Battery cell, battery, and electric device

Abstract

A battery cell, a battery, and an electric device, which belong to the technical field of batteries. The battery cell comprises: a housing component, a terminal component, and an electrode assembly, wherein the terminal component comprises a conductive part; and the electrode assembly is accommodated in the housing component and comprises a tab part, the tab part comprises a plurality of stacked tab pieces, the plurality of tab pieces are connected to form a gathered part, the gathered part and the conductive part are stacked and connected to form a connection part, the gathered part comprises a compacted area, the connection part comprises a first portion formed on the gathered part, and at least most of the contour line of the first portion is located in the compacted area.

Description

Battery cells, batteries and electrical devices

[0001] Cross-reference to related applications

[0002] This application is based on and claims priority to Chinese Patent Application No. 202410405344.4, filed on April 3, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of battery technology, and in particular to a battery cell, a battery, and an electrical device. Background Technology

[0004] In recent years, new energy vehicles have experienced rapid development. In the field of electric vehicles, the power battery, as the power source, plays an irreplaceable and crucial role. The power battery comprises several individual battery cells; however, the reliability of these individual cells needs improvement.

[0005] Summary of the Invention

[0006] This application provides a battery cell, a battery, and an electrical device, which can improve the reliability of the battery cell.

[0007] In a first aspect, embodiments of this application provide a battery cell, including: a housing component, a terminal component, and an electrode assembly. The terminal component is disposed on the housing component and includes a conductive portion. The electrode assembly is housed in the housing component and includes a tab portion. The tab portion includes a plurality of tabs stacked together. The plurality of tabs are connected to form a converged portion. The converged portion is stacked with and connected to the conductive portion to form a connecting portion. The converged portion includes a compacted region. The thickness of the compacted region is less than the stacking thickness of the plurality of tabs in the tab portion. The connecting portion includes a first portion formed in the converged portion. At least a majority of the outline of the first portion is located in the compacted region.

[0008] In the above technical solution, since at least most of the outline of the portion of the connecting part formed on the converging part is located in the compaction area, the multi-layer electrode tabs in the compaction area are very tightly bonded together, which helps to improve the problem of thermal cracking in the outline of the connecting part, improves the conductivity and connection strength of the electrode tab and the conductive part, and enhances the overcurrent capacity and reliability of the battery cell.

[0009] In some embodiments, the connecting portion extends from the outer surface of the retractable portion toward the conductive portion, and the first portion includes a surface portion formed on the outer surface of the retractable portion.

[0010] In the above technical solution, by setting the extension direction of the connecting part to be from the closing part to the conductive part, it is easier for the welding head to be aligned with the closing part. This allows the welding head to reasonably design the welding trajectory based on the distribution of the compacted area and the loose area on the closing part, and accurately weld along the welding trajectory. This ensures that at least most of the outline of the part of the connecting part formed on the closing part can be reliably located in the compacted area, thereby effectively improving the conductivity and connection strength of the tab and the conductive part, and enhancing the current carrying capacity and reliability of the battery cell.

[0011] In some embodiments, at least a majority of the area of ​​the surface portion falls within the compacted region.

[0012] In the above technical solution, since the connecting part extends from the outer surface of the closing part towards the conductive part, and the internal part can extend from the surface part towards the conductive part, when at least most of the area of ​​the surface part falls into the compaction area, it is beneficial to increase the volume of the internal part falling into the compaction area. Since there are almost no interlayer gaps between the multilayer tabs in the compaction area, it is not easy for pores caused by interlayer gaps to appear in the molten pool in the compaction area, thereby reducing the pores formed in the internal part and improving the flow capacity of the connecting part.

[0013] In some embodiments, at least a majority of the outline of the surface portion falls within the compacted area.

[0014] In the above technical solution, by ensuring that at least a majority of the contour line of the surface portion falls within the compacted area, the problem of hot cracking in the weld contour of the connecting portion on the surface of the closing portion can be effectively improved. Furthermore, since the connecting portion extends from the outer surface of the closing portion towards the conductive portion, the contour line of the internal portion can extend from the contour line of the surface portion towards the conductive portion. When at least a majority of the contour line of the surface portion falls within the compacted area, it is beneficial to increase the proportion of the internal portion's contour line falling within the compacted area relative to falling within the loose area, thereby helping to improve the overall problem of hot cracking in the contour line of the connecting portion formed in the first part of the closing portion.

[0015] In some embodiments, more than 60% of the contour of the surface portion falls within the compacted area.

[0016] In the above technical solution, by ensuring that more than 60% of the contour line of the surface portion falls within the compacted area, the problem of hot cracking in the weld contour of the connecting part on the surface of the closing portion can be further improved. Furthermore, since the connecting part extends from the outer surface of the closing portion towards the conductive part, the contour line of the internal portion can extend from the contour line of the surface portion towards the conductive part. When more than 60% of the contour line of the surface portion falls within the compacted area, it is beneficial to further increase the proportion of the internal portion's contour line falling within the compacted area relative to falling within the loose area, thereby helping to further improve the problem of hot cracking in the contour line of the connecting part formed in the first part of the closing portion.

[0017] In some embodiments, the surface of the gathering portion is elongated, and the surface portion is elongated and matches the length direction of the gathering portion, with at least a majority of each of the two long sides of the surface portion located in the compacted area.

[0018] In the above technical solution, the surface portion can make full use of the space of the convergence portion, increase the area of ​​the surface portion, improve the current carrying capacity, and by setting at least most of each long side to be located in the compaction area, it is beneficial to increase the portion of the surface portion's outline that falls within the compaction area, improve the surface portion's outline thermal cracking problem, improve the conductivity yield and connection strength of the convergence portion and the conductive portion, and thus improve the reliability of the battery cell.

[0019] In some embodiments, the compaction area includes a first sub-region, which is elongated and matches the length and width directions of the gathering portion, respectively. The length of the first sub-region exceeds half the length of the gathering portion. There are two first sub-regions, which are spaced apart along the width direction of the gathering portion. The two long sides of the surface portion are respectively located in the two first sub-regions.

[0020] In the above technical solution, by setting the compaction area to include the two first sub-regions, and setting the two long sides of the surface portion of the connecting part in the two first sub-regions respectively, the length of the first sub-region is relatively large, and most of the contour line of the surface portion can fully utilize the compaction area. This further increases the portion of the surface portion's contour line falling within the compaction area, thereby further improving the problem of thermal cracking in the surface portion's contour, further improving the conductivity yield and connection strength between the convergence portion and the conductive portion, and thus enhancing the reliability of the battery cell. Moreover, when the internal portion extends from the surface portion towards the conductive portion, most of the internal portion can also fall into the first sub-region, which helps to increase the volume of the internal portion falling within the compaction area, further improving the problem of porosity in the internal portion, and thus further improving the current carrying capacity.

[0021] In some embodiments, each long side of the first sub-region has a plurality of protruding segments spaced apart along the length direction of the gathered portion, the protruding segments protruding toward the width direction of the gathered portion.

[0022] In the above technical solution, each long side of the first sub-region is uneven, which helps to improve the gripping force during welding, providing greater friction so that the first sub-region can be effectively compacted and the compaction rate of the first sub-region can be improved. Thus, when more of the laser weld seam contour falls on the first sub-region, the problem of hot cracking in that part of the contour can be further improved.

[0023] In some embodiments, the compaction region includes a plurality of second sub-regions disposed between two first sub-regions and spaced apart along the length direction of the converging portion. The protruding sections of the two first sub-regions are positioned opposite each other on one side, and two opposing protruding sections are respectively disposed between each pair of adjacent second sub-regions.

[0024] In the above technical solution, the space of the converging part can be further utilized to construct the compaction area. When the two long sides of the surface part are respectively located in the two first sub-regions, the surface part can cover at least part of the second sub-region, which is conducive to increasing the part of the laser weld that falls in the compaction area, further improving the problem of porosity in the molten pool of the laser weld, and further improving the flow capacity.

[0025] In some embodiments, the gathering portion includes a fluffy region, which includes a first fluffy area disposed between two first sub-regions and separated between the two first sub-regions and between the first sub-region and the second sub-region. The first fluffy area presents a linear form on the outer surface of the gathering portion so that the outline of the second sub-region matches the outline of the first sub-region.

[0026] In the above technical solution, by setting a first loose area in the form of lines to separate two first sub-regions, and separating the first sub-regions from the second sub-regions, the outline of the second sub-region matches the outline of the two first sub-regions. That is, the protruding position of the outline of the first sub-region corresponds to the concave position of the outline of the second sub-region. The distance between the two first sub-regions is small, and the distance between the first sub-regions and the second sub-regions is small, so that most of the area where the molten pool of the laser weld is located is a compacted area. This helps to improve the problem of porosity in the molten pool of the laser weld and further improves the flow capacity.

[0027] In some embodiments, the compaction region includes a plurality of third sub-regions, which are spaced apart and arranged around two first sub-regions.

[0028] In the above technical solution, by setting multiple third sub-regions around the two first sub-regions, it helps to improve the gripping force during welding, thereby providing greater friction and enabling the first sub-regions to be effectively compacted, thus improving the compaction rate of the first sub-regions. In this way, when part of the contour line of the laser weld falls into the first sub-region, the problem of hot cracking in that part of the contour line can be further improved.

[0029] In some embodiments, the gathering portion includes a fluffy region, which includes a second fluffy region disposed on the outer periphery of two first sub-regions and separated between the first sub-regions and the third sub-regions, and separated between two adjacent third sub-regions. The second fluffy region presents a linear form on the outer surface of the gathering portion so that the outline of the third sub-region matches the outline of the first sub-region.

[0030] In the above technical solution, by setting a second loose area in the form of lines to separate the first sub-region and the third sub-region, as well as to separate adjacent third sub-regions, the outline of the third sub-region matches the outline of the first sub-region. That is, the protruding position of the outline of the first sub-region corresponds to the concave position of the outline of the third sub-region. The distance between adjacent third sub-regions is small, and the distance between the first sub-region and the third sub-region is small. This allows for more full utilization of the space of the converging part to construct a compacted area, thereby improving the gripping force during welding, providing greater friction, and increasing the compaction rate of the first sub-region. In this way, when part of the outline of the laser weld falls on the first sub-region, the problem of hot cracking in that part of the outline can be further improved.

[0031] In some embodiments, the compacted region includes a plurality of first compacted rows spaced apart along the width direction of the gathered portion. Each first compacted row includes a plurality of fourth sub-regions spaced apart along the length direction of the gathered portion. Two long sides of the surface portion are respectively corresponding to two of the first compacted rows, and each long side passes through a plurality of fourth sub-regions in the corresponding first compacted row. The size of the fourth sub-region in the length direction of the gathered portion is greater than the distance between two adjacent fourth sub-regions in the length direction of the gathered portion.

[0032] In the above technical solution, by setting the compacted area as multiple fourth sub-regions including the above arrangement, and setting the dimension of the fourth sub-region in the length direction of the converging part to be greater than the distance between two adjacent fourth sub-regions in the length direction of the converging part, and by setting the two long sides of the surface portion of the connecting part corresponding to the two first compacted rows respectively, with each long side passing through multiple fourth sub-regions in the corresponding first compacted row, most of the contour line of the surface portion can fully utilize the compacted area, increasing the portion of the surface portion's contour line falling within the compacted area. This improves the problem of thermal cracking in the surface portion's contour, increases the conductivity yield and connection strength between the converging part and the conductive part, and thus enhances the reliability of the battery cell. Moreover, when the internal portion extends from the surface portion toward the conductive part, most of the internal portion can also fall into the fourth sub-region, thereby increasing the volume of the internal portion falling within the compacted area, further improving the problem of porosity in the internal portion, and further improving the current carrying capacity.

[0033] In some embodiments, there are two first compaction rows, the fourth sub-region is elongated, and the length direction of the fourth sub-region matches the width direction of the gathering part, the width direction of the fourth sub-region matches the length direction of the gathering part, and the length of the fourth sub-region exceeds one-quarter of the width of the gathering part.

[0034] In the above technical solution, the fourth sub-region can make full use of the space of the convergence part, and the area of ​​the fourth sub-region is relatively large. When the outline of the laser weld passes through multiple fourth sub-regions, it is beneficial to improve the problem of hot cracking in the outline of the laser weld and the problem of porosity in the molten pool of the laser weld, thereby improving the conductivity and connection strength of the convergence part and the conductive part.

[0035] In some embodiments, the gathering portion includes a fluffy region, which includes a third fluffy region separated between two adjacent fourth sub-regions in the same first compaction row, and a fourth fluffy region separated between two adjacent first compaction rows. The third fluffy region is in the form of a line extending along the width direction of the gathering portion on the outer surface of the gathering portion, and the fourth fluffy region is in the form of a line extending along the length direction of the gathering portion on the outer surface of the gathering portion. The width of the third fluffy region is smaller than the width of the fourth fluffy region.

[0036] In the above technical solution, it is beneficial to reduce the length of the long side of the surface portion falling within the third fluffy zone, which helps to further improve the problem of hot cracking in the surface portion's contour. Furthermore, since both the third and fourth fluffy zones exhibit a linear form on the outer surface of the converging portion, it is beneficial to increase the proportion of the fourth sub-region relative to the converging portion, i.e., to increase the proportion of the compacted region relative to the converging portion. Thus, when the contour line of the laser weld passes through multiple fourth sub-regions, it can improve the problem of hot cracking in the laser weld contour line and further improve the problem of porosity in the molten pool of the laser weld, thereby improving the flow capacity.

[0037] In some embodiments, the entire surface portion is located within the compacted area.

[0038] In the above technical solution, the entire contour of the surface portion is less prone to thermal cracking, effectively improving the conductivity and connection strength between the converged portion and the conductive portion, thus enhancing the reliability of the battery cell. Furthermore, since the connecting portion extends from the outer surface of the converged portion towards the conductive portion, when the entire surface portion is located within the compacted area, if the internal portion gradually tapers towards the conductive portion, it can also fall entirely within the compacted area. This further reduces the likelihood of thermal cracking in the contour of the internal portion, further improving the conductivity and connection strength between the converged portion and the conductive portion, and enhancing the reliability of the battery cell. Moreover, the internal portion is less prone to pores, further improving current carrying capacity.

[0039] In some embodiments, the compacted region includes a plurality of fifth sub-regions spaced apart, and the surface portion is a plurality of spaced-apart portions corresponding one-to-one with the plurality of fifth sub-regions.

[0040] In the above technical solution, by setting the compacted area as multiple fifth sub-regions with intervals, and setting multiple surface parts to correspond one-to-one with multiple fifth sub-regions, it is possible to simply and effectively realize that the entire surface part is located in the compacted area. Moreover, the total area of ​​the surface parts is relatively large, which meets the requirements of current carrying capacity. Furthermore, if the internal part has a shape that gradually decreases in size from the surface part to the conductive part, the internal parts extending from each surface part can also fall into the fifth sub-region respectively. This makes the outline of the internal part less prone to thermal cracking and less prone to pores, which is conducive to improving the conductivity and connection strength of the convergence part and the conductive part, improving the current carrying capacity, and enhancing the reliability of the battery cell.

[0041] In some embodiments, the compaction region includes a plurality of second compaction rows spaced apart along the width direction of the gathering portion, and each second compaction row includes a plurality of fifth sub-regions spaced apart along the length direction of the gathering portion.

[0042] In the above technical solution, by setting the compaction area as multiple fifth sub-regions including the above arrangement, the arrangement of the fifth sub-regions can be simplified, making it easier to accurately locate each fifth sub-region for laser welding. Moreover, it is beneficial to simplify the design of the compaction area, making the gathering part easier to process and reducing the design and processing difficulty of the welding head used to process the gathering part.

[0043] In some embodiments, there are two second compaction rows, and the fifth sub-region has a dimension in the width direction of the gathering portion and a dimension in the length direction of the gathering portion that both exceed one-quarter of the width of the gathering portion.

[0044] In the above technical solution, by setting two second compaction rows and setting the fifth sub-region to have dimensions in both the width direction and length direction of the gathering part exceeding one-quarter of the width of the gathering part, the area of ​​each fifth sub-region is relatively large, which helps to reduce the number of fifth sub-regions, reduce the number of welding operations, and make the area of ​​each surface part relatively large, which facilitates processing and improves flow capacity.

[0045] In some embodiments, the connecting portion includes a first connecting portion and a second connecting portion, the second connecting portion extending into the conductive portion, the extension depth of the first connecting portion being less than the extension depth of the second connecting portion, and the surface portion including a first facet formed by the first connecting portion on the outer surface of the gathering portion, and a second facet formed by the second connecting portion on the outer surface of the gathering portion, wherein at least a majority of the outline of the second facet is located within the first facet.

[0046] In the above technical solution, since the extension depth of the second connecting portion is relatively larger than that of the first connecting portion, the second connecting portion can extend into the conductive portion. Thus, a portion of the second connecting portion is formed in the closing portion, and the remainder is formed within the conductive portion. The second connecting portion serves to connect the closing portion and the conductive portion. Furthermore, since the extension depth of the first connecting portion is smaller than that of the second connecting portion, the energy required for laser welding of the first connecting portion is lower, and the contour of the first connecting portion is less prone to hot cracking. Also, since at least a majority of the contour line of the second face is located within the first face, at least a majority of the contour line of the second face on the outer surface of the closing portion can fall within the first face, thereby improving the problem of hot cracking of the contour line of the second face. Additionally, at least a portion of the contour line of the molten pool formed by the second connecting portion can also be located within the first connecting portion, further improving the problem of hot cracking of the molten pool contour of the second connecting portion and increasing the conductivity and connection strength between the conductive portion and the closing portion.

[0047] In some embodiments, the shape of the first face matches the outline shape of the second face, with at least a majority of the outline of the second face falling in the center of the first face.

[0048] In the above technical solution, by setting the shape of the first face to match the outline shape of the second face, it is beneficial to make the outline of the second face fall more within the first face, thereby further improving the problem of hot cracking of the outline of the second face. Furthermore, when laser welding is performed, the first connecting part and the second connecting part can respectively present a shape that extends and gradually shrinks along the thickness direction of the converging part. By setting at least most of the outline of the second face in the central position of the first face, it is beneficial to make the molten pool outline of the second connecting part extending into the converging part fall more within the first connecting part, thereby further improving the problem of hot cracking of the outline of the second connecting part.

[0049] In some embodiments, the surface of the gathering portion is elongated, and the surface portion is elongated and matches the length direction of the gathering portion. The first face is an elongated shape extending along the length direction of the gathering portion and two of them are spaced apart along the width direction of the gathering portion. The second face is an elongated shape extending along the length direction of the gathering portion, and the two long sides of the second face fall within the two first faces respectively.

[0050] In the above technical solution, one long side of the second face can fall within one of the first faces, and the other long side of the second face can fall within another first face. Thus, the two long sides of the second face can be located within the first connecting portion respectively. Most of the contour of the second face is less prone to hot cracking. Moreover, the molten pool contour extending from the two long sides of the second face into the converging portion can also be mostly located within the first connecting portion. This can improve the problem of hot cracking in the contour of the second connecting portion and improve the conductivity and connection strength between the converging portion and the conductive portion.

[0051] In some embodiments, there are multiple surface portions spaced apart, each surface portion including a first face and a second face, the first face being annular and surrounding a corresponding second face, and the outline of the second face being located within the corresponding first face.

[0052] In the above technical solution, the entire outline of the second face falls within the corresponding first face, so the outline of the second face is located within the first connecting part for the entire circumference. The outline of the second face is less prone to thermal cracking. Moreover, the molten pool outline extending from the outline of the second face into the converging part can also be mostly located within the first connecting part, thereby improving the problem of thermal cracking in the outline of the second connecting part and improving the conductivity and connection strength between the converging part and the conductive part.

[0053] In some embodiments, the extension depth of the first connection is 60%-100% of the thickness of the compacted region.

[0054] In the above technical solution, the first connecting portion extends only from the surface of the closing portion into the closing portion, and the extension depth exceeds half the thickness of the compacted area. In this case, the molten pool depth of the first connecting portion is relatively small, requiring less energy during welding, thus reducing the likelihood of hot cracking in the contour. This is beneficial for improving the conductivity and connection strength between the closing portion and the conductive portion. Furthermore, the molten pool depth of the first connecting portion is not too small, allowing the contour of the second connecting portion to fall more fully into the first connecting portion, thereby mitigating the problem of hot cracking in the contour of the second connecting portion.

[0055] In some embodiments, the connecting portion further includes a third connecting portion, the extension depth of the third connecting portion being less than the extension depth of the first connecting portion, the third connecting portion being disposed on the side of the first connecting portion away from the second connecting portion, and the surface portion further includes a third facet formed by the third connecting portion on the outer surface of the retracting portion, at least a portion of the outline of the first facet being located within the third facet.

[0056] In the above technical solution, since the extension depth of the third connecting part is less than that of the first connecting part, the energy required for the third connecting part during laser welding is smaller, and the contour of the third connecting part is less prone to hot cracking. Furthermore, since the third connecting part is located on the side of the first connecting part away from the second connecting part, at least a portion of the contour line of the first face is located within the third face, thereby improving the problem of hot cracking of the contour line of the first face. Additionally, at least a portion of the contour line of the molten pool formed by the first connecting part can also be located within the third connecting part, further improving the problem of hot cracking of the molten pool contour of the first connecting part and increasing the conductivity and connection strength between the conductive part and the closing part.

[0057] In some embodiments, at least a majority of the outline of the first face lies within the third face.

[0058] In the above technical solution, most of the contour of the first face can be repaired by the third connecting part, thereby more effectively improving the problem of thermal cracks in the contour of the first face.

[0059] In some embodiments, the shape of the third face matches the outline shape of the first face, with at least a majority of the outline of the first face falling in the center of the third face.

[0060] In the above technical solution, by setting the shape of the third face to match the outline shape of the first face, it is beneficial to make the outline of the first face fall more within the third face, thereby further improving the problem of hot cracking of the outline of the first face. Furthermore, when laser welding is performed, the first connecting part and the third connecting part can respectively present a shape that extends along the thickness direction of the converging part and gradually shrinks. By setting at least most of the outline of the first face in the central position of the third face, it is beneficial to make the molten pool outline of the first connecting part extending into the converging part fall more within the third connecting part, thereby further improving the problem of hot cracking of the outline of the first connecting part.

[0061] In some embodiments, the extension depth of the third connection is 20%-60% of the thickness of the compacted region.

[0062] In the above technical solution, the third connecting portion extends only from the surface of the closing portion into the closing portion, and the molten pool depth of the third connecting portion is relatively small. This requires less energy during welding, thus reducing the likelihood of hot cracking in the contour and improving the conductivity and connection strength between the closing portion and the conductive portion. Furthermore, the molten pool depth of the third connecting portion is not too small, allowing more of the contour of the first connecting portion to fall into the third connecting portion, thereby mitigating the problem of hot cracking in the contour of the first connecting portion.

[0063] In some embodiments, the first portion includes an internal portion formed within the gathering portion, at least a majority of the outline of the internal portion falling within the compacted area.

[0064] In the above technical solution, since at least most of the outline of the portion of the connecting part formed in the converging part is set in the compaction area, the multilayer electrode tabs in the compaction area are very tightly bonded together with no or almost no interlayer gaps. This can improve the problem of hot cracks in the weld outline caused by interlayer gaps, thereby improving the conductivity and connection strength of the electrode tab and the conductive part, and improving the reliability of the battery cell.

[0065] In some embodiments, more than 60% of the outline of the internal portion falls within the compacted area.

[0066] In the above technical solution, by setting more than 60% of the contour line of the internal part to fall within the compacted area, it is beneficial to further improve the problem of thermal cracking in the molten pool contour of the connecting part inside the closing part. Furthermore, when the connecting part extends from the outer surface of the closing part towards the conductive part, most of the contour line of the first part is the contour line of the internal part. Since more than 60% of the contour line of the internal part falls within the compacted area, it is beneficial to increase the proportion of the first part's contour line falling entirely within the compacted area relative to falling within the loose area. This can comprehensively improve the problem of thermal cracking in the contour line of the first part where the connecting part is formed in the closing part, further improving the conductivity and connection strength between the tab and the conductive part, and enhancing the reliability of the battery cell.

[0067] In some embodiments, at least a majority of the volume of the internal portion falls within the compacted area.

[0068] In the above technical solution, since there is no or almost no interlayer gap between the multilayer tabs in the compaction area, it is not easy for pores caused by interlayer gaps to appear in the molten pool in the compaction area. This embodiment, by setting at least most of the volume of the internal part in the compaction area, helps to reduce the pores formed in the internal part, thereby improving the flow energy of the connection part.

[0069] In some embodiments, the area of ​​the compacted region relative to the converging region is greater than or equal to 40%.

[0070] In the above technical solution, by setting the area ratio of the compacted region to be greater than or equal to 40%, it is beneficial to increase the coverage of the compacted region on the gathering part, which is conducive to the design of the connection part. This allows the connection part to be more distributed in the compacted region, improves the problem of thermal cracking in the outline of the connection part, improves the conductivity and connection strength of the tab and the conductive part, improves the problem of pores in the connection part, and improves the current carrying capacity of the connection part, thereby improving the reliability of the battery cell.

[0071] In some embodiments, the area of ​​the compacted region relative to the converging region is greater than or equal to 60%.

[0072] In the above technical solution, by setting the area ratio of the compacted region to be greater than or equal to 60%, most of the converging part can be a compacted region, which is beneficial to the design of the connection part. This allows the connection part to be more distributed in the compacted region, improves the problem of thermal cracking in the outline of the connection part, improves the conductivity and connection strength of the tab and the conductive part, improves the problem of pores in the connection part, and improves the current carrying capacity of the connection part, thereby improving the reliability of the battery cell.

[0073] In some embodiments, the compaction rate of the compacted area is greater than or equal to 6%.

[0074] In the above technical solution, by setting the compaction rate of the compaction zone to be greater than or equal to 6%, the interlayer gap in the compaction zone can be reduced, the part of the connector entering the compaction zone is less prone to thermal cracks and pores, the overall flow capacity of the connector is improved, and the reliability and conductivity of the connector connecting the conductive part and the gathering part are enhanced.

[0075] In some embodiments, the compaction rate of the compacted area is greater than or equal to 12%.

[0076] In the above technical solution, by setting the compaction rate of the compaction area to be greater than or equal to 12%, the gap in the compaction area can be further reduced, making the compaction area almost gapless. The part of the connector that enters the compaction area is less prone to thermal cracks and pores, thereby improving the overall flow capacity of the connector and the reliability and conductivity of the connector connecting the conductive part and the gathering part.

[0077] Secondly, embodiments of this application also provide a battery, including a battery cell of any of the above-described solutions.

[0078] In the above technical solution, the reliability of the battery cells is improved, which helps to improve the reliability of the battery.

[0079] Thirdly, embodiments of this application also provide an electrical device including a battery cell from any of the above-described solutions.

[0080] In the above technical solution, the improved reliability of the battery helps to improve the power consumption performance of the electrical device. Attached Figure Description

[0081] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0082] Figure 1 is a structural schematic diagram of a vehicle provided in some embodiments of this application;

[0083] Figure 2 is an exploded view of the battery structure provided in some embodiments of this application;

[0084] Figure 3 is a perspective view of a battery cell provided in some embodiments of this application;

[0085] Figure 4 is a top view of a battery cell provided in some embodiments of this application;

[0086] Figure 5 is a cross-sectional view along line DD in Figure 4;

[0087] Figure 6 is a magnified view of part B in Figure 5;

[0088] Figure 7 is a partial cross-sectional view of the welding of the electrode tab and the conductive part according to some embodiments of this application;

[0089] Figure 8 is a schematic diagram of ultrasonic pre-welding of the electrode tab by an ultrasonic welding device provided in some embodiments of this application;

[0090] Figure 9 is a magnified view of part C in Figure 8;

[0091] Figure 10 is a partial cross-sectional view of the welding of the electrode tab and the conductive part according to some embodiments of this application;

[0092] Figure 11 is a partial cross-sectional view of the welding of the electrode tab and the conductive part according to some embodiments of this application;

[0093] Figure 12 is a partial cross-sectional view of the welding of the electrode tab and the conductive part according to some embodiments of this application;

[0094] Figure 13 is a schematic diagram of the retractable portion provided in some embodiments of this application;

[0095] Figure 14 is a schematic diagram of the welding of the retractable part and the conductive part according to some embodiments of this application;

[0096] Figure 15 is a schematic diagram of the welding of the retractable part and the conductive part according to some embodiments of this application;

[0097] Figure 16 is a schematic diagram of a first face and a second face provided in some embodiments of this application;

[0098] Figure 17 is a schematic diagram of the first face shown in Figure 16;

[0099] Figure 18 is a schematic diagram of the second face shown in Figure 16;

[0100] Figure 19 is a schematic diagram of a first face and a second face provided in some embodiments of this application;

[0101] Figure 20 is a schematic diagram of the first face shown in Figure 19;

[0102] Figure 21 is a schematic diagram of the second face shown in Figure 19;

[0103] Figure 22 is a partial cross-sectional view of the converging part in Comparative Example 1;

[0104] Figure 23 is a partial cross-sectional view of the converging part and the conductive part after laser welding in Comparative Example 1.

[0105] Figure 24 is a partial cross-sectional view of the converging part in Comparative Example 2;

[0106] Figure 25 shows a partial cross-sectional view of the converging part and the conductive part after laser welding in Comparative Example 2.

[0107] Figure 26 is a partial cross-sectional view of the converging part in Comparative Example 3;

[0108] Figure 27 shows a partial cross-sectional view of the converging part and the conductive part after laser welding in Comparative Example 3.

[0109] Figure 28 is a partial cross-sectional view of the retractable part in Embodiment 1;

[0110] Figure 29 is a partial cross-sectional view of the retractable part and the conductive part after laser welding in Embodiment 1;

[0111] Figure 30 is a partial cross-sectional view of the retractable part in Embodiment 2;

[0112] Figure 31 is a partial cross-sectional view of the retractable part and the conductive part after laser welding in Embodiment 2;

[0113] Figure 32 is a partial cross-sectional view of the retractable part in Embodiment 3;

[0114] Figure 33 is a partial cross-sectional view of the retractable part and the conductive part after laser welding in Embodiment 3;

[0115] Figure 34 is a partial cross-sectional view of the retractable part in Embodiment 4;

[0116] Figure 35 is a partial cross-sectional view of the retractable part and the conductive part after laser welding in Example 4;

[0117] Figure 36 is a front view of an ultrasonic welding apparatus provided in some embodiments of this application;

[0118] Figure 37 is a left view of the ultrasonic welding device shown in Figure 36;

[0119] Figure 38 is a front view of a welding head provided in some embodiments of this application;

[0120] Figure 39 is a side view of a welding head provided in some embodiments of this application;

[0121] Figure 40 is a topographical diagram of the ultrasonic weld mark processed by the ultrasonic welding device shown in Figure 38.

[0122] Figure 41 is a topographic image of the ultrasonic weld mark and the conductive part after laser welding shown in Figure 40.

[0123] Figure 42 is a cross-sectional view along line AA in Figure 41;

[0124] Figure 43 is a partial enlarged view of part L in Figure 42;

[0125] Figure 44 is a partial enlarged view of part R in Figure 42;

[0126] Figure 45 is a side view of a welding head provided in some embodiments of this application;

[0127] Figure 46 is a topographical diagram of the ultrasonic weld mark processed by the ultrasonic welding device shown in Figure 45.

[0128] Figure 47 is a topographic image of the ultrasonic weld mark and the conductive part after laser welding shown in Figure 46.

[0129] Figure 48 is a partial cross-sectional topography of the laser weld shown in Figure 47;

[0130] Figure 49 is a side view of a welding head provided in some embodiments of this application;

[0131] Figure 50 is a topographical diagram of the ultrasonic weld mark processed by the ultrasonic welding device shown in Figure 49.

[0132] Figure 51 is a cross-sectional morphology diagram of the ultrasonic weld mark shown in Figure 50;

[0133] Figure 52 is a schematic diagram of the ultrasonic welding of the root pass weld shown in Figure 51;

[0134] Figure 53 is a cross-sectional view of the root weld shown in Figure 52;

[0135] Figure 54 is a schematic diagram of welding the main weld on the root pass weld shown in Figure 52;

[0136] Figure 55 is a cross-sectional view of the root weld and the main weld shown in Figure 54.

[0137] Reference numerals: Vehicle 1000; Battery 100; Controller 200; Motor 300; Housing 101; First Housing Body 1011; Second Housing Body 1012; Battery Cell 102; First Direction X; Second Direction Y; Third Direction Z; Fourth Direction E; Fifth Direction F; Housing Component 1; First Housing Wall 11; Receiving Cavity 12; Terminal Component 2; Conductive Part 20; Terminal Body 21; Electrode Assembly 3; Active Material Coating Part 31; Electrode Lug Part 32; Electrode Sheet 320; Closing Part 321; Compacted Region 3211; First Sub-region Z1; Protruding Section Z11; Second Sub-region Z2; Third Sub-region Z3; Region One Z31; Region Two Z32; First Compacted Row Z4; Fourth Sub-region Z5; Fifth Sub-region Z6; Second Compacted Row Z7; Fluffy Region 3212; First Fluffy Area L1; Second Fluffy Area L2; Third fluffy zone L3; Fourth fluffy zone L4; Fifth fluffy zone L5; Sixth fluffy zone L6; Connecting part 4; First part 41; Surface part 411; Outline of surface part 4x; Long side of surface part 4x1; Short side of surface part 4x2; Internal part 412; Outline of internal part 4y; Second part 42; First connecting part 4a; First face part 4a1; Second connecting part 4b; Second face part 4b1; Third connecting part 4c; Third face part 4c1; Ultrasonic welding device 2000; Welding head 400; Welding end 401; Welding tooth 5; Tooth part 51; First tooth part 514; Protrusion 5141; Second tooth part 515; Third tooth part 516; First sub-tooth 5161; Second sub-tooth 5162; Fourth tooth part 513; Fifth tooth part 517; Tooth groove 6; First straight groove 61; Second straight groove 62; 500mm welding base; 600mm drive cylinder. Detailed Implementation

[0138] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0139] Unless otherwise defined, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used in the description of this application is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms "comprising" and "having," and any variations thereof, in the description, claims, and accompanying drawings of this application are intended to cover non-exclusive inclusion. The terms "first," "second," etc., in the description, claims, or accompanying drawings of this application are used to distinguish different objects, not to describe a specific order or hierarchy.

[0140] In this application, the reference to "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment that is mutually exclusive with other embodiments.

[0141] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," "linking," and "attachment" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0142] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0143] In the embodiments of this application, the same reference numerals denote the same components, and for the sake of brevity, detailed descriptions of the same components are omitted in different embodiments. It should be understood that the thickness, length, width, and other dimensions of various components in the embodiments of this application shown in the accompanying drawings, as well as the overall thickness, length, width, and other dimensions of the integrated device, are merely illustrative and should not constitute any limitation on this application.

[0144] In this application, "multiple" means two or more (including two).

[0145] In this application, the battery cell may include lithium-ion secondary batteries, lithium-ion primary batteries, lithium-sulfur batteries, sodium-lithium-ion batteries, sodium-ion batteries, or magnesium-ion batteries, etc., and the embodiments of this application are not limited to these. The battery cell may be cylindrical, flat, cuboid, or other shapes, etc., and the embodiments of this application are not limited to these. Battery cells are generally divided into three types according to their packaging method: cylindrical battery cells, square battery cells, and pouch battery cells, and the embodiments of this application are not limited to these.

[0146] The battery mentioned in the embodiments of this application refers to a single physical module comprising one or more battery cells to provide higher voltage and capacity. For example, the battery mentioned in this application may include a battery module or a battery pack. A battery module generally includes multiple battery cells. A battery pack generally includes a housing for encapsulating one or more battery cells or one or more battery modules. The housing can prevent liquids or other foreign matter from affecting the charging or discharging of the battery cells.

[0147] A single battery cell includes a casing, electrode assemblies, and electrolyte. The casing houses the electrode assemblies and electrolyte. The casing contains at least one electrode assembly, which consists of a positive electrode, a negative electrode, and a separator. The electrode assembly can be a wound structure or a stacked structure, etc. The battery cell primarily functions by the movement of metal ions between the positive and negative electrode assemblies.

[0148] A positive electrode typically includes a positive current collector and a positive active material layer. The positive active material layer is directly or indirectly coated onto the positive current collector. The positive current collector without a positive active material layer protrudes from the one with a positive active material layer, serving as the positive electrode tab. Taking a lithium-ion battery as an example, the material of the positive current collector can be aluminum, and the material of the positive active material layer can be lithium cobalt oxide, lithium iron phosphate, ternary lithium, or lithium manganese oxide, etc.

[0149] A negative electrode typically includes a negative current collector and a negative active material layer. The negative active material layer is directly or indirectly coated onto the negative current collector. The negative current collector without a negative active material layer protrudes from the negative current collector with a negative active material layer, and the negative current collector without a negative active material layer serves as the negative electrode tab. The material of the negative current collector can be copper, and the material of the negative active material layer can be carbon or silicon, etc.

[0150] To ensure that a large current can be passed without melting, multiple positive electrode tabs are stacked together to form the positive electrode tab portion, and multiple negative electrode tabs are stacked together to form the negative electrode tab portion. A terminal component is provided on the housing component; the positive electrode tab portion is electrically connected to the positive electrode terminal component, and the negative electrode tab portion is electrically connected to the negative electrode terminal component.

[0151] In the production of battery cells, ultrasonic welding can be used to pre-weld multiple tabs in the tab area to form an ultrasonic weld mark. Then, laser welding is used to weld the ultrasonic weld mark to the conductive part of the terminal component, realizing the connection and electrical conduction between the electrode assembly and the terminal component. However, the contour of the laser weld has the problem of thermal cracking, which affects the conductivity and connection strength between the tab and the conductive part, thus affecting the reliability of the battery cell.

[0152] To address this, embodiments of this application propose a battery cell in which multiple tabs are connected to form a converged portion. The converged portion is stacked and connected with a conductive portion to form a connecting portion. The converged portion includes a compacted region, the thickness of which is less than the stacked thickness of the multiple tabs in the tab portion. The connecting portion includes a first portion formed in the converged portion and a second portion formed in the conductive portion. At least a majority of the outline of the first portion is located within the compacted region. Therefore, since at least a majority of the outline of the portion of the connecting portion formed on the converged portion is located within the compacted region, the multiple tabs are tightly bonded together in the compacted region. This helps to improve the problem of thermal cracking in the outline of the connecting portion, improves the conductivity and connection strength between the tabs and the conductive portion, and enhances the current carrying capacity and reliability of the battery cell.

[0153] This application provides an electrical device that uses a battery as a power source. The electrical device can be, but is not limited to, mobile phones, tablets, laptops, electric toys, power tools, electric vehicles, electric cars, ships, spacecraft, etc. Electric toys can include stationary or mobile electric toys, such as game consoles, electric car toys, electric ship toys, and electric airplane toys, etc. Spacecraft can include airplanes, rockets, space shuttles, and spacecraft, etc.

[0154] For ease of explanation, the following embodiments will use a vehicle as an example of an electrical device according to an embodiment of this application.

[0155] Please refer to Figure 1, which is a structural schematic diagram of a vehicle 1000 provided in some embodiments of this application. The vehicle 1000 can be a gasoline-powered vehicle, a natural gas-powered vehicle, or a new energy vehicle. New energy vehicles can be pure electric vehicles, hybrid electric vehicles, or range-extended electric vehicles, etc. A battery 100 is disposed inside the vehicle 1000, and the battery 100 can be located at the bottom, front, or rear of the vehicle 1000. The battery 100 can be used to power the vehicle 1000; for example, the battery 100 can serve as the operating power source for the vehicle 1000. The vehicle 1000 may also include a controller 200 and a motor 300. The controller 200 is used to control the battery 100 to supply power to the motor 300, for example, to meet the power needs of the vehicle 1000 during startup, navigation, and driving.

[0156] In some embodiments of this application, the battery 100 can not only serve as the operating power source for the vehicle 1000, but also as the driving power source for the vehicle 1000, replacing or partially replacing fuel or natural gas to provide driving power for the vehicle 1000.

[0157] Please refer to Figure 2, which is an exploded view of the structure of a battery 100 provided in some embodiments of this application. The battery 100 includes a housing 101 and a plurality of battery cells 102, with the battery cells 102 housed within the housing 101. The housing 101 provides assembly space for the battery cells 102, and the housing 101 can adopt various structures. In some embodiments, the housing 101 may include a first housing body 1011 and a second housing body 1012, which overlap each other, and together define an assembly space for accommodating the battery cells 102. The second box body 1012 can be a hollow structure open at one end, and the first box body 1011 can be a plate-shaped cover structure. The first box body 1011 covers the open side of the second box body 1012, so that the first box body 1011 and the second box body 1012 together define the assembly space. Alternatively, the first box body 1011 and the second box body 1012 can both be hollow structures open on one side, with the open side of the first box body 1011 covering the open side of the second box body 1012. Of course, the box 101 formed by the first box body 1011 and the second box body 1012 can be of various shapes, such as a cylinder, a cuboid, etc.

[0158] In battery 100, multiple battery cells 102 can be connected in series, parallel, or in a hybrid configuration. A hybrid configuration means that multiple battery cells 102 are connected in both series and parallel configurations. Multiple battery cells 102 can be directly connected in series, parallel, or in a hybrid configuration, and then the entire assembly of the multiple battery cells 102 is housed within housing 101. Alternatively, battery 100 can also be composed of multiple battery cells 102 first connected in series, parallel, or in a hybrid configuration to form a battery module, and then multiple battery modules are connected in series, parallel, or in a hybrid configuration to form a whole, which is also housed within housing 101. Battery 100 may also include other structures; for example, battery 100 may also include a busbar component for electrically welding multiple battery cells 102.

[0159] Each battery cell 102 can be a secondary battery or a primary battery; it can also be a lithium-sulfur battery, a sodium-ion battery, or a magnesium-ion battery, but is not limited to these. The battery cell 102 can be cylindrical, flat, cuboid, etc. For example, referring to the embodiment shown in Figure 3, the length direction of the battery cell 102 is the first direction X, the width direction of the battery cell 102 is the second direction Y, and the height direction of the battery cell 102 is the third direction Z. The first direction X, the second direction Y, and the third direction Z are all perpendicular to each other.

[0160] Please refer to Figures 3-7. Figure 3 is a perspective view of a battery cell 102 provided in some embodiments of this application; Figure 4 is a top view of the battery cell 102 shown in Figure 3; Figure 5 is a cross-sectional view along line DD in Figure 4; Figure 6 is a partial enlarged view of part B in Figure 5; Figure 7 is a partial cross-sectional view of the connection between the conductive part 20 and the gathering part 321 provided in some embodiments of this application. In some embodiments of this application, the battery cell 102 includes: a housing component 1, a terminal component 2, and an electrode assembly 3. The terminal component 2 is disposed on the housing component 1 and includes a conductive part 20. The electrode assembly 3 is housed in the housing component 1 and includes a tab part 32. The tab part 32 includes a plurality of tab pieces 320 stacked together. The plurality of tab pieces 320 are connected to form a gathering part 321. The gathering part 321 is stacked with the conductive part 20 and connected to form a connecting part 4.

[0161] For example, referring to Figures 3-6, the housing component 1 may include a first housing wall 11, and the pole member 2 is disposed on the first housing wall 11. The structure of the housing component 1 is not limited. For example, the housing component 1 may include a housing body and a housing cover, the housing body defining a cavity closed at one end and open at the other, and the housing cover covering the open end of the housing body. The housing cover may serve as the first housing wall 11, or the wall surface of the housing body opposite to the housing cover may also serve as the first housing wall 11. As another example, the housing component 1 may include two half-shells joined together, each half-shell defining a cavity open toward the other half-shell, with the wall surface of one half-shell away from the other half-shell serving as the first housing wall 11.

[0162] Referring to Figures 5 and 6, the electrode post component 2 includes a conductive part 20, which is the portion of the electrode post component 2 used to connect with the electrode assembly 3. For example, the conductive part 20 can be the electrode post body 21. In this case, the folded portion 321 formed by connecting the tabs 320 in the electrode assembly 3 is directly electrically connected to the electrode post body 21. Alternatively, the conductive part 20 can also be an adapter piece connected to the electrode post body 21. In this case, the folded portion 321 formed by connecting the tabs 320 in the electrode assembly 3 is directly electrically connected to the adapter piece, and the adapter piece is electrically connected to the electrode post body 21. Thus, the folded portion 321 is indirectly electrically connected to the electrode post body 21 through the adapter piece. For simplicity, the following description will mainly use the electrode post body 21 as an example for the conductive part 20.

[0163] Referring to Figures 5 and 6, the electrode assembly 3 includes an active material coating portion 31 housed within the housing component 1, and an electrode tab portion 32 connected to the active material coating portion 31. Exemplarily, a receiving cavity 12 is formed inside the housing component 1, the active material coating portion 31 is housed within the receiving cavity 12, the electrode post body 21 passes through the first housing wall 11, and the electrode tab portion 32 is welded to the electrode post body 21. The electrode tab portion 32 and the electrode post body 21 are directly electrically connected, such that the electrode tab portion 32 is electrically connected between the active material coating portion 31 and the electrode post body 21.

[0164] Referring to Figures 6 and 7, multiple tabs 320 in the tab portion 32 are stacked. These tabs 320 are connected to form a convergence portion 321. That is, the portion where multiple tabs 320 are connected together through a connecting process constitutes the convergence portion 321. Therefore, the multiple tabs 320 in the convergence portion 321 not only exhibit a stacked arrangement but also a connected relationship. The thicker side of the convergence portion 321 faces the conductive portion 20 and is disposed on the conductive portion 20 to achieve the stacking of the convergence portion 321 and the conductive portion 20. The convergence portion 321 and the conductive portion 20 are connected together through a connecting process, and the connected portion forms the connecting portion 4.

[0165] The connection method of the multiple tabs 320 in the gathering part 321 is not limited, such as welding, drilling, or bonding. The connection method between the gathering part 321 and the conductive part 20 is also not limited, such as welding, drilling, or bonding. For the sake of simplicity, the following description mainly uses ultrasonic welding of the multiple tabs 320 in the gathering part 321 and laser welding of the gathering part 321 and the conductive part 20 as examples. The gathering part 321 is ultrasonically welded, and the connecting part 4 is laser welded.

[0166] In the embodiments of this application, referring to Figures 7-9, the gathering portion 321 includes a compacted region 3211, the thickness T1 of which is less than the theoretical thickness T2 of the tab portion 32. Since the thickness T1 of the compacted region 3211 is less than the theoretical thickness T2 of the tab portion 32, it indicates that the tabs 320 in the compacted region 3211 are compressed, yielded, and undergo plastic deformation. This reduces the thickness of the tabs 320, resulting in the multiple tabs 320 in the compacted region 3211 being tightly bonded together with little or no interlayer gaps. The compaction rate of the compacted region 3211 is greater than 0%.

[0167] The "compaction rate" of the gathering portion 321 refers to the ratio of the difference between the theoretical thickness T2 of the tab portion 32 and the thickness T1 of the compacted region 3211 to the theoretical thickness T2 of the tab portion 32, i.e., (T2-T1) / T2. The theoretical thickness T2 refers to the stacking thickness of multiple tabs 320 in the tab portion 32, i.e., the thickness of the tabs 320 without compression and stacked together in multiple layers without gaps. For example, if the thickness of a single tab 320 is a (i.e., a is the thickness of a single layer of foil), and b layers of tabs 320 are stacked in the tab portion 32 (i.e., b is the number of layers of foil), then the stacking thickness of multiple layers of tabs 320 in the tab portion 32 is a×b. Therefore, the theoretical thickness T2 of the tab portion 32 is a×b.

[0168] For example, referring to Figures 8 and 9, the gathering part 321 is processed by ultrasonic welding. The welding head 400 used in the ultrasonic welding process has welding teeth 5 and tooth grooves 6. The welding teeth 5 are divided into multiple tooth parts 51 spaced apart by the tooth grooves 6. That is, the tooth grooves 6 are the inter-tooth gaps between the multiple tooth parts 51 of the welding teeth 5. After welding, the area on the gathering part 321 corresponding to the tooth parts 51 is the compacted area 3211, and the area on the gathering part 321 corresponding to the tooth grooves 6 is the fluffy area 3212. The multi-layer tabs 320 in the compacted area 3211 are effectively welded together, and there are no or almost no interlayer gaps between the foils. The multi-layer tabs 320 in the fluffy area 3212 are not effectively fused together, and there are interlayer gaps between the multi-layer tabs 320.

[0169] In the embodiments of this application, referring again to Figures 6 and 7, the connecting portion 4 includes a first portion 41 formed on the gathering portion 321 and a second portion 42 formed on the conductive portion 20. It can be understood that the connecting portion 4 needs to connect the conductive portion 20 and the gathering portion 321. Therefore, a portion of the connecting portion 4 is formed on the gathering portion 321, which is the first portion 41, and the remaining portion is formed on the conductive portion 20, which is the second portion 42.

[0170] For example, referring to FIG7, when laser welding is performed from the side of the gathering portion 321 away from the conductive portion 20, the first portion 41 of the connecting portion 4 formed on the gathering portion 321 may include: a surface portion 411 formed on the outer surface of the gathering portion 321, and an inner portion 412 formed within the gathering portion 321. In this case, the outline 4x of the surface portion 411 and the outline 4y of the inner portion 412 constitute the outline of the first portion 41. Alternatively, if laser welding is performed from the side of the conductive portion 20 away from the gathering portion 321, the first portion 41 of the connecting portion 4 formed on the gathering portion 321 may only include: the inner portion 412 formed within the gathering portion 321. In this case, the outline 4y of the inner portion 412 constitutes the outline of the first portion 41.

[0171] At least a majority of the outline of the first part 41 is located in the compacted region 3211, that is, at least a majority of the outline of the portion of the connecting part 4 formed on the gathering part 321 is located within the compacted region 3211. Since at least a majority of the outline of the portion of the connecting part 4 formed on the gathering part 321 is located within the compacted region 3211, this means that at least 50% (including 50%) of the outline of the portion of the connecting part 4 formed on the gathering part 321 is located within the compacted region 3211. For example, the entire outline of the portion of the connecting part 4 formed on the gathering part 321 may be located within the compacted region 3211; or, for another example, a portion of the outline of the portion of the connecting part 4 formed on the gathering part 321 may fall within the compacted region 3211, while the remaining portion of the outline falls within the fluffy region 3212, with the proportion of the outline falling within the compacted region 3211 being greater than the proportion falling within the fluffy region 3212.

[0172] Thus, in the above technical solution, since at least most of the outline of the portion of the connecting part 4 formed on the gathering part 321 is set in the compaction region 3211, the multilayer tabs 320 in the compaction region 3211 are very tightly bonded together with no or almost no interlayer gaps. This can improve the problem of hot cracks appearing in the weld outline due to interlayer gaps, thereby improving the conductivity yield and connection strength of the tab 32 and the conductive part 20, and improving the reliability of the battery cell 102.

[0173] In some embodiments of this application, referring to FIG7, the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20. The first portion 41 includes a surface portion 411 formed on the outer surface of the closing portion 321 and an inner portion 412 formed within the closing portion 321. Herein, "outer surface of the closing portion 321" refers to the side of the closing portion 321 away from the conductive portion 20.

[0174] For example, when the connecting part 4 is obtained by laser welding, laser welding can be performed from the side of the closing part 321 away from the conductive part 20. The connecting part 4 is a laser weld. The molten pool of the laser weld extends from the closing part 321 to the conductive part 20, and the molten pool can generally present a shape that extends along the thickness direction of the closing part 321 and gradually shrinks. The part of the laser weld on the surface of the closing part 321 is the surface part 411 of the first part 41, the part of the molten pool inside the closing part 321 is the internal part 412 of the first part 41, and the part of the molten pool inside the conductive part 20 is the second part 42.

[0175] Therefore, by setting the extension direction of the connecting part 4 to be from the closing part 321 to the conductive part 20, it is convenient for the welding head 400 to be aligned with the closing part 321. The welding head 400 can reasonably design the welding trajectory according to the distribution of the compacted area 3211 and the fluffy area 3212 on the closing part 321, and accurately weld along the welding trajectory, so that at least most of the outline of the part of the connecting part 4 formed on the closing part 321 can be reliably located in the compacted area 3211, thereby effectively improving the conductivity and connection strength of the tab part 32 and the conductive part 20, and improving the overcurrent capacity and reliability of the battery cell 102.

[0176] In the embodiments of this application, when the connecting part 4 is a laser weld, it may include only one weld, completed in one welding operation, or it may include multiple overlapping welds, completed in multiple welding operations. In this case, the total weld formed by the fusion of the multiple welds constitutes the connecting part 4. For example, referring to FIG10, the laser weld may include a root weld (e.g., the first connecting part 4a marked in FIG10), a main weld (e.g., the second connecting part 4b marked in FIG10), and a repair weld (e.g., the third connecting part 4c marked in FIG10) welded sequentially. In this case, the total weld formed by the fusion of the three welds constitutes the connecting part 4. As another example, referring to FIG11, the repair weld may be omitted, and the root weld (e.g., the first connecting part 4a marked in FIG11) and the main weld (e.g., the second connecting part 4b marked in FIG11) may be welded sequentially. In this case, the total weld formed by the fusion of these two welds constitutes the connecting part 4. For example, referring to Figure 7, the repair weld and the root weld can be omitted, and only one main weld (e.g., the second connection part 4b marked in Figure 7) can be welded, which constitutes the connection part 4.

[0177] In some embodiments, referring to Figures 10 and 12, when the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20, at least a majority of the area of ​​the surface portion 411 (e.g., the area of ​​the shaded region shown in Figure 12) can be disposed in the compaction region 3211, that is, at least 50% (including 50%) of the area of ​​the surface portion 411 can be disposed in the compaction region 3211. Thus, since the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20, the inner portion 412 can extend from the surface portion 411 toward the conductive portion 20. When at least a majority of the area of ​​the surface portion 411 falls within the compaction region 3211, it is advantageous to increase the volume of the inner portion 412 within the compaction region 3211. Since there are no or almost no interlayer gaps between the multilayer tabs 320 within the compaction region 3211, pores caused by interlayer gaps are less likely to appear in the molten pool of the compaction region 3211, thereby reducing the pores formed in the inner portion 412 and improving the flow capacity of the connecting portion 4.

[0178] In some embodiments of this application, referring to Figures 7 and 12, at least a majority of the outline 4x of the surface portion 411 (e.g., the outline of the shaded area shown in Figure 12, such as the rectangular frame enclosed by the two long sides 4x1 and the two short sides 4x2) falls within the compacted region 3211. That is, more than 50% (including 50%) of the outline 4x of the surface portion 411 falls within the compacted region 3211. Therefore, by ensuring that at least a majority of the outline 4x of the surface portion 411 falls within the compacted region 3211, the problem of hot cracking in the weld outline of the connecting portion 4 on the surface of the retracted portion 321 can be effectively improved. Furthermore, since the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20, the outline 4y of the inner portion 412 can extend from the outline 4x of the surface portion 411 toward the conductive portion 20. When at least most of the outline 4x of the surface portion 411 falls in the compacted region 3211, it is beneficial to increase the proportion of the outline 4y of the inner portion 412 falling in the compacted region 3211 relative to falling in the fluffy region 3212. This is beneficial to improve the problem of thermal cracking of the outline of the first portion 41 of the connecting portion 4 formed in the closing portion 321 as a whole.

[0179] In some embodiments of this application, referring to Figures 7 and 12, when more than 60% of the outline 4x of the surface portion 411 falls within the compacted region 3211, the problem of hot cracking in the weld outline of the connecting portion 4 on the surface of the closing portion 321 can be further improved. Furthermore, since the connecting portion 4 extends from the outer surface of the closing portion 321 towards the conductive portion 20, the outline 4y of the inner portion 412 can extend from the outline 4x of the surface portion 411 towards the conductive portion 20. When more than 60% of the outline 4x of the surface portion 411 falls within the compacted region 3211, it is beneficial to further increase the proportion of the outline 4y of the inner portion 412 falling within the compacted region 3211 relative to falling within the loose region 3212, thereby further improving the overall problem of hot cracking in the outline of the first portion 41 of the connecting portion 4 formed on the closing portion 321.

[0180] In some embodiments of this application, referring to FIG12, the surface of the gathering portion 321 is elongated, and the surface portion 411 is elongated and matches the length direction of the gathering portion 321, that is, the length direction of the surface portion 411 is consistent with the length direction of the gathering portion 321. For example, the fourth direction E shown in FIG12 is the length direction of the gathering portion 321. At least most of each of the two long sides 4x1 of the surface portion 411 is located in the compacted region 3211, that is, more than 50% (including 50%) of the length of each long side 4x1 is located in the compacted region 3211.

[0181] Therefore, the surface portion 411 can make full use of the space of the convergence portion 321, increase the area of ​​the surface portion 411, improve the current carrying capacity, and by setting at least most of each long side 4x1 to be located in the compaction region 3211, it is beneficial to increase the portion of the outline 4x of the surface portion 411 that falls in the compaction region 3211, improve the problem of thermal cracking of the outline of the surface portion 411, improve the conductivity yield and connection strength between the convergence portion 321 and the conductive portion 20, and thus improve the reliability of the battery cell 102.

[0182] In some embodiments, referring to Figures 12 and 13, the compaction region 3211 includes a first sub-region Z1. The first sub-region Z1 is elongated and matches the length and width directions of the converging portion 321, respectively. That is, the length direction of the first sub-region Z1 is consistent with the length direction of the converging portion 321, for example, the fourth direction E shown in Figure 13 is the length direction of the converging portion 321. The width direction of the first sub-region Z1 is consistent with the width direction of the converging portion 321, for example, the fifth direction F shown in Figure 13 is the width direction of the converging portion 321. The length M1 of the first sub-region Z1 exceeds half the length M of the converging portion 321, that is, the ratio of the length M1 of the first sub-region Z1 to the length M of the converging portion 321 is greater than 50%. There are two first sub-regions Z1, which are spaced apart along the width direction of the converging portion 321. The two long sides 4x1 of the surface portion 411 are respectively located in two first sub-regions Z1, that is, one long side 4x1 is located in one of the first sub-regions Z1, and the other long side 4x1 is located in the other first sub-region Z1.

[0183] Therefore, by setting the compaction region 3211 to include the two first sub-regions Z1, and setting the two long sides (4x1) of the surface portion 411 of the connecting portion 4 to the two first sub-regions Z1 respectively, the length of the first sub-regions Z1 is larger, and most of the contour of the surface portion 411 can fully utilize the compaction region 3211. This further increases the portion of the contour line 4x of the surface portion 411 falling within the compaction region 3211, thereby further improving the problem of thermal cracking in the contour of the surface portion 411, further improving the conductivity and connection strength between the convergence portion 321 and the conductive portion 20, and thus improving the reliability of the battery cell 102. Moreover, when the internal portion 412 extends from the surface portion 411 toward the conductive portion 20, most of the internal portion 412 can also fall into the first sub-region Z1, which helps to increase the volume of the internal portion 412 falling within the compaction region 3211, further improving the problem of pores in the internal portion 412, and thus further improving the current carrying capacity.

[0184] For example, the width M2 of the first sub-region Z1 (the minimum width of the first sub-region Z1) exceeds one-fifth of the width M of the converging portion 321. Therefore, the first sub-region Z1 has a relatively large area proportion relative to the converging portion 321, which is beneficial for fully utilizing the area of ​​the converging portion 321 and performing laser welding with the conductive portion 20. This allows the contour of the laser weld to fall more within the compacted area 3211, thereby improving the conductivity and connection strength between the converging portion 321 and the conductive portion 20.

[0185] In some embodiments, referring to FIG13, each long side of the first sub-region Z1 has a plurality of protruding segments Z11 spaced apart along the length direction of the converging portion 321, the protruding segments Z11 protruding toward the width direction of the converging portion 321. That is, each long side of the first sub-region Z1 away from another first sub-region Z1 has a plurality of protruding segments Z11 protruding toward the direction away from the other first sub-region Z1, and the protruding segments Z11 on this long side are spaced apart along the length direction of the long side. At the same time, each long side of the first sub-region Z1 close to another first sub-region Z1 has a plurality of protruding segments Z11 protruding toward the other first sub-region Z1, and the protruding segments Z11 on this long side are spaced apart along the length direction of the long side.

[0186] Therefore, each long side of the first sub-region Z1 is uneven, which helps to improve the grip during welding and provide greater friction, so that the first sub-region Z1 can be effectively compacted and the compaction rate of the first sub-region Z1 can be improved. In this way, when part of the laser weld contour falls on the first sub-region Z1, the problem of hot cracking in that part of the contour can be further improved.

[0187] In some embodiments, referring to FIG13, the compaction region 3211 includes a plurality of second sub-regions Z2 disposed between two first sub-regions Z1 and spaced apart along the length direction of the converging portion 321. That is, the compaction region 3211 includes a plurality of second sub-regions Z2 spaced apart along the length direction of the converging portion 321, and in the width direction of the converging portion 321, the plurality of second sub-regions Z2 are located between two first sub-regions Z1. Referring to FIG13, the protruding segments Z11 on the side of the two first sub-regions Z1 that are close to each other are positioned opposite each other, and two opposing protruding segments Z11 are respectively disposed between each pair of adjacent second sub-regions Z2. That is, the non-protruding positions on the side of the two first sub-regions Z1 that are close to each other are also opposite each other. The second sub-regions Z2 are disposed in opposing and non-protruding positions so that the plurality of second sub-regions Z2 and the plurality of protruding segments Z11 are alternately disposed along the length direction of the converging portion 321.

[0188] Therefore, the space of the gathering part 321 can be further utilized to construct the compaction area 3211. When the two long sides 4x1 of the surface part 411 are respectively located in the two first sub-regions Z1, the surface part 411 can cover at least part of the second sub-region Z2, which is conducive to increasing the portion of the laser weld falling in the compaction area 3211, further improving the problem of porosity in the molten pool of the laser weld, and further improving the flow capacity.

[0189] In some embodiments, referring to FIG13, the gathering portion 321 includes a fluffy region 3212. The fluffy region 3212 includes a first fluffy area L1 disposed between two first sub-regions Z1 and separated between the two first sub-regions Z1 and between the first sub-region Z1 and the second sub-region Z2. The first fluffy area L1 presents a line form on the outer surface of the gathering portion 321 so that the outline of the second sub-region Z2 matches the outline of the first sub-region Z1.

[0190] In the above technical solution, by setting a first fluffy area L1 in the form of lines to separate two first sub-regions Z1, and separating the first sub-region Z1 and the second sub-region Z2, the outline of the second sub-region Z2 matches the outline of the two first sub-regions Z1. That is, the protruding position of the outline of the first sub-region Z1 corresponds to the concave position of the outline of the second sub-region Z2. The distance between the two first sub-regions Z1 is small, and the distance between the first sub-region Z1 and the second sub-region Z2 is small, so that most of the area where the molten pool of the laser weld is located is a compacted area 3211, which helps to improve the problem of porosity in the molten pool of the laser weld and further improves the flow capacity.

[0191] For example, on the outer surface of the converging part 321, the width of the first fluffy area L1 in the form of lines can be only 0.2mm-0.6mm, so that the distance between the two first sub-regions Z1 is small, and the distance between the first sub-region Z1 and the second sub-region Z2 is small. This is beneficial because most of the area where the molten pool of the laser weld is located is a compacted area 3211, which helps to improve the problem of porosity in the molten pool of the laser weld and further improves the flow capacity.

[0192] In some embodiments, referring to FIG13, the compaction region 3211 includes a plurality of third sub-regions Z3, which are arranged in a spaced-apart manner around two first sub-regions Z1. That is, each first sub-region Z1 has a third sub-region Z3 on both sides of the length direction of the converging portion 321, and each first sub-region Z1 also has a third sub-region Z3 on the side of the width direction of the converging portion 321 away from the other first sub-region Z1.

[0193] Therefore, by setting multiple third sub-regions Z3 around the two first sub-regions Z1, it helps to improve the gripping force during welding, thereby providing greater friction and enabling the first sub-regions Z1 to be effectively compacted, thus improving the compaction rate of the first sub-regions Z1. In this way, when part of the laser weld contour falls on the first sub-region Z1, the problem of hot cracking in that part of the contour can be further improved.

[0194] In some embodiments, referring to FIG13, the gathering portion 321 includes a fluffy region 3212. The fluffy region 3212 includes a second fluffy region L2 disposed on the outer periphery of two first sub-regions Z1 and separated between the first sub-regions Z1 and the third sub-regions Z3 and between two adjacent third sub-regions Z3. The second fluffy region L2 presents a line form on the outer surface of the gathering portion 321 so that the outline of the third sub-regions Z3 matches the outline of the first sub-regions Z1.

[0195] For example, the long side of the first sub-region Z1 is concave-convex. The multiple third sub-regions Z3 located on the long side of the first sub-region Z1 can be divided into region one Z31 and region two Z32, which are alternately arranged along the length direction of the converging part 321. Region one Z31 has a relatively large area and is opposite to the non-protruding position of the long side of the first sub-region Z1. Region two Z32 has a relatively small area and is opposite to the protruding segment Z11 of the long side of the first sub-region Z1. Thus, the outline of the third sub-region Z3 can be matched with the outline of the first sub-region Z1.

[0196] In the above technical solution, by setting a second fluffy area L2 in the form of lines to separate the first sub-region Z1 and the third sub-region Z3, and to separate adjacent third sub-region Z3, the outline of the third sub-region Z3 matches the outline of the first sub-region Z1. That is, the protruding position of the outline of the first sub-region Z1 corresponds to the concave position of the outline of the third sub-region Z3. The spacing between adjacent third sub-regions Z3 is small, and the spacing between the first sub-region Z1 and the third sub-region Z3 is small. This allows for more full utilization of the space of the converging part 321 to construct the compaction area 3211, thereby improving the gripping force during welding, providing greater friction, and increasing the compaction rate of the first sub-region Z1. In this way, when part of the outline of the laser weld falls on the first sub-region Z1, the problem of hot cracking in that part of the outline can be further improved.

[0197] For example, on the outer surface of the gathering part 321, the width of the second fluffy area L2 in the form of lines can be only 0.2mm-0.6mm, so that the spacing between adjacent third sub-regions Z3 is small, and the spacing between the first sub-region Z1 and the third sub-region Z3 is small, which is conducive to improving the gripping force during welding, so as to provide greater friction and further improve the compaction rate of the first sub-region Z1.

[0198] In some other embodiments of this application, referring to FIG14, the compaction region 3211 includes a plurality of first compaction rows Z4 spaced apart along the width direction of the gathering portion 321 (e.g., the fifth direction F shown in FIG14). Each first compaction row Z4 includes a plurality of fourth sub-regions Z5 spaced apart along the length direction of the gathering portion 321 (e.g., the fourth direction E shown in FIG14). Two long sides 4x1 of the surface portion 411 are respectively corresponding to two of the first compaction rows Z4, and each long side 4x1 passes through a plurality of fourth sub-regions Z5 in the corresponding first compaction row Z4. The dimension M2 of the fourth sub-region Z5 in the length direction of the gathering portion 321 is greater than the distance M3 between two adjacent fourth sub-regions Z5 in the length direction of the gathering portion 321.

[0199] For example, referring to FIG14, the gathering portion 321 includes a fluffy region 3212, the fluffy region 3212 including a third fluffy region L3 separating two adjacent fourth sub-regions Z5 in the same first compacted row Z4, the third fluffy region L3 presents a line form extending along the width direction of the gathering portion 321 (e.g., the fifth direction F shown in FIG14) on the outer surface of the gathering portion 321, and the dimension M2 of the fourth sub-region Z5 in the length direction of the gathering portion 321 (e.g., the fourth direction E shown in FIG14) is greater than the width M3 of the fourth fluffy region L4 in the length direction of the gathering portion 321 (e.g., the fourth direction E shown in FIG14).

[0200] Therefore, by setting the compacted region 3211 to include multiple fourth sub-regions Z5 arranged as described above, and setting the dimension M2 of the fourth sub-region Z5 in the length direction of the converging portion 321 to be greater than the distance M3 between two adjacent fourth sub-regions Z5 in the length direction of the converging portion 321, and by setting the two long sides 4x1 of the surface portion 411 of the connecting portion 4 to correspond to the two first compacted rows Z4 respectively, and each long side 4x1 passes through multiple fourth sub-regions Z5 in the corresponding first compacted row Z4, most of the contour of the surface portion 411 can fully utilize the compacted region 3211, thereby increasing the portion of the contour line 4x of the surface portion 411 falling on the compacted region 3211, improving the problem of thermal cracking in the contour of the surface portion 411, improving the conductivity yield and connection strength between the converging portion 321 and the conductive portion 20, and thus improving the reliability of the battery cell 102. Furthermore, when the internal portion 412 extends from the surface portion 411 toward the conductive portion 20, most of the internal portion 412 can also fall into the fourth sub-region Z5, which helps to increase the volume of the internal portion 412 falling into the compaction region 3211, thereby further improving the problem of pores in the internal portion 412 and further improving the flow capacity.

[0201] For example, referring to FIG14, there are two first compacted rows Z4, the fourth sub-region Z5 is elongated, and the length direction of the fourth sub-region Z5 (e.g., the fifth direction F shown in FIG14) matches the width direction of the converging part 321, the width direction of the fourth sub-region Z5 (e.g., the fourth direction E shown in FIG14) matches the length direction of the converging part 321, and the length N2 of the fourth sub-region Z5 exceeds one-quarter of the width N of the converging part 321.

[0202] Therefore, the fourth sub-region Z5 can make full use of the space of the gathering part 321, and the area of ​​the fourth sub-region Z5 is relatively large. When the outline of the laser weld passes through multiple fourth sub-regions Z5, it is beneficial to improve the problem of hot cracking in the outline of the laser weld and improve the problem of porosity in the molten pool of the laser weld, thereby improving the conductivity and connection strength of the gathering part 321 and the conductive part 20.

[0203] For example, referring to FIG14, the gathering portion 321 includes a fluffy region 3212, the fluffy region 3212 including a third fluffy region L3 separated between two adjacent fourth sub-regions Z5 in the same first compacted row Z4, and a fourth fluffy region L4 separated between two adjacent first compacted rows Z4. The third fluffy region L3 is in the form of a line extending along the width direction of the gathering portion 321 on the outer surface of the gathering portion 321, and the fourth fluffy region L4 is in the form of a line extending along the length direction of the gathering portion 321 on the outer surface of the gathering portion 321. The width M3 of the third fluffy region L3 is smaller than the width M4 of the fourth fluffy region L4.

[0204] This helps reduce the length of the long side 4x1 of the surface portion 411 falling within the third fluffing zone L3, further improving the problem of hot cracking in the contour of the surface portion 411. Furthermore, since both the third fluffing zone L3 and the fourth fluffing zone L4 are linear on the outer surface of the converging portion 321, it helps increase the proportion of the fourth sub-region Z5 relative to the converging portion 321, i.e., it helps increase the proportion of the compacted region 3211 relative to the converging portion 321. Thus, when the contour line of the laser weld passes through multiple fourth sub-regions Z5, it can improve the problem of hot cracking in the contour line of the laser weld and further improve the problem of porosity in the molten pool of the laser weld, thereby improving the flow capacity.

[0205] For example, the shape of the fourth sub-region Z5 is not limited. For example, it can be a rectangle, a circle, etc. When it is processed into a rectangle, it is convenient for the design of the welding head 400 and it is beneficial to increase the proportion of the compaction area 3211, so that the surface portion 411 falls more into the fourth sub-region Z5.

[0206] In some embodiments, referring to FIG15, the entire surface portion 411 is located within the compacted region 3211. That is, the surface portion 411 falls entirely within the compacted region 3211, without any portion falling within the fluffy region 3212, so that the entire outline of the surface portion 411 can be located within the compacted region 3211.

[0207] Therefore, the entire contour of the surface portion 411 is less prone to thermal cracking, effectively improving the conductivity and connection strength between the converged portion 321 and the conductive portion 20, and enhancing the reliability of the battery cell 102. Furthermore, since the connecting portion 4 extends from the outer surface of the converged portion 321 towards the conductive portion 20, when the surface portion 411 is entirely located in the compacted region 3211, if the internal portion 412 has a shape that extends and gradually decreases along the thickness direction of the converged portion 321 from the surface portion 411 to the conductive portion 20, then the internal portion 412 can also fall entirely within the compacted region 3211. This further reduces the likelihood of thermal cracking in the contour of the internal portion 412, further improving the conductivity and connection strength between the converged portion 321 and the conductive portion 20, and enhancing the reliability of the battery cell 102. Moreover, the internal portion 412 is less prone to pores, further improving current carrying capacity.

[0208] In some embodiments, referring to FIG15, the compaction region 3211 includes a plurality of fifth sub-regions Z6 spaced apart, and the surface portion 411 is a plurality of spaced-apart portions corresponding one-to-one with the plurality of fifth sub-regions Z6. For example, a pulsed laser can be used to weld at each fifth sub-region Z6, so that each fifth sub-region Z6 has a surface portion 411 of the connecting portion 4.

[0209] For example, when the tab 320 is aluminum foil, aluminum has a large coefficient of thermal expansion. The greater the heat input during laser welding, the more severe the thermal cracking of the aluminum tab will be. A pulsed laser with low heat input can be used for laser welding. The laser welding position falls on the compaction area 3211, which can improve the problem of thermal cracking in the contour of the laser weld.

[0210] Therefore, by setting the compaction region 3211 to include multiple fifth sub-regions Z6 spaced apart, and by setting multiple surface portions 411 to correspond one-to-one with multiple fifth sub-regions Z6, it is possible to simply and effectively realize that the entire surface portion 411 is located in the compaction region 3211. Moreover, the total area of ​​the surface portions 411 is relatively large, which meets the requirements of current carrying capacity. Furthermore, if the internal portion 412 has a shape that extends from the surface portion 411 to the conductive portion 20 along the thickness direction of the converging portion 321 and gradually decreases, the internal portions 412 extending from each surface portion 411 can also fall into the fifth sub-regions Z6 respectively. This makes it less likely for the outline of the internal portion 412 to have thermal cracks and less likely for the internal portion 412 to have pores. This is beneficial to improving the conductivity and connection strength between the converging portion 321 and the conductive portion 20, improving the current carrying capacity, and enhancing the reliability of the battery cell 102.

[0211] In some embodiments, referring to FIG15, the compaction region 3211 includes a plurality of second compaction rows Z7 spaced apart along the width direction of the gathering portion 321 (e.g., the fifth direction F shown in FIG15), and each second compaction row Z7 includes a plurality of fifth sub-regions Z6 spaced apart along the length direction of the gathering portion 321 (e.g., the fourth direction E shown in FIG15). Therefore, by configuring the compaction region 3211 as having a plurality of fifth sub-regions Z6 including the above-described arrangement, the arrangement of the fifth sub-regions Z6 can be simplified, making it easier to accurately locate each fifth sub-region Z6 for laser welding. Furthermore, it simplifies the design of the compaction region 3211, making the gathering portion 321 easier to process and reducing the design and processing difficulty of the welding head used to process the gathering portion 321.

[0212] For example, referring to FIG15, the gathering portion 321 includes a fluffy region 3212. The fluffy region 3212 includes a fifth fluffy area L5 separated between two adjacent fifth sub-regions Z6 in the same second compaction row Z7, and a sixth fluffy area L6 separated between two adjacent second compaction rows Z7. The fifth fluffy area L5 is in the form of a line extending along the width direction of the gathering portion 321 on the outer surface of the gathering portion 321, and the sixth fluffy area L6 is in the form of a line extending along the length direction of the gathering portion 321 on the outer surface of the gathering portion 321. The width M5 of the fifth fluffy area L5 is smaller than the dimension M6 of the fifth sub-region Z6 along the length direction of the gathering portion 321 (e.g., the fourth direction E shown in FIG15), and the width M7 of the sixth fluffy area L6 is smaller than the dimension N3 of the fifth sub-region Z6 along the width direction of the gathering portion 321 (e.g., the fifth direction F shown in FIG15). This is beneficial to increase the area of ​​each fifth sub-region Z6, thereby increasing the proportion of the compaction region 3211.

[0213] In some embodiments, referring to FIG15, there are two second compacted rows Z7, and the fifth sub-region Z6 has a dimension N3 in the width direction (e.g., the fifth direction F shown in FIG15) and a dimension M6 in the length direction (e.g., the fourth direction E shown in FIG15) of the gathering portion 321, both exceeding one-quarter of the width N of the gathering portion 321.

[0214] Therefore, by setting two second compaction rows Z7, and setting the fifth sub-region Z6 such that both the dimension N3 in the width direction of the gathering portion 321 and the dimension M6 in the length direction of the gathering portion 321 exceed one-quarter of the width N of the gathering portion 321, the area of ​​each fifth sub-region Z6 is relatively large, which is beneficial to reduce the number of fifth sub-regions Z6, reduce the number of welding operations, and make the area of ​​each surface portion 411 relatively large, which is convenient for processing and improves the flow capacity.

[0215] For example, the shape of the fifth sub-region Z6 is not limited. For example, it can be a rectangle, a circle, etc. When it is processed into a rectangle, it is convenient for the design of the welding head 400, which is conducive to increasing the area of ​​each fifth sub-region Z6, thereby increasing the proportion of the compaction region 3211.

[0216] In some embodiments of this application, referring to FIG10, the connecting portion 4 includes a first connecting portion 4a and a second connecting portion 4b, the second connecting portion 4b extending into the conductive portion 20, the extension depth G1 of the first connecting portion 4a being less than the extension depth G2 of the second connecting portion 4b, the surface portion 411 including a first face 4a1 formed by the first connecting portion 4a on the outer surface of the gathering portion 321, and a second face 4b1 formed by the second connecting portion 4b on the outer surface of the gathering portion 321, at least a majority of the outline of the second face 4b1 being located within the first face 4a1.

[0217] Since the connecting portion 4 extends from the outer surface of the gathering portion 321 toward the conductive portion 20, and the connecting portion 4 includes a first connecting portion 4a and a second connecting portion 4b, the first connecting portion 4a extends from the outer surface of the gathering portion 321 toward the conductive portion 20, and thus the first connecting portion 4a includes a first face 4a1 formed on the outer surface of the gathering portion 321. The second connecting portion 4b also extends from the outer surface of the gathering portion 321 toward the conductive portion 20, and thus the second connecting portion 4b includes a second face 4b1 formed on the outer surface of the gathering portion 321.

[0218] For example, referring to FIG11, the connecting portion 4 includes only a first connecting portion 4a and a second connecting portion 4b, so that the connecting portion 4 is composed of the first connecting portion 4a and the second connecting portion 4b, and the surface portion 411 is composed of a first face 4a1 and a second face 4b1. However, this application is not limited to this, and the connecting portion 4 may also include other portions besides the first connecting portion 4a and the second connecting portion 4b. For example, referring to FIG10, it may also include a third connecting portion 4c.

[0219] When the connecting portion 4 extends along the thickness direction of the retracting portion 321, the extension depth is the depth in the thickness direction of the retracting portion 321 (for example, the third direction Z shown in FIG. 10). If it extends along an angle inclined to the thickness direction of the retracting portion 321, the extension depth is the depth along that angled direction. For the sake of simplicity, the following description will use the extension depth in the thickness direction of the retracting portion 321 as an example.

[0220] In the above technical solution, since the extension depth G2 of the second connecting portion 4b is relatively larger than the extension depth G1 of the first connecting portion 4a, the second connecting portion 4b can extend into the conductive portion 20. Thus, a portion of the second connecting portion 4b is formed in the closing portion 321, and the remaining portion is formed within the conductive portion 20. The second connecting portion 4b can serve to connect the closing portion 321 and the conductive portion 20. Furthermore, since the extension depth G1 of the first connecting portion 4a is smaller than the extension depth G2 of the second connecting portion 4b, the energy required for the first connecting portion 4a during laser welding is smaller, and the contour of the first connecting portion 4a is less prone to thermal cracking. Furthermore, since at least a majority of the outline of the second face 4b1 is located within the first face 4a1, more than 50% (including 50%) of the outline of the second face 4b1 on the outer surface of the closing portion 321 can fall within the first face 4a1, thereby improving the problem of hot cracking of the outline of the second face 4b1. Also, at least a portion of the outline of the molten pool formed by the second connecting portion 4b can be located within the first connecting portion 4a, thereby improving the problem of hot cracking of the molten pool outline of the second connecting portion 4b and increasing the conductivity and connection strength between the conductive portion 20 and the closing portion 321.

[0221] For example, during laser welding, a first connecting portion 4a can be obtained first by laser welding, and the first connecting portion 4a can be used as a root weld. Then, a second connecting portion 4b can be obtained by laser welding, and the second connecting portion 4b can be used as a main weld. The extension depth of the main weld is greater than the extension depth of the root weld, and at least part of the outline of the main weld is located within the root weld, which helps to improve the problem of hot cracking in the outlines of the root weld and the main weld.

[0222] In some embodiments of this application, the shape of the first face 4a1 matches the outline shape of the second face 4b1, with at least a majority of the outline of the second face 4b1 falling at the central position of the first face 4a1. The first face 4a1 may extend partially or circumferentially along the outline of the second face 4b1 to match its shape. Furthermore, in embodiments of this application, "central position" is interpreted broadly, referring to either the exact center or near the exact center, meaning the minimum distance to the exact center is less than the minimum distance to the outline.

[0223] Therefore, by setting the shape of the first face 4a1 to match the outline shape of the second face 4b1, it is beneficial to make the outline of the second face 4b1 fall more within the first face 4a1, thereby further improving the problem of hot cracking of the outline of the second face 4b1. Furthermore, during laser welding, the first connecting portion 4a and the second connecting portion 4b can respectively present a shape that extends and gradually shrinks along the thickness direction of the converging portion 321. By setting at least most of the outline of the second face 4b1 in the central position of the first face 4a1, it is beneficial to make the molten pool outline of the second connecting portion 4b extending into the converging portion 321 fall more within the first connecting portion 4a, thereby further improving the problem of hot cracking of the outline of the second connecting portion 4b.

[0224] In some embodiments, referring to Figures 14 and 16-18, the surface of the gathering portion 321 can be elongated, the surface portion 411 is elongated and matches the length direction of the gathering portion 321, the first face 4a1 is an elongated shape extending along the length direction of the gathering portion 321, and two are spaced apart along the width direction of the gathering portion 321, the second face 4b1 is an elongated shape extending along the length direction of the gathering portion 321, and the two long sides of the second face 4b1 fall within the two first faces 4a1 respectively, so that the shape of the first face 4a1 matches the outline shape of the second face 4b1, and the outline of the second face 4b1 partially falls within the corresponding first face 4a1.

[0225] Therefore, one long side of the second face 4b1 can fall within one of the first faces 4a1, and the other long side of the second face 4b1 can fall within the other first face 4a1. Thus, the two long sides of the second face 4b1 can be located within the first connecting portion 4a respectively. Most of the outline of the second face 4b1 is less prone to hot cracking. Moreover, the molten pool outline extending from the two long sides of the second face 4b1 into the converging portion 321 can also be mostly located within the first connecting portion 4a. This can improve the problem of hot cracking in the outline of the second connecting portion 4b, and improve the conductivity and connection strength between the converging portion 321 and the conductive portion 20.

[0226] In some embodiments, referring to Figures 14 and 16-18, when the first face 4a1 is an elongated strip extending along the length direction of the converging portion 321 and two such strips are spaced apart along the width direction of the converging portion 321, and the second face 4b1 is an elongated strip extending along the length direction of the converging portion 321, and the two long sides of the second face 4b1 fall within the two first faces 4a1 respectively, if the outline of the second face 4b1 falls at least mostly in the center position of the first face 4a1, it indicates that the long side of the second face 4b1 extends along the length direction of the first face 4a1 and is located in the center position in the width direction of the first face 4a1. For example, during continuous laser welding, two root pass welds can be welded first along the length of the retracted portion 321, and then the main weld can be welded between the two root pass welds, so that the two long sides of the main weld fall within the two root pass welds respectively, and the long side of the main weld can fall at the center of the width of the root pass weld, which is conducive to the molten pool profile of the main weld falling more into the root pass weld, thereby improving the problem of hot cracking in the profile of the main weld.

[0227] For example, when the first face 4a1 is elongated, the first connecting part 4a can be made of spiral weld, which facilitates processing and helps to improve the quality of the weld.

[0228] For example, when the second face 4b1 is elongated, the second connecting part 4b can be welded with a spiral pattern, which facilitates processing and helps improve the quality of the weld.

[0229] In some embodiments, referring to Figures 15 and 19-21, there are multiple surface portions 411 arranged at intervals. Each surface portion 411 includes a first face 4a1 and a second face 4b1. The first face 4a1 is annular and surrounds the corresponding second face 4b1. The outline of the second face 4b1 is located within the corresponding first face 4a1, so that the shape of the first face 4a1 matches the outline shape of the second face 4b1. The annular shape can be, but is not limited to, a circular ring; for example, it can also be a polygonal ring, such as a rectangular ring, etc.

[0230] Therefore, the outline of the second face 4b1 falls entirely within the corresponding first face 4a1, and the entire circumference of the outline of the second face 4b1 is located within the first connecting portion 4a. The outline of the second face 4b1 is less prone to hot cracking. Moreover, the outline of the molten pool extending from the outline of the second face 4b1 into the converging portion 321 can also be mostly located within the first connecting portion 4a, thereby improving the problem of hot cracking in the outline of the second connecting portion 4b and increasing the conductivity and connection strength between the converging portion 321 and the conductive portion 20.

[0231] In some embodiments, when the first face 4a1 is annular and surrounds the second face 4b1, and the outline of the second face 4b1 is located within the first face 4a1, if the outline of the second face 4b1 at least largely falls within the center of the first face 4a1, it indicates that the outline of the second face 4b1 extends along the annular trajectory of the first face 4a1 and is located at the center between the inner and outer rings of the annular first face 4a1. For example, during pulsed laser welding, multiple annular root pass welds can be welded first, and then the main weld can be welded within each root pass weld, so that the outline of the main weld falls entirely within the annular root pass welds, for example, on the central ring line of the annulus. This facilitates the main weld's molten pool outline falling more into the root pass welds, improving the problem of hot cracking in the main weld's outline.

[0232] In some embodiments of this application, referring to FIG10, the extension depth G1 of the first connecting portion 4a is 60%-100% of the thickness T1 of the compacted region 3211. Thus, the first connecting portion 4a extends only from the surface of the closing portion 321 into the closing portion 321, and the extension depth exceeds half the thickness of the compacted region 3211. In this case, the molten pool depth of the first connecting portion 4a is not too large, requiring less energy during welding, thus reducing the likelihood of hot cracking in the contour and improving the conductivity and connection strength between the closing portion 321 and the conductive portion 20. Furthermore, the molten pool depth of the first connecting portion 4a is not too small, allowing the contour of the second connecting portion 4b to fall more into the first connecting portion 4a, thereby mitigating the problem of hot cracking in the contour of the second connecting portion 4b.

[0233] In some embodiments of this application, referring to FIG10, the connecting portion 4 further includes a third connecting portion 4c, the extension depth G3 of the third connecting portion 4c being less than the extension depth G1 of the first connecting portion 4a, the third connecting portion 4c being disposed on the side of the first connecting portion 4a away from the second connecting portion 4b, and the surface portion 411 further includes a third face 4c1 formed by the third connecting portion 4c on the outer surface of the converging portion 321, at least a portion of the outline of the first face 4a1 being located within the third face 4c1.

[0234] Since the connecting portion 4 extends from the outer surface of the gathering portion 321 toward the conductive portion 20, and the connecting portion 4 includes a third connecting portion 4c, the third connecting portion 4c extends from the outer surface of the gathering portion 321 toward the conductive portion 20, thereby including a third face portion 4c1 formed on the outer surface of the gathering portion 321. Exemplarily, the connecting portion 4 includes only a first connecting portion 4a, a second connecting portion 4b, and a third connecting portion 4c, so that the connecting portion 4 is composed of the first connecting portion 4a, the second connecting portion 4b, and the third connecting portion 4c, and the surface portion 411 is composed of the first face portion 4a1, the second face portion 4b1, and the third face portion 4c1. However, this application is not limited to this; the connecting portion 4 may also include other portions besides the first connecting portion 4a, the second connecting portion 4b, and the third connecting portion 4c.

[0235] In the above technical solution, since the extension depth G3 of the third connecting portion 4c is less than the extension depth G1 of the first connecting portion 4a, the energy required for the third connecting portion 4c during laser welding is smaller, and the contour of the third connecting portion 4c is less prone to hot cracking. Furthermore, since the third connecting portion 4c is located on the side of the first connecting portion 4a away from the second connecting portion 4b, at least a portion of the contour line of the first face 4a1 is located within the third face 4c1, thereby improving the problem of hot cracking in the contour line of the first face 4a1. Additionally, at least a portion of the contour line of the molten pool formed by the first connecting portion 4a can also be located within the third connecting portion 4c, thus further improving the problem of hot cracking in the contour of the molten pool of the first connecting portion 4a, and increasing the conductivity and connection strength between the conductive portion 20 and the closing portion 321.

[0236] For example, during laser welding, a first connecting portion 4a can be obtained first by laser welding, and the first connecting portion 4a can be used as a root weld. Then, a second connecting portion 4b can be obtained by laser welding, and the second connecting portion 4b can be used as a main weld. The extension depth G2 of the main weld is greater than the extension depth G1 of the root weld, and at least a portion of the outline of the main weld is located within the root weld. This helps to improve the problem of hot cracking in the outlines of the root weld and the main weld. Then, a third connecting portion 4c can be obtained by laser welding, and the third connecting portion 4c can be used as a repair weld. The extension depth G3 of the repair weld is less than the extension depth G1 of the root weld, and at least a portion of the outline of the root weld falls within the repair weld. This helps to improve the problem of hot cracking in the outlines of the root weld and the repair weld.

[0237] The repair weld can repair the entire outline of the root weld or only a portion of the root weld outline, depending on the actual situation. For example, in some embodiments, at least a majority of the outline of the first face 4a1 is located within the third face 4c1. Thus, more than 50% (including 50%) of the outline of the first face 4a1 can be repaired by the third connection portion 4c, thereby more effectively improving the problem of hot cracks appearing on the outline of the first face 4a1.

[0238] In some embodiments of this application, the shape of the third face 4c1 matches the outline shape of the first face 4a1, with at least a majority of the outline of the first face 4a1 falling at the center of the third face 4c1. The third face 4c1 may extend partially or circumferentially along the outline of the first face 4a1 to match its shape. For example, the first face 4a1 may be elongated, and the third face 4c1 may be an elongated shape extending along the length of the first face 4a1, with the long side of the first face 4a1 located at the center of the width of the third face 4c1. Alternatively, the first face 4a1 may be annular, and the third face 4c1 may be annular surrounding the first face 4a1, with the outer ring of the first face 4a1 located at the center between the inner and outer rings of the third face 4c1.

[0239] Therefore, by setting the shape of the third face 4c1 to match the outline shape of the first face 4a1, it is beneficial to make the outline of the first face 4a1 fall more within the third face 4c1, thereby further improving the problem of hot cracking of the outline of the first face 4a1. Furthermore, during laser welding, the first connecting part 4a and the third connecting part 4c can respectively present a shape that extends along the thickness direction of the converging part 321 and gradually shrinks. By setting at least most of the outline of the first face 4a1 in the central position of the third face 4c1, it is beneficial to make the molten pool outline of the first connecting part 4a extending into the converging part 321 fall more within the third connecting part 4c, thereby further improving the problem of hot cracking of the outline of the first connecting part 4a.

[0240] For example, when the third face 4c1 is elongated, the third connecting part 4c can be welded with a spiral line, which facilitates processing and helps to improve the quality of the weld.

[0241] In some embodiments of this application, referring to FIG10, the extension depth G3 of the third connecting portion 4c is 20%-60% of the thickness T1 of the compacted region 3211. Therefore, the third connecting portion 4c extends only from the surface of the closing portion 321 into the closing portion 321, and the molten pool depth of the third connecting portion 4c is relatively small. This requires less energy during welding, thus reducing the likelihood of hot cracking in the contour, which is beneficial for improving the conductivity and connection strength between the closing portion 321 and the conductive portion 20. Furthermore, the molten pool depth of the third connecting portion 4c is not too small, allowing more of the contour of the first connecting portion 4a to fall into the third connecting portion 4c, thereby mitigating the problem of hot cracking in the contour of the first connecting portion 4a.

[0242] For example, referring to Figure 10, the laser weld includes a root pass weld, a main weld, and a repair weld. The root pass weld is welded first, and its penetration depth G1 is 60% to 120% of the thickness T1 of the compacted region. For example, the penetration depth G1 of the root pass weld can be equal to the thickness T1 of the compacted region. The main weld is welded in the second batch. While meeting the requirements of flow area and welding process, the main weld must ensure that its outline falls in the center of the root pass weld. The repair weld is welded in the third batch. The center of the repair weld is located within the outline of the root pass weld, and its penetration depth G3 is 20% to 60% of the thickness T1 of the compacted region. The molten pool outline of the root pass weld is free of hot cracks, and 60% to 100% of the outline of the molten pool after the root pass weld and the main weld are within the compacted region.

[0243] Regardless of whether the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20 or from the conductive portion 20 toward the outer surface of the closing portion 321, the connecting portion 4 includes an inner portion 412 formed within the closing portion 321. In some embodiments of this application, referring to FIG7, at least a majority of the outline 4y of the inner portion 412 can be disposed in the compacted region 3211, that is, more than 50% (including 50%) of the outline of the portion of the connecting portion 4 formed within the closing portion 321 is located within the compacted region 3211. For example, the entire outline of the portion of the connecting portion 4 formed within the closing portion 321 can be disposed within the compacted region 3211; or, for another example, a portion of the outline of the portion of the connecting portion 4 formed within the closing portion 321 falls within the compacted region 3211, and the remainder falls within the fluffy region 3212, and the proportion of the portion falling within the compacted region 3211 is greater than the proportion of the portion falling within the fluffy region 3212.

[0244] Thus, in the above technical solution, since at least most of the outline of the portion of the connecting part 4 formed in the converging part 321 is provided in the compaction region 3211, the multilayer tabs 320 in the compaction region 3211 are very tightly bonded together with no or almost no interlayer gaps. This can improve the problem of hot cracks appearing in the weld outline due to interlayer gaps, thereby improving the conductivity yield and connection strength of the tab 32 and the conductive part 20, and improving the reliability of the battery cell 102.

[0245] In some embodiments of this application, more than 60% (including 60%) of the outline 4y of the inner portion 412 falls within the compaction region 3211. Therefore, by ensuring that more than 60% of the outline 4y of the inner portion 412 falls within the compaction region 3211, it is beneficial to further improve the problem of hot cracking in the molten pool outline of the connecting portion 4 falling within the converging portion 321. Furthermore, when the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20, most of the outline of the first portion 41 is the outline 4y of the inner portion 412. When more than 60% of the outline 4y of the inner portion 412 falls in the compacted area 3211, it is beneficial to increase the proportion of the outline of the first portion 41 falling in the compacted area 3211 relative to falling in the fluffy area 3212. This can improve the problem of thermal cracking of the outline of the first portion 41 formed on the closing portion 321, further improve the conductivity and connection strength of the tab portion 32 and the conductive portion 20, and improve the reliability of the battery cell 102.

[0246] In some embodiments of this application, when the connecting portion 4 extends from the outer surface of the closing portion 321 toward the conductive portion 20, and more than 60% of the outline 4x of the surface portion 411 falls in the compacted region 3211, and more than 60% of the outline 4y of the inner portion 412 also falls in the compacted region 3211, it is beneficial to further increase the proportion of the outline of the first portion 41 falling entirely in the compacted region 3211 relative to falling in the fluffy region 3212, which can improve the problem of thermal cracking of the outline of the first portion 41 of the connecting portion 4 formed in the closing portion 321 as a whole.

[0247] In some embodiments of this application, referring to FIG7, at least a majority of the volume of the internal portion 412 falls within the compaction region 3211. That is, more than 50% (including 50%) of the volume of the internal portion 412 is located within the compaction region 3211. Since there are no or almost no interlayer gaps between the multilayer tabs 320 within the compaction region 3211, pores caused by interlayer gaps are less likely to appear in the molten pool of the compaction region 3211. In this embodiment, by setting at least a majority of the volume of the internal portion 412 in the compaction region 3211, it is beneficial to reduce the pores formed in the internal portion 412, thereby improving the flow energy of the connection portion 4.

[0248] In some embodiments of this application, the area ratio of the compacted region 3211 relative to the converging portion 321 is greater than or equal to 40%. Here, the area ratio can be understood as the ratio of the total area of ​​the compacted region 3211 on the outer surface of the converging portion 321 to the area of ​​the outer surface of the converging portion 321.

[0249] Therefore, by setting the area ratio of the compacted region 3211 to be greater than or equal to 40%, it is beneficial to increase the coverage of the compacted region 3211 on the gathering part 321, which is beneficial to the design of the connecting part 4, so that the connecting part 4 can be more distributed in the compacted region 3211, improve the problem of thermal cracking in the outline of the connecting part 4, improve the conductivity and connection strength of the tab part 32 and the conductive part 20, improve the problem of air holes in the connecting part 4, improve the current carrying capacity of the connecting part 4, and thus improve the reliability of the battery cell 102.

[0250] For example, the area ratio of the compacted region 3211 to the converging portion 321 is greater than or equal to 60%. This allows a large portion of the converging portion 321 to be the compacted region 3211, which is beneficial for the design of the connecting portion 4. This allows the connecting portion 4 to be more widely distributed within the compacted region 3211, improving the problem of thermal cracking in the contour of the connecting portion 4, increasing the conductivity and connection strength between the tab portion 32 and the conductive portion 20, improving the problem of pores within the connecting portion 4, and enhancing the current carrying capacity of the connecting portion 4, thereby improving the reliability of the battery cell 102.

[0251] In some embodiments of this application, the compaction rate of the compacted region 3211 is greater than or equal to 6%. Therefore, by setting the compaction rate of the compacted region 3211 to be greater than or equal to 6%, the interlayer gaps in the compacted region 3211 can be reduced, and the portion of the connecting part 4 falling into the compacted region 3211 is less prone to thermal cracking and porosity, thus improving the overall flow capacity of the connecting part 4, as well as the reliability and conductivity yield of the connection between the connecting part 4 and the conductive part 20 and the gathering part 321.

[0252] For example, the compaction rate of the compaction region 3211 is greater than or equal to 12%, which can further reduce the gap in the compaction region 3211, making the compaction region 3211 almost gapless. The part of the connecting part 4 falling into the compaction region 3211 is less likely to have thermal cracks and pores, thereby improving the overall flow capacity of the connecting part 4, as well as the reliability and conductivity yield of the connecting part 4 connecting the conductive part 20 and the gathering part 321.

[0253] The following seven sets of experiments were conducted for comparison. In each experimental sample, 50 layers of tabs were stacked in the tab part, the thickness of a single tab was 13μm, and the theoretical thickness T2 of the tab part was 650μm.

[0254] Experiment 1 obtained the ultrasonic pre-welding effect and laser welding effect of Comparative Example 1. Figure 22 shows the local cross-sectional morphology of the converging part of Comparative Example 1. It can be seen that the thickness T1 of the compacted area is 765μm, and the calculated compaction rate is -17.7%. Figure 23 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that the outline of the laser weld has thermal cracks, and the proportion of thermal cracks is close to 100%.

[0255] Experiment 2 obtained the ultrasonic pre-welding effect and laser welding effect of Comparative Example 2. Figure 24 shows the local cross-sectional morphology of the converging part of Comparative Example 2. It can be seen that the thickness T1 of the compacted area is 711 μm, and the calculated compaction rate is -9.4%. Figure 25 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that the outline of the laser weld has hot cracks, and the proportion of hot cracks is close to 70%.

[0256] Experiment 3 obtained the ultrasonic pre-welding effect and laser welding effect of Comparative Example 3. Figure 26 shows the local cross-sectional morphology of the converging part of Comparative Example 3. It can be seen that the thickness T1 of the compacted area is 664 μm, and the calculated compaction rate is -2.2%. Figure 27 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that the outline of the laser weld has hot cracks, and the proportion of hot cracks is close to 40%.

[0257] Experiment 4: The ultrasonic pre-welding effect and laser welding effect of Example 1 were obtained. Figure 28 shows the local cross-sectional morphology of the converging part of Example 1. It can be seen that the thickness T1 of the compacted area is 609 μm, and the calculated compaction rate is 6.3%. Figure 29 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that a small number of hot cracks appear in the outline of the laser weld, and the proportion of hot cracks is close to 15%.

[0258] Experiment 5: The ultrasonic pre-welding effect and laser welding effect of Example 2 were obtained. Figure 30 shows the local cross-sectional morphology of the converging part of Example 2. It can be seen that the thickness T1 of the compacted area is 564μm, and the calculated compaction rate is 13.2%. Figure 31 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that the outline of the laser weld is almost free of thermal cracks.

[0259] Experiment 6: The ultrasonic pre-welding effect and laser welding effect of Example 3 were obtained. Figure 32 shows the local cross-sectional morphology of the converging part of Example 3. It can be seen that the thickness T1 of the compacted area is 522 μm, and the calculated compaction rate is 19.7%. Figure 33 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that the outline of the laser weld has no thermal cracks.

[0260] Experiment 7: The ultrasonic pre-welding effect and laser welding effect of Example 4 were obtained. Figure 34 shows the local cross-sectional morphology of the converging part of Example 4. It can be seen that the thickness T1 of the compacted area is 362 μm, and the calculated compaction rate is 44.3%. Figure 35 shows the local cross-sectional morphology of the converging part and the conductive part after laser welding. It can be seen from the figure that there are no thermal cracks in the outline of the laser weld.

[0261] Through the above experimental comparison, it can be found that when the compaction rate exceeds 6%, the problem of hot cracking in the profile of laser weld can be significantly improved, and when the compaction rate exceeds 12%, the profile of laser weld can be basically free of hot cracks.

[0262] This application also provides a battery 100, including a battery cell 102 of any of the above-described embodiments. Since the reliability of the battery cell 102 according to the embodiments of this application is improved, the reliability of the battery 100 is thus enhanced. It is worth noting that the battery 100 according to the embodiments of this application may or may not include a casing 101.

[0263] For example, the battery 100 also includes a busbar component, and multiple battery cells 102, at least two of which are electrically connected through the busbar component. This allows for the series and / or parallel connection of multiple battery cells 102. For instance, when multiple battery cells 102 are connected in series, the anode of one battery cell 102 is connected to the cathode of the next battery cell 102 through one busbar component, while the cathode of that battery cell 102 is connected to the anode of the previous battery cell 102 through another busbar component. For example, the busbar component can be directly or indirectly electrically connected to the electrode body 21 in the electrode component 2 to achieve electrical connection between the battery cell 102 and the busbar component.

[0264] This application also provides an electrical device including a battery 100 from any of the above-described embodiments. The battery 100 provides electrical energy to the electrical device. The electrical device can be any of the aforementioned devices or systems using the battery 100. Because the reliability of the battery 100 is improved, it is beneficial to improve the power consumption performance of the electrical device.

[0265] Referring to Figures 36 and 37, this application embodiment also provides an ultrasonic welding device 2000, including: a drive cylinder 600, a welding seat 500, and a welding head 400. The drive cylinder 600 is located on the side of the welding head 400 away from the welding seat 500 and is used to drive the welding head 400 to move toward the welding seat 500. Referring to Figures 8 and 9, the welding end 401 of the welding head 400 has welding teeth 5 and tooth grooves 6. The welding teeth 5 are divided into a plurality of spaced teeth 51 by the tooth grooves 6. The ultrasonic welding device 2000 is used to process the converging part 321 in any of the above embodiments, and the welding teeth 5 are used to process the compacted area 3211.

[0266] In ultrasonic welding, the compacted area 3211 corresponding to a single tooth 51 can be a common geometric shape such as a circle, square, or triangle, or a combination of these shapes. The welding tooth 5 corresponds to the compacted area 3211 in the ultrasonic welding, and the tooth groove 6 corresponds to the fluffy area 3212 in the ultrasonic welding. From the cross-sectional metallographic view of the ultrasonic welding, it can be seen that the tab 320 in the compacted area 3211 is compressed and deformed, the foil thickness becomes thinner and turns grayish-white, and the tab 320 in the fluffy area 3212 is bright silver.

[0267] For example, referring to Figures 36 and 37, the drive cylinder 600 is directly above the ultrasonic welding device 2000. Below the drive cylinder 600, the welding head 400 is connected via guide rails, conversion blocks, etc. The drive cylinder 600, welding head 400, and welding seat 500 are arranged sequentially from top to bottom in a straight line, making the ultrasonic welding process more stable, reducing mechanical wear, and minimizing the deformation of the welding head 400. During welding, the multilayer electrode tabs 320 to be welded can be placed between the welding head 400 and the welding seat 500. The drive cylinder 600 operates, pushing the welding head 400 downwards towards the welding seat 500. The welding head 400 and the welding seat 500 weld the multilayer electrode tabs 320 together, forming an ultrasonic weld mark. The type of drive cylinder 600 is not limited; for example, it can be an electric cylinder, hydraulic cylinder, pneumatic cylinder, etc. The shape of the welding seat 500 is not limited; for example, it can be a typical serrated surface.

[0268] In the embodiments of this application, the thickness T1 of the compacted region 3211 is less than the theoretical thickness T2 of the tab 32, resulting in a compaction rate of the compacted region 3211 greater than 0%. This indicates that the tab 320 in the compacted region 3211 needs to be compressed and yielded, and undergo plastic deformation. Therefore, according to the ultrasonic welding apparatus 2000 of this application embodiment, the surface pressure provided by the welding head 400 is greater than the yield strength of the tab 320, such as aluminum foil.

[0269] For example, under ultrasonic conditions, the yield strength Rp0.2 of the electrode tab 320, such as aluminum foil, is σ; the length of the welding end 401 of the welding head 400 is J1; the width of the welding end 401 is J2; the area of ​​the welding end 401 of the welding head 400 is S = J1 × J2; when the drive cylinder 600 is a cylinder, the pressure provided by the cylinder is P; the diameter of the cylinder is d; and the surface pressure provided by the welding head 400 is Pπ(d / 2). 2 / S, where, when Pπ(d / 2) 2 When / S≥σ, the tab 320 can be compressed and yielded and undergo plastic deformation, so that the compaction rate of the compacted region 3211 can be greater than 0%.

[0270] Therefore, on the one hand, the surface pressure of the welding head 400 can be increased by increasing the pressure provided by the cylinder to P, increasing the diameter of the cylinder to d, and reducing the area S of the welding end 401 to make the tab 320 yield and compact. On the other hand, the welding energy during ultrasonic welding can be increased. The cavitation effect of ultrasound and the heat generated by the vibration and friction of the tab 320 will reduce the yield strength of the tab 320, thereby increasing the compaction rate of the compaction area 3211.

[0271] For example, when the drive cylinder 600 is a pneumatic cylinder, after the welding head 400 is selected, the area S of the welding end 401 is fixed, and the air pressure supplied to the cylinder in the ultrasonic welding device 2000 can be adjusted to the maximum. For example, the upper limit of the air pressure supplied to the factory is usually 0.6 MPa. After welding with a cylinder with a diameter of 100 mm or 125 mm, the surface pressure provided by the welding head 400 is still less than the yield strength of the electrode tab 320, such as aluminum foil. By increasing the diameter of the cylinder to be greater than 125 mm, the surface pressure provided by the welding head 400 can be increased.

[0272] As described above, if the tab 320 needs to be compressed and yielded and undergo plastic deformation, the surface pressure provided by the welding head 400 of the ultrasonic welding device 2000 must be greater than the yield strength of the tab 320, such as aluminum foil, according to the above formula Pπ(d / 2). 2 Since S≥σ, it can be seen that when it is necessary to increase the diameter of the cylinder, it can be calculated according to the formula d≥√4σS / Pπ.

[0273] For example, the size of the ultrasonic weld mark needs to meet 11mm × 22mm, the amplitude A of the ultrasonic welding device 2000 is 25μm, the pressure provided by the cylinder is P = 0.41MPa, and the welding energy during ultrasonic welding is E = 500J. The compaction rate is increased by increasing the welding time. The tab 320 is a rolled 1-series aluminum alloy with a yield strength of Rp0.2 = 75MPa. Under this ultrasonic condition, the yield strength of the aluminum foil decreases to Rp0.2 (ultrasonic action) = 35MPa. According to the formula, d ≥ √[(4 × 35 × 11 × 22) / (0.41 × π)], that is, d ≥ 162mm, which can make the aluminum tab yield and compact, so that the compaction rate of the compacted area 3211 can be greater than 0%.

[0274] For example, the cylinder has a diameter of 200 mm. As a result, the cylinder is easier to manufacture and can be put into operation. Moreover, it has a high compaction rate, which can effectively improve the problem of hot cracking in the contour of the laser weld, improve the conductivity and connection strength of the tab 32 and the conductive part 20, reduce the porosity in the molten pool of the laser weld, improve the current carrying capacity of the laser weld, and improve the reliability of the battery cell 102.

[0275] For example, when the drive cylinder 600 is an electric cylinder, after the welding head 400 is selected, the area S of the welding end 401 is fixed, and the pressure that the electric cylinder can provide is F. When F / S≥σ, the pole tab 320 can be compressed and yielded and undergo plastic deformation, so that the compaction rate of the compaction area 3211 can be greater than 0%.

[0276] In some embodiments of this application, the area ratio of the teeth on the welding end 401 is greater than or equal to 40%. It is worth noting that "the area ratio of the teeth on the welding end 401" refers to the ratio of the area of ​​the welding teeth 5 to the area of ​​the welding end 401, or the ratio of the sum of the areas of all teeth 51 to the area of ​​the welding end 401, or the ratio of the difference between the toothless area of ​​the welding end 401 and the area of ​​the tooth groove on the welding end to the toothless area of ​​the welding end 401.

[0277] When the area ratio of the teeth at the welding end 401 is greater than or equal to 40%, after ultrasonic pre-welding, the area ratio of the compacted area 3211 relative to the converging part 321 can be greater than or equal to 40%. Thus, by setting the area ratio of the teeth at the welding end 401 to be not less than 40%, the area ratio of the compacted area 3211 in the ultrasonic welding can be increased, making the area ratio of the compacted area 3211 relative to the converging part 321 greater than or equal to 40%. This allows the outline of the laser weld to fall more into the compacted area 3211, thereby improving the problem of thermal cracking in the outline of the laser weld to a greater extent. This, in turn, improves the conductivity and connection strength between the tab 32 and the conductive part 20, and enhances the reliability of the battery cell 102.

[0278] For example, the area ratio of the teeth at the welding end 401 is greater than or equal to 60%, which can further increase the area ratio of the compacted area 3211 in the ultrasonic welding, so that the area ratio of the compacted area 3211 relative to the converging part 321 is greater than or equal to 60%, thereby allowing the outline of the laser weld to fall more into the compacted area 3211, so as to improve the problem of thermal cracking in the outline of the laser weld to a greater extent, thereby improving the conductivity and connection strength of the tab 32 and the conductive part 20, and improving the reliability of the battery cell 102.

[0279] For example, by adjusting the welding teeth 5, the area ratio of the compacted region 3211 to the converging portion 321 is 60% to 100%, providing a sufficiently large compacted region 3211 for laser welding. Furthermore, 60% to 100% of the laser weld contour can be set within the compacted region 3211. For instance, viewed from the outer surface of the converging portion 321, 60% to 100% of the laser weld contour falls within the compacted region 3211. Similarly, viewed from the cross-section of the converging portion 321, i.e., from its interior, 60% to 100% of the laser weld contour also falls within the compacted region 3211. This effectively improves the problem of hot cracking in the laser weld contour, increases the conductivity and connection strength between the tab 32 and the conductive portion 20, and enhances the reliability of the battery cell 102.

[0280] In the embodiments of this application, by improving the distribution, shape, and size of the compacted area 3211 in the gathering portion 321, and correspondingly matching the shape, size, and distribution position of the connecting portion 4, at least most of the outline of the connecting portion 4 formed by the connection between the conductive portion 20 and the tab portion 32 falls on the compacted area 3211 of the gathering portion 321. In this way, the problem of thermal cracking in the outline of the connecting portion 4 can be improved by utilizing the characteristic that the multilayer tabs 320 in the compacted area 3211 are very tightly bonded together, thereby improving the conductivity yield and connection strength of the tab portion 32 and the conductive portion 20, and enhancing the overcurrent capacity and reliability of the battery cell 102.

[0281] The following describes a specific embodiment of this application.

[0282] Referring to Figure 38, the welding end 401 of the welding head 400 divides the welding tooth 5 into two first tooth portions 514, multiple second tooth portions 515, and multiple third tooth portions 516 through the tooth groove 6. The contour of the first tooth portion 514 matches the contour of the second tooth portion 515, and the contour of the first tooth portion 514 matches the contour of the third tooth portion 516. The welding end 401 is elongated. The length direction of the first tooth 514 matches the length direction of the welding end 401, and the width direction of the first tooth 514 matches the width direction of the welding end 401. Two first teeth 514 are spaced apart along the width direction of the welding end 401. Each long side of the first tooth 514 has multiple protrusions 5141 spaced apart along the length direction of the welding end 401. The protrusions 5141 protrude toward the width direction of the welding end 401. Multiple second teeth 515 are disposed between the two first teeth 514, and the multiple second teeth 515 are spaced apart along the length direction of the welding end 401. The protrusions 5141 on one side of the two first teeth 514 are positioned opposite each other, so that two opposing protrusions 5141 are disposed between each two adjacent second teeth 515. Multiple third teeth 516 are spaced apart and arranged around the two first teeth 514.

[0283] The ratio of the tooth tip length S7 of the first tooth portion 514 in the longitudinal direction of the welding end 401 to the length J1 of the welding end 401 is 75%-85%. The ratio of the tooth tip width S8 of the first tooth portion 514 in the width direction of the welding end 401 to half of the width J2 of the welding end 401 is 75%-85%. The tooth area ratio is 70%-80%. Referring to Figure 39, the groove width W0 of each tooth groove 6 is 0.2mm-0.4mm. The tooth height H4 of the first tooth portion 514 is 0.25mm. The projected distance E4 between the tooth tip and the tooth root of the first tooth portion 514 is 0.1mm-0.2mm. The edge of the welding end 401 is rounded with a rounding radius R4 of 1.5mm. The tooth area ratio of the welding end 401 is 70%-80%. The length J1 of the welding end 401 is 25mm, and the width J2 is 14mm.

[0284] Referring to Figure 38, the third tooth 516 includes a first sub-tooth 5161 located on both sides of the two first tooth 514 in the width direction of the welding end 401, and a second sub-tooth 5162 located on both sides of the two first tooth 514 in the length direction of the welding end 401. There are multiple first sub-tooths 5161 and they are spaced apart along the length direction of the welding end 401. There are multiple second sub-tooths 5162 and they are spaced apart along the width direction of the welding end 401. The tooth tip width S9 of the first sub-tooth 5161 in the length direction of the welding end 401 is 1.8mm-2.2mm, and the tooth tip width S10 of the second sub-tooth 5162 in the width direction of the welding end 401 is 0.8mm-1.2mm.

[0285] The weld marks produced by the welding head in this embodiment are shown in Figures 13 and 40. The compaction area 3211 includes a first sub-area Z1 corresponding to the first tooth 514, a second sub-area Z2 corresponding to the second tooth 515, and a third sub-area Z3 corresponding to the third tooth 516. The first sub-area Z1 is elongated and matches the length and width directions of the converging portion 321, respectively. There are two first sub-areas Z1, which are spaced apart along the width direction of the converging portion 321. Each long side of the first sub-area Z1 has multiple protruding segments Z11 spaced apart along the length direction of the converging portion 321, and the protruding segments Z11 protrude toward the width direction of the converging portion 321. Multiple second sub-areas Z2 are located between the two first sub-areas Z1 and are spaced apart along the length direction of the converging portion 321. The protruding segments Z11 on the side closest to each other in the two first sub-areas Z1 are positioned opposite each other, and two opposing protruding segments Z11 are provided between each pair of adjacent second sub-areas Z2. Multiple third subregions Z3 are spaced apart around two first subregions Z1.

[0286] The ultrasonic weld mark and conductive part processed by the welding head in this embodiment are laser welded. The surface of the laser weld is shown in Figures 12 and 41. The two long sides 4x1 of the surface portion 411 are respectively located in the two first sub-regions Z1. The laser welding includes a main weld and a root weld. Both the main weld and the root weld are oscillating welded in a spiral. The two long sides of the main weld fall within the root weld, and the outer long side of the root weld forms the two long sides 4x1 of the surface portion 411. The interior of the laser weld is shown in Figures 11 and 42-44. Most of the outline of the interior portion 412 falls within the compaction region 3211, and the outline of the laser weld is free of hot cracks.

[0287] In this embodiment, the use of a large-diameter cylinder, combined with a welding head having two large, elongated teeth, can effectively increase the area ratio of the compaction area 3211 relative to the welding end 401. Furthermore, multiple small teeth are provided between and around the two large, elongated teeth to provide welding gripping force, which firmly grips the foil during welding and provides greater friction.

[0288] Another specific embodiment of this application is described below.

[0289] Referring to Figure 45, the welding end 401 of the welding head 400 is divided into welding teeth 5 by the first straight groove 61 and the second straight groove 62 in the tooth groove 6. The welding end 401 is elongated. There are multiple first straight grooves 61 arranged in parallel. The length direction of the first straight groove 61 is parallel to the width direction of the welding end 401. The length direction of the second straight groove 62 is parallel to the length direction of the welding end 401 and is located in the center of the width of the welding end 401. The second straight groove 62 intersects with multiple first straight grooves 61 to define multiple elongated fourth teeth 513. The welding end 401 presents a double-row elongated grid shape.

[0290] The fourth tooth 513 has a tooth tip dimension S5 of 2mm-2.4mm in the spacing direction of the first straight groove 61, and a tooth tip dimension S6 of 3.5mm-4.5mm in the length direction of the first straight groove 61. The groove width W1 of the first straight groove 61 is 0.2mm-0.4mm, the groove width W2 of the second straight groove 62 is 0.4mm-0.6mm, the tooth height of the fourth tooth 513 is 0.2mm, and the projected distance between the tooth tip and the tooth root of the fourth tooth 513 is 0.1mm-0.2mm. The edge of the welding end 401 is rounded with a rounding radius of 1.5mm. The tooth area ratio of the welding end 401 is 60%-70%. The length J1 of the welding end 401 is 25mm, and the width J2 is 12mm.

[0291] The weld mark processed by the welding head in this embodiment is shown in Figures 14 and 46. The compaction area 3211 includes a fourth sub-region Z5 corresponding to the fourth tooth 513. Multiple fourth sub-regions Z5 are arranged in a row along the length direction of the ultrasonic weld mark. Two rows of fourth sub-regions Z5 are arranged on the ultrasonic weld mark. The ultrasonic weld mark processed by the welding head in this embodiment is laser welded to the conductive part. The surface of the laser weld is shown in Figures 14 and 47. The two long sides 4x1 respectively pass through the two rows of fourth sub-regions Z5. The laser welding includes a main weld and a root weld. Both the main weld and the root weld are oscillating welded using a spiral. The two long sides of the main weld fall within the root weld. The outer long side of the root weld constitutes the two long sides 4x1 of the surface part 411. The interior of the laser weld is shown in Figures 11 and 48. Most of the outline of the interior part 412 falls within the compaction area 3211. The outline of the laser weld is free of hot cracks.

[0292] Another specific embodiment of this application is described below.

[0293] Referring to Figure 49, the welding end 401 of the welding head 400 is divided into welding teeth 5 by the first straight groove 61 and the second straight groove 62. The welding end 401 is elongated. There are multiple first straight grooves 61 arranged in parallel. The length direction of the first straight groove 61 is parallel to the width direction of the welding end 401. The length direction of the second straight groove 62 is parallel to the length direction of the welding end 401 and is located in the center of the width of the welding end 401. The second straight groove 62 intersects with the multiple first straight grooves 61 to define multiple fifth teeth 517. The welding end 401 presents a double-row square shape.

[0294] The fifth tooth 517 has a tooth tip dimension S11 of 4.5mm-5.5mm in the spacing direction of the first straight groove 61, and a tooth tip dimension S12 of 5mm-6mm in the length direction of the first straight groove 61. The groove width W1 of the first straight groove 61 is 0.3mm-0.9mm, the groove width W2 of the second straight groove 62 is 0.3mm-0.9mm, and the tooth area ratio of the welding end 401 is 70%-90%. The length J1 of the welding end 401 is 22mm, and the width J2 is 12mm.

[0295] The weld mark processed by the welding head in this embodiment is shown in Figures 50 and 51. The compacted area 3211 includes a fifth sub-area Z6 corresponding to the fifth tooth 517. Multiple fifth sub-areas Z6 are arranged in a row along the length direction of the ultrasonic weld mark. Two rows of fifth sub-areas Z6 are arranged on the ultrasonic weld mark. The ultrasonic weld mark processed by the welding head in this embodiment is laser welded to the conductive part. Referring to Figure 15, each fifth sub-area Z6 is provided with a laser weld. Figures 52-55 show a schematic diagram of the laser weld at one of the fifth sub-areas. The laser welding includes a main weld and a root weld. The root weld is annular, and the main weld is circular. The outline of the laser weld is free of hot cracks. The root weld is welded first. The entire root weld falls within the compacted area, and the penetration depth of the root weld is exactly equal to the thickness of the compacted area. After the root weld is completed, the main weld is welded. The outer contour of the molten pool of the main weld falls inside the molten pool of the root weld.

[0296] Furthermore, the embodiments of this application are also applicable to batteries for 3C products, such as small batteries used in mobile phones and other devices. 3C product batteries have fewer tab layers and narrower tab widths. The welding head can be a flat-headed electro-spark etching head for roughening, or a welding head with a low tooth height (e.g., tooth height ≤ 0.1mm). For example, power batteries typically have 30-120 tab layers, with a tab thickness of 13μm-15μm and a tooth height of 0.1mm-0.4mm; while 3C product batteries typically have 10-50 tab layers, with a tab thickness of 6μm-10μm, an ultrasonic welding width of approximately 5mm, and a tooth height of less than 0.1mm. Laser welding can be performed using a high-frequency pulsed laser or a low-power continuous laser, ensuring that 60% to 100% of the laser weld contour falls within the compacted area to improve battery reliability.

[0297] In the production of battery cells, ultrasonic welding can be used to pre-weld multiple tabs in the electrode area to form an ultrasonic weld mark. Then, laser welding is used to weld the ultrasonic weld mark to the conductive part of the terminal component, realizing the connection and electrical conduction between the electrode assembly and the terminal component. However, in related technologies, the ultrasonic welding machine used for ultrasonic welding cannot form an effective interlayer weld after pre-welding the tabs. There are gaps between the multiple tabs. The existence of these gaps will increase the porosity in the molten pool of the laser weld, reducing the current carrying capacity of the battery cell. Furthermore, during the cooling stage after laser welding, the profile of the laser weld will develop thermal cracks, which will worsen the problem and affect the connection reliability and conductivity yield between the tabs and the conductive part, thus affecting the performance of the battery cell.

[0298] The ultrasonic welding apparatus provided in this application embodiment can increase the cylinder diameter, increase the welding pressure, increase the compaction rate after ultrasonic pre-welding, reduce the gap between the tab layers, and, in conjunction with the welding tooth design of the welding head, increase the area of ​​the compaction region and optimize the distribution of the compaction region. This helps to improve the problem of thermal cracking deterioration in the contour of the laser weld and reduce the proportion of pores in the laser weld pool. This improves the connection reliability and conductivity yield between the tab and the conductive part, enhances the current carrying capacity of the battery cell, and improves the performance of the battery cell.

[0299] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other.

[0300] The above are merely preferred embodiments of this application and are not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A battery cell, wherein, include: Housing components; An electrode component is disposed on the housing component, and the electrode component includes a conductive portion; An electrode assembly is housed in the housing component and includes an electrode tab portion. The electrode tab portion includes a plurality of stacked electrode tabs. The plurality of electrode tabs are connected to form a folded portion. The folded portion is stacked with and connected to the conductive portion to form a connecting portion. The gathering portion includes a compacted area, the thickness of which is less than the stacked thickness of the plurality of tabs in the tab portion. The connecting portion includes a first portion formed in the gathering portion, at least a majority of the outline of the first portion being located in the compacted area.

2. The battery cell according to claim 1, wherein, The connecting portion extends from the outer surface of the retractable portion toward the conductive portion, and the first portion includes a surface portion formed on the outer surface of the retractable portion.

3. The battery cell according to claim 2, wherein, At least a majority of the area of ​​the surface portion falls within the compacted region.

4. The battery cell according to claim 2 or 3, wherein, At least a majority of the outline of the surface portion falls within the compacted area.

5. The battery cell according to claim 4, wherein, More than 60% of the outline of the surface portion falls within the compacted area.

6. The battery cell according to any one of claims 2-5, wherein, The surface of the gathering part is elongated, and the surface portion is elongated and matches the length direction of the gathering part. At least most of each of the two long sides of the surface portion is located in the compaction area.

7. The battery cell according to claim 6, wherein, The compacted area includes a first sub-region, which is elongated and matches the length and width directions of the gathered portion, respectively. The length of the first sub-region exceeds half the length of the gathered portion. There are two first sub-regions, which are spaced apart along the width direction of the gathered portion. The two long sides of the surface portion are respectively located in the two first sub-regions.

8. The battery cell according to claim 7, wherein, Each long side of the first sub-region has a plurality of protruding segments spaced apart along the length direction of the converging portion, the protruding segments protruding toward the width direction of the converging portion.

9. The battery cell according to claim 8, wherein, The compacted area includes a plurality of second sub-regions disposed between the two first sub-regions and spaced apart along the length direction of the converging portion. The protruding segments of the two first sub-regions are positioned opposite each other on one side, and two opposing protruding segments are respectively disposed between each pair of adjacent second sub-regions.

10. The battery cell according to claim 9, wherein, The gathering portion includes a fluffy region, which includes a first fluffy area disposed between two first sub-regions and separated between the two first sub-regions and between the first sub-region and the second sub-region. The first fluffy area presents a linear form on the outer surface of the gathering portion so that the outline of the second sub-region matches the outline of the first sub-region.

11. The battery cell according to any one of claims 7-9, wherein, The compaction zone includes multiple third sub-regions, which are spaced apart and arranged around the two first sub-regions.

12. The battery cell according to claim 11, wherein, The gathering portion includes a fluffy region, which includes a second fluffy region located on the outer periphery of the two first sub-regions and separated between the first sub-regions and the third sub-regions, as well as separated between two adjacent third sub-regions. The second fluffy region is in the form of a line on the outer surface of the gathering portion so that the outline of the third sub-region matches the outline of the first sub-region.

13. The battery cell according to claim 6, wherein, The compacted area includes a plurality of first compacted rows spaced apart along the width direction of the gathered portion. Each first compacted row includes a plurality of fourth sub-regions spaced apart along the length direction of the gathered portion. The two long sides of the surface portion are respectively corresponding to two of the first compacted rows, and each long side passes through a plurality of the fourth sub-regions in the corresponding first compacted row. The size of the fourth sub-region in the length direction of the gathered portion is greater than the distance between two adjacent fourth sub-regions in the length direction of the gathered portion.

14. The battery cell according to claim 13, wherein, The first compacted row consists of two parts. The fourth sub-region is elongated and its length direction matches the width direction of the converging part. The width direction of the fourth sub-region matches the length direction of the converging part. The length of the fourth sub-region exceeds one-quarter of the width of the converging part.

15. The battery cell according to claim 13 or 14, wherein, The gathering portion includes a fluffy region, which includes a third fluffy region separated between two adjacent fourth sub-regions in the same first compaction row, and a fourth fluffy region separated between two adjacent first compaction rows. The third fluffy region is in the form of a line extending along the width direction of the gathering portion on the outer surface of the gathering portion, and the fourth fluffy region is in the form of a line extending along the length direction of the gathering portion on the outer surface of the gathering portion. The width of the third fluffy region is smaller than the width of the fourth fluffy region.

16. The battery cell according to any one of claims 2-5, wherein, The entire surface portion is located within the compacted area.

17. The battery cell according to claim 16, wherein, The compacted area includes a plurality of fifth sub-regions spaced apart, and the surface portion is a plurality of spaced-apart portions that correspond one-to-one with the plurality of fifth sub-regions.

18. The battery cell according to claim 17, wherein, The compaction area includes a plurality of second compaction rows spaced apart along the width direction of the gathered portion, and each second compaction row includes a plurality of fifth sub-regions spaced apart along the length direction of the gathered portion.

19. The battery cell according to claim 18, wherein, The second compaction row consists of two parts, and the fifth sub-region has a dimension in both the width direction and the length direction of the gathering part that exceeds one-quarter of the width of the gathering part.

20. The battery cell according to any one of claims 2-19, wherein, The connecting portion includes a first connecting portion and a second connecting portion, the second connecting portion extending into the conductive portion, the extension depth of the first connecting portion being less than the extension depth of the second connecting portion, the surface portion including a first facet formed by the first connecting portion on the outer surface of the gathering portion, and a second facet formed by the second connecting portion on the outer surface of the gathering portion, at least a majority of the outline of the second facet being located within the first facet.

21. The battery cell according to claim 20, wherein, The shape of the first face matches the outline shape of the second face, and at least a majority of the outline of the second face falls in the center of the first face.

22. The battery cell according to claim 20 or 21, wherein, The surface of the gathering part is elongated, and the surface portion is elongated and matches the length direction of the gathering part. The first face is an elongated shape extending along the length direction of the gathering part and two of them are spaced apart along the width direction of the gathering part. The second face is an elongated shape extending along the length direction of the gathering part, and the two long sides of the second face fall within the two first faces respectively.

23. The battery cell according to claim 20 or 21, wherein, The surface portions are multiple and spaced apart. Each surface portion includes a first face and a second face. The first face is annular and surrounds the corresponding second face. The outline of the second face is located within the corresponding first face.

24. The battery cell according to any one of claims 20-23, wherein, The extension depth of the first connecting portion is 60%-100% of the thickness of the compacted region.

25. The battery cell according to any one of claims 20-24, wherein, The connecting portion further includes a third connecting portion, the extension depth of the third connecting portion being less than the extension depth of the first connecting portion, the third connecting portion being disposed on the side of the first connecting portion away from the second connecting portion, and the surface portion further includes a third facet formed by the third connecting portion on the outer surface of the gathering portion, at least a portion of the outline of the first facet being located within the third facet.

26. The battery cell according to claim 25, wherein, At least a majority of the outline of the first face is located within the third face.

27. The battery cell according to claim 26, wherein, The shape of the third face matches the outline shape of the first face, and at least a majority of the outline of the first face falls in the center of the third face.

28. The battery cell according to any one of claims 25-27, wherein, The extension depth of the third connection is 20%-60% of the thickness of the compacted region.

29. The battery cell according to any one of claims 1-28, wherein, The first portion includes an internal portion formed within the gathered portion, at least a majority of the outline of the internal portion falling within the compacted area.

30. The battery cell according to claim 29, wherein, More than 60% of the outline of the internal portion falls within the compacted area.

31. The battery cell according to claim 29 or 30, wherein, At least a majority of the volume of the internal portion falls within the compacted region.

32. The battery cell according to any one of claims 1-31, wherein, The compacted area accounts for more than 40% of the area of ​​the gathered portion.

33. The battery cell according to claim 32, wherein, The compacted area accounts for more than 60% of the area of ​​the gathered portion.

34. The battery cell according to any one of claims 1-33, wherein, The compaction rate of the compacted area is greater than or equal to 6%.

35. The battery cell according to claim 34, wherein, The compaction rate of the compacted area is greater than or equal to 12%.

36. A battery, wherein, Includes the battery cell according to any one of claims 1-35.

37. An electrical appliance, wherein, Includes the battery according to claim 36.

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