. The tab and the connecting piece are welded under the conditions that the welding pressure (cylinder pressure) is 0.2-0.5MPa, the linear speed of the ultrasonic welding head is 30-50 m/min, and the amplitude of ultrasonic waves is 10-16 mu m. Alternatively, the welding pressure is 0.2MPa, 0.3MPa, 0.4MPa or 0.5MPa. The linear speed of the ultrasonic welding head is 30m/min, 35m/min, 40m/min, 45m/min or 50m/min. The amplitude of the ultrasonic wave is 10 μm, 12 μm, 13 μm, 15 μm or 16 μm.

Under the same other conditions, different ultrasonic welding pressures are adjusted to form different welding effects: the ultrasonic welding pressure is too high, and the welding head generates excessive pressure on the lug part of the welding part. Since the thickness of the tab portion material is only 50 μm, deformation, wrinkling and breakage are liable to occur, and the larger the welding pressure is, the larger the deformation is. When the deformation is large enough, the crack carding of the conductive layer on the current collector is gradually increased, and even the crack is directly converted into fracture, so that the conductive network is interrupted; when the welding pressure is too small, the welding head cannot be effectively attached to the welding lug due to insufficient physical attachment, so that ultrasonic energy cannot be conducted in time, cold joint is generated, the smaller the pressure is, the smaller the tensile test value is after welding, and a conductive network cannot be effectively formed.

The cracks generated by longitudinal pulling force on the surface of the welded lug can be determined by different linear speeds, when the ratio of the winding and unwinding speed of the pole piece to the rotating speed of the welding head is larger (such as larger than 1.3), the longitudinal pulling force on the surface can be excessively large, so that the conductive layer on the surface of the lug is stretched in the winding and unwinding direction, more cracks are generated, and when the ratio is larger, the conductive layer is broken, and the conductive network is broken.

The influence of the amplitude on the welding effect mainly lies in the effect of the ultrasonic energy, the amplitude is too large, the energy penetrability is strong, and the welding is easy to pass through; too small amplitude, insufficient energy penetration, and easy occurrence of cold joint.

The thickness of the composite current collector may be 5 μm to 15 μm, preferably 8 μm to 12 μm; the bond pad copper foil thickness may be 4 μm to 12 μm, preferably 6 μm to 10 μm. The thickness of the connecting piece is the thickness of the connecting piece on one side of the composite current collector.

The resistance value of the lug (composite current collector) of the single-layer pole piece obtained through the welding process is 20 omega-65 omega, and the tensile force is 5-80N. The IMP (alternating current resistance) of the 280 cells is 0.15mΩ -0.2mΩ. The resistance of the tab of the single-layer pole piece before welding is 33 omega-130 omega. The ratio of the resistance of the conductive layer of the soldered portion after soldering to the resistance of the conductive layer not soldered is (5-6): 10. the welded tab and the cell have good electrical performance.

The features and capabilities of the present application are described in further detail below in connection with the examples.

Example 1

The embodiment provides a battery cell assembly, which adopts the following process to transfer-weld the lugs:

the thickness of the composite current collector is 13 μm, wherein the polymer layer (base film) is 12 μm, the conductive layer is 1 μm, and the thickness of the aluminum foil of the connecting sheet is 13 μm. The thickness of the tab assembly was 40 μm.

The ultrasonic welding preset parameters are as follows: the diameter of the welding head is 100mm, the power of the welding machine is 40KHz, the pressure of a welding cylinder is 0.3MPa, the amplitude of ultrasonic waves is 16 mu m, and the linear speed of the welding head is 50m/min.

The thickness of the tab component corresponding to the welding position is 20 mu m, the thickness of the tab component corresponding to the extrusion area is 60 mu m, and the thickness of the tab component which is not welded is 40 mu m.

The thickness of the transfer layer corresponding to the welding position is 12 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 15 mu m.

The thickness of the tab at the welding position is 21.6 μm, and the thickness of the tab at the extrusion area is 24.6 μm.

The thickness of the conductive layer at the soldering site was 0.8. Mu.m, and the thickness of the polymer layer at the soldering site was 8. Mu.m.

The resistance of the tab before welding is 130mΩ, the resistance of the tab after welding is about 65mΩ, the tensile force is about 25N, the IMP of the cell is 0.18 Ω, and the DCR of the cell is 0.252 Ω.

Example 2

The ultrasonic welding preset parameters are as follows: the diameter of the welding head is 100mm, the power of the welding machine is 40KHz, the pressure is 0.4MPa, the amplitude is 16 mu m, and the speed is 50m/min.

The thickness of the tab component corresponding to the welding position is 15 mu m, the thickness of the tab component corresponding to the extrusion area is 65 mu m, and the thickness of the tab component which is not welded is 40 mu m.

The thickness of the transfer layer corresponding to the welding position is 9 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 14 mu m.

The thickness of the tab at the welding position is 16.4 μm, and the thickness of the tab at the extrusion area is 21.4 μm.

The thickness of the conductive layer at the soldering site was 0.7. Mu.m, and the thickness of the polymer layer at the soldering site was 6. Mu.m.

The resistance of the tab before welding is 130mΩ, the resistance of the tab after welding is about 80mΩ, the tensile force is about 19N, the IMP of the component cell is 0.19 Ω, and the DCR of the component cell is 0.266 Ω.

Example 3

The ultrasonic welding preset parameters are as follows: the diameter of the welding head is 100mm, the power of the welding machine is 40KHz, the pressure is 0.2MPa, the amplitude is 16 mu m, and the speed is 50m/min.

The thickness of the tab component corresponding to the welding position is 35 mu m, the thickness of the tab component corresponding to the extrusion area is 45 mu m, and the thickness of the tab component which is not welded is 40 mu m.

The thickness of the transfer layer corresponding to the welding position is 14 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 16 mu m.

The thickness of the tab at the welding position is 27.8 μm, and the thickness of the tab at the extrusion area is 29.8 μm.

The thickness of the conductive layer at the soldering site was 0.9. Mu.m, and the thickness of the polymer layer at the soldering site was 12. Mu.m.

The resistance of the tab before welding is 130mΩ, the resistance of the tab after welding is about 90mΩ, the tensile force is about 15N, the IMP of the component cell is 0.195 Ω, and the DCR of the component cell is 0.273 Ω.

Example 4

the thickness of the composite current collector is 5.5 mu m, wherein the polymer layer (base film) is 4.5 mu m, the conductive layer is 1 mu m, and the thickness of the aluminum foil of the connecting sheet is 8 mu m. The thickness of the tab assembly was 22.5 μm.

The ultrasonic welding preset parameters are as follows: the diameter of the welding head is 100mm, the power of the welding machine is 40KHz, the pressure is 0.3MPa, the amplitude is 16 mu m, and the speed is 50m/min.

The thickness of the tab component corresponding to the welding position is 14 mu m, the thickness of the tab component corresponding to the extrusion area is 28 mu m, and the thickness of the tab component which is not welded is 22.5 mu m.

The thickness of the transfer layer corresponding to the welding position is 10 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 11 mu m.

The thickness of the tab at the welding position is 15.6 μm, and the thickness of the tab at the extrusion area is 16.6 μm.

The thickness of the conductive layer at the soldering site was 0.8. Mu.m, and the thickness of the polymer layer at the soldering site was 4. Mu.m.

The resistance of the tab before welding is 40mΩ, the resistance of the tab after welding is about 20mΩ, the tensile force is about 19N, the IMP of the component cell is 0.16 Ω, and the DCR of the component cell is 0.224 Ω.

Example 5

The thickness of the tab component corresponding to the welding position is 8 mu m, the thickness of the tab component corresponding to the extrusion area is 32 mu m, and the thickness of the tab component which is not welded is 22.5 mu m.

The thickness of the transfer layer corresponding to the welding position is 5 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 9 mu m.

The thickness of the tab at the welding position is 9.4 μm, and the thickness of the tab at the extrusion area is 13.4 μm.

The thickness of the conductive layer at the soldering site was 0.7. Mu.m, and the thickness of the polymer layer at the soldering site was 3. Mu.m.

The resistance of the tab before welding is 40mΩ, the resistance of the tab after welding is about 25mΩ, the tensile force is about 18N, the IMP of the component cell is 0.165 Ω, and the DCR of the component cell is 0.231 Ω.

Example 6

The thickness of the tab component corresponding to the welding position is 20 mu m, the thickness of the tab component corresponding to the extrusion area is 24 mu m, and the thickness of the tab component which is not welded is 22.5 mu m.

The thickness of the transfer layer corresponding to the welding position is 8 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 13 mu m.

The thickness of the tab at the welding position is 14.3 μm, and the thickness of the tab at the extrusion area is 19.3 μm.

The thickness of the conductive layer at the soldering site was 0.9. Mu.m, and the thickness of the polymer layer at the soldering site was 4.5. Mu.m.

The resistance of the tab before welding is 40mΩ, the resistance of the tab after welding is about 30mΩ, the tensile force is about 10N, the IMP of the battery cell is 0.17 Ω, and the DCR of the battery cell is 0.238 Ω.

Example 7

the thickness of the composite current collector is 5.5 mu m, wherein the polymer layer (base film) is 4.5 mu m, the conductive layer is 1 mu m, and the thickness of the aluminum foil of the connecting sheet is 8 mu m.

The ultrasonic welding preset parameters are as follows: the diameter of the welding head is 100mm, the power of the welding machine is 40KHz, the pressure is 0.5MPa, the amplitude is 16 mu m, and the speed is 50m/min.

The thickness of the tab component corresponding to the welding position is 10 mu m, the thickness of the tab component corresponding to the extrusion area is 26 mu m, and the thickness of the tab component which is not welded is 22.5 mu m.

The thickness of the transfer layer corresponding to the welding position is 8 mu m, and the thickness of the transfer layer corresponding to the extrusion area is 11 mu m.

The thickness of the tab at the welding position is 13.6 μm, and the thickness of the tab at the extrusion area is 16.6 μm.

The resistance of the tab before welding is 40mΩ, the resistance of the tab after welding is about 24mΩ, the tensile force to the electrode is about 15N, the IMP of the component cell is 0.163 Ω, and the DCR of the component cell is 0.2282 Ω.

Example 8

The ultrasonic welding preset parameters are as follows: the diameter of the welding head is 100mm, the power of the welding machine is 60KHz, the pressure is 0.3MPa, the amplitude is 16 mu m, and the speed is 50m/min.

The thickness of the tab component corresponding to the welding position is 9 mu m, the thickness of the tab component corresponding to the extrusion area is 25 mu m, and the thickness of the tab component which is not welded is 22.5 mu m.

The resistance of the tab before welding is 40mΩ, the resistance of the tab after welding is about 23mΩ, the tensile force is about 16N, the IMP of the battery cell is 0.165 Ω, and the DCR of the battery cell is 0.231 Ω.

Test examples

Parameters of each thickness of the cell assemblies of examples 1 to 6 and parameters of the welding process are shown in the following table, and the electrical properties of the tabs obtained in examples 1 to 6 are detected by a method comprising:

the battery cells prepared from the pole pieces provided in examples 1-6 were selected, the number of the battery cells was 280, and the positive electrode was 105 layers and the negative electrode was 105 or 106 layers in a single battery cell. And respectively carrying out resistance detection on the corresponding battery cells.

Six welded single-layer pole pieces provided in examples 1-6 were selected, lugs with a size of 120×90 were selected, referring to fig. 2, two test points a and B were selected at two ends of the lug surface, and a resistance test probe was placed at A, B for detection.

And (3) detecting the cell resistance: IMP (alternating current resistance) was measured at an alternating current of 1KHZ/mΩ, with a standard of 0.10mΩ -0.20mΩ. DCR (direct current resistance) is detected under the condition of 500A DC/37A CC,30S,50%SOC,25 ℃ and BOL, wherein the standard is that DC is less than or equal to 0.5mΩ and CC is less than or equal to 0.5mΩ. The test results are shown in the following table:

TABLE 1 thickness parameters and welding process parameters and test results

/>

As can be seen from the detection results, in example 1, compared with example 2 and example 3, the welding process was more suitable, and the thicknesses of the tab, the connecting sheet, the conductive layer, the switching layer and the tab assembly in the welding position, the extrusion region and the non-welding region were within the ranges described in the present application, and the obtained tab resistance was reduced by half relative to the tab resistance before welding, which was smaller than that provided in example 2 and example 3. Description the microstructure of the tab assembly provided in example 1 has good electrical properties. The battery cell obtained by adopting the pole piece provided in the embodiment 1 has lower resistance, higher capacity and longer cycle life. Example 4 uses a more suitable welding process than examples 5 and 6, and has a better microstructure such that the resistance of the welded tab is less than that provided by examples 5 and 6. It can be seen that the battery cell obtained by the pole piece and welding process provided in example 4 has lower resistance, higher capacity and longer cycle life.

The foregoing description is only of the preferred embodiments of the present application and is not intended to limit the same, but rather, various modifications and variations may be made by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A pole piece, characterized in that a pole lug of the pole piece is provided with a welding area, a squeezing area and a part which is not welded, the welding area comprises a plurality of welding positions, the periphery of the welding position is provided with the squeezing area, the squeezing area is positioned between the welding position and the part which is not welded, and when in welding, the welding position is squeezed and the squeezing area is formed at the periphery of the welding position;

the thickness ratio of the tab of the extrusion area to the thickness of the tab of the welding position to the thickness of the non-welded part of the tab is (4-32): 2-12): 3-30.

2. The pole piece according to claim 1, wherein the tab comprises a base film and conductive layers arranged on two sides of the base film, and the ratio of the thickness of the base film of the tab at the welding position to the thickness of the base film of the tab which is not welded is 4 (5-7).

3. The pole piece of claim 2, wherein the ratio of the thickness of the conductive layer on one side of the tab of the weld site to the thickness of the conductive layer on one side of the tab that has not been welded is (7-9): 10.

4. A cell assembly comprising a connection tab and a cell, the cell comprising a pole piece according to any one of claims 1 to 3, the connection tab being welded to a tab of the pole piece.

5. The cell assembly of claim 4, wherein the tab comprises a base film and conductive layers disposed on both sides of the base film, the conductive layers on one side of the base film and the connection pads welded to the conductive layers form a transfer layer, and a ratio of a sum of thicknesses of the conductive layers of the tab and the connection pads, which are not welded, to a thickness of the transfer layer is (7-8): 6.

6. The cell assembly according to claim 4, wherein the connecting pieces are respectively arranged on two sides of the tab, the tab and the connecting pieces on two sides are welded to form a tab assembly, and the thickness ratio of the welded tab assembly to the non-welded tab assembly is 2 (3-5).

7. The cell assembly of claim 6, wherein the welding site has a crush zone at a periphery thereof, wherein a thickness of the tab assembly corresponding to the crush zone, a thickness ratio of the welded tab assembly to the non-welded tab assembly is 6:2 (3-5).

8. The cell assembly of claim 4, wherein the ratio of the resistance of the welded tab to the resistance of the non-welded tab is (5-6): 10.

9. a battery, characterized by comprising a shell, an insulating part, a top cover component and the battery cell component as claimed in any one of claims 4 to 8, wherein the battery cell component is contained in the shell, and the top cover component is covered on the shell and is connected with the battery cell component through a tab.