Busbar and battery

Abstract

The present application provides a bus bar and battery and relates to the technical field of battery manufacturing and processing. The battery includes a bus bar, one side of the bus bar forms a plurality of weld paths to be combined with a winding package, individual weld paths are distributed around the bus bar in a matrix-like manner, and the weld paths have smooth wave curves.

Description

The present application relates to the technical field of battery manufacture and processing, and more particularly to a power bus and battery.In the case of a cylindrical battery, welding of a busbar to a winding package is generally carried out by laser welding in order to ensure the strength of the connection and the flow cross section at the pole and at the connecting plate. In related technologies, the laser weld path between the battery busbar and the winding package may be a polyline weld path. In the polyline weld path, the speed of the laser beam in the vicinity of an inflection point must first be reduced to zero and then accelerated from zero. Alternatively, the laser weld path between the battery busbar and the winding package can also be a spiral curve weld path (see FIG. 1 ).In a polyline weld path, a large amount of laser energy accumulates at the inflection point, resulting in a large welding depth, and there is then a risk of weld-through. However, a spiral curve weld trace has multiple overlapping braze joints that are prone to over-welding, which in turn results in structural through-welding. All of the above problems result in poor quality of battery welding in related technologies.The object of the present invention is to provide a busbar and a battery with improved characteristics.This object is achieved by a busbar according to Claim 1 and a battery according to Claim 7.The present application provides a busbar. It comprises a welding side and a back side arranged opposite each other, wherein the welding side is configured for welding with a winding package, the back side is provided with a welding path and the welding path has a smooth wave-shaped curve.The present application further provides a battery. It comprises a winding package and a busbar according to one of the above configurations, wherein the welding side of the busbar and the tab of the winding package are welded, wherein the orthogonal projection of the welding path on the busbar onto the welding side overlaps with the tab.The present application provides a busbar. By forming the welding path as a smooth wave curve without crossing or overlapping, the welding path can hardly have inflection points, so that the welding energy at the inflection point can be reduced. The failure of the bus bar can be avoided, and the use of the spiral welding in the related technology can be avoided in which a plurality of overlapping points are generated on the bus bar, so that excessive welding energy can be avoided at the overlapping points on the bus bar, and then a plurality of welding paths are uniformly arranged on the bus bar. This can reinforce the connection between the busbar and the winding package and increase the flow cross section and at the same time improve the over-welding situation and improve the welding quality.Preferred exemplary embodiments of the present invention are explained in more detail below with reference to the attached drawings. The following are shown: FIG. 1 is a schematic structural view of a power bus bar in related art; FIG. 2 is a schematic structural view of a negative busbar according to an embodiment of the present application; FIG. 3 is a schematic structural view of a positive busbar according to an embodiment of the present application; FIG. 4 is another schematic structural view of the negative busbar according to an embodiment of the present application; FIG. 5 is another schematic structural view of the positive busbar according to an embodiment of the present application; FIG. 6 is a third schematic structural view of the negative busbar according to an embodiment of the present application; FIG. 7 is a schematic sectional view of a battery of an embodiment of the present application; and FIG. 8 is a schematic structural view of a tab according to an embodiment of the present application.In the description of the application, the terms "first" and "second" should not be understood as an explicit or in-depth indication of the relative importance or of the number of features involved. Instead, these are used merely for description. Thus, a feature more closely determined by "first" or "second" may expressly or implicitly mean that the number of this feature is one or more. In the specification of the present application, the term "plural" refers to a number of two or more unless otherwise specified.In related technologies, the battery bus bar includes a positive bus bar and a negative bus bar, and the positive bus bar needs to be welded between the positive bus bar and the winding package, and the negative battery and the winding package also need to be welded. In this way, the cells may be combined into a battery pack to power a power consumer. The welding between the battery bus bar and the winding package is more uniform, and the welding strength and the overcurrent capacity of a plurality of welding points between the battery bus bar and the winding package are better, and the welding effect is better.The welding path of the connecting structure between the battery busbar and the winding package is generally formed as a polygonal line and a spiral in related technologies, so that inflection points and overlapping points can easily occur, which leads to over welding between the battery busbar and the winding package.Reference is made to FIGS. 2 and 3. FIG. 2 is a schematic structural view of a negative busbar according to an embodiment of the present application.FIG. 3 is a schematic structural view of a positive busbar according to an embodiment of the present application. The present application provides a busbar. It has a welding side and a rear side arranged opposite each other, wherein the welding side is configured for welding with a winding package 3, the rear side is provided with a welding path 2, and the welding path 2 has a smooth wave-shaped curve.It is understood that the smooth wavy curve may be any curve that has no inflection points or overlapping points (no intersections), for example, a sinusoidal curve, a curve that consists of straight lines and curves without inflection points, or even a random curve.Namely, in the related technology, some welding paths are curved straight lines, and there are a plurality of inflection points, so that the laser beam needs to be accelerated in welding and then have a uniform speed in the straight line, and it needs to run more slowly as it approaches the inflection point until the speed of the laser beam falls to 0 when it reaches the inflection point, and then the speed of the laser beam again increases from 0, therefore, the energy accumulation of the laser beam at the inflection point is enormous, and it is easy to cause a large welding depth, and there is a risk of welding. However, when the welding path is formed spirally, there are a plurality of overlapping points although the welding path has no turn point, and the overlapping points in the welding path mean that the welding energy at this location is too high and the situation of over welding may easily occur, and the two situations have the problem of over welding to different extents, thereby affecting the welding effect.Advantageous effects of the present application: By forming the welding path 2 as a smooth wave curve without crossing or overlapping (the wave curve may be a smooth curve, a non-smooth curve, and a non-smooth wave curve may also have an inflection point), the welding path 2 may hardly have an inflection point, so that the welding energy at the inflection point can be reduced. The through welding of the bus bar can be avoided, and the use of the spiral welding in the related technology can be avoided in which a plurality of overlapping points are generated on the bus bar, so that excessive welding energy can be avoided at the overlapping points on the bus bar, and then a plurality of welding paths 2 are uniformly arranged on the bus bar. This can reinforce the connection between the busbar and the winding package 3 and increase the flow cross section and at the same time improve the over-welding situation and improve the welding quality.The bus bar in this embodiment is suitable for a cylindrical steel case cell, and can of course be used for batteries of other shapes (such as prismatic battery).In the embodiment of the present application, as shown in FIGS. 4 and 5, where FIG. 4 shows another schematic structural view of the negative busbar according to an embodiment of the present application and FIG. 5 shows another schematic structural view of the positive busbar according to an embodiment of the present application, the welding path 2 includes a plurality of semicircular portions 21 and a plurality of straight portions 22, and the plurality of semicircular portions 21 and the plurality of straight portions 22 are alternately arranged and connected to each other.Here, the alternating arrangement means that the straight portion 22 and the semicircular portion 21 are connected to each other at ends. One end of a straight portion 22 is connected to one end of a certain semicircular portion 21, and the other end of the straight portion 22 is connected to one end of another semicircular portion 21.It should be understood that the semicircular portion 21 is not limited to the semicircular curve, but may be a part of the elliptic curve, the straight portion 22 may be a straight line, or may be a curve having a certain arc dimension, the semicircular portion 21 and the straight portion 22 must be tangential to satisfy the condition that the total welding path is a smooth curve (without inflection point). The curve is generally regarded as a wavy curve, but the wavy curve is not limited to the curve consisting of the straight portion 22 and the semicircular portion 21.It is understood that a plurality of semicircular portions 21 and a plurality of straight portions 22 are alternately arranged and connected to each other to form a wave-shaped curved path, and that there are no overlapping points and inflection points on the path, which corresponds to an optimized structure of ordinary wave-shaped arcs.In the embodiment of the application, a wave-shaped curve is transformed into semicircular portions 21 and straight portions 22 which are alternately arranged and connected to each other. Thus, the width of the welding path 2 (i.e., the length along the length direction of the straight portion 22 in the wave curve and further the length along the circumferential direction of the bus bar) can be made wider, so that the welding path 2 can have a larger surface area on the bus bar and then make the welding contact area larger and more uniform. In this way, the connection strength between the busbar and the winding package 3 is higher, and the flow cross section between the busbar and the winding package 3 is larger, and then the overall effective flow cross section of the battery becomes larger, so that the problem that additional filling and welding must be performed for a void need not be taken into account.In the embodiment of the present application, as shown in FIGS. 4 and 5, a plurality of straight portions 22 are arranged parallel to each other and spaced apart from each other.It is understood that arranging a plurality of straight portions 22 parallel to each other and spaced apart from each other does not necessarily mean that the length of each straight portion 22 is the same. Rather, the lengths of a plurality of straight sections 22 in each welding path 2 can be of different lengths.Further, the straight portion 22 may also be a part of the circle around the center of the busbar (i.e., an arc at one end), and as long as the plurality of arcs (i.e., the straight portions 22) are parallel to each other, the diameter of each semicircular portion 21 in the welding path may also be consistent.By arranging the straight portions 22 in parallel with each other, the diameter of the semicircular portion 21 in the welding path 2 on the surface of the bus bar can reach the maximum, so that in the welding process, the laser beam can make a turn more easily without delay or a smooth turn is possible with a least delay, so that the variance of the welding energy value at each location of the welding path 2 is minimum and the distribution of the welding energy at all locations of the welding path 2 is more uniform, thus effectively preventing the situation of over welding in the bending of the welding path 2.In some embodiments of the present application, the welding path 2 extends along the radial direction of the busbar.It will be understood that the radial extent of the weld path 2 along the busbar may be a connection along the diameter direction of the busbar, or it may be offset by a certain angle relative to the diameter direction of the busbar, such that one end of the weld path 2 faces the centre of the busbar and the other end of the weld path 2 faces the edge of the busbar.By running a plurality of welding paths 2 along the radial direction of the bus bar, the number of connection layers between the bus bar and the tab on the winding package 3 becomes larger, so that the connection strength between the bus bar and the winding package 3 after welding and the flow cross section between the bus bar and the winding package 3 are simultaneously larger, thus improving the overall over-current effect of the battery.In some embodiments of the present application, the welding path 2 is provided in a plurality, and the individual welding paths 2 are arranged around the center of the bus bar.As long as the number of the welding paths 2 which are distributed circumferentially in a matrix-like manner around the busbar can meet the requirements for the welding strength and the flow cross section between the busbar and the winding package 3, it can generally be set to eight. A number more than eight decreases the welding efficiency, a number less than eight can easily result in the decrease of the welding strength, the reason why the welding sheet 2 is set to a multiple is to reduce the welding time between the bus bar and the winding package 3 in the battery.It is understood that the distance between the adjacent weld tracks 2 should be consistent in the matrix-like arrangement of the individual weld tracks 2 around the busbar in order to ensure that the overall weld strength and the overall flow cross section between the entire busbar and the winding package 3 are high.By distributing the welding paths 2 circumferentially and in a matrix-like manner around the busbar, the welding time can be significantly reduced, while ensuring the sufficiently strong welding strength and the sufficiently large flow cross section between the winding package and the busbar between the busbar and the winding package 3 in order to improve the efficiency of the entire welding process and thus to improve the efficiency of the entire battery production process.In some embodiments of the present application, the bus bar may be a positive or negative bus bar, and the embodiment of the present application is not limited thereto. In some embodiments, the busbar may be a positive busbar, and the positive busbar includes a round busbar body 11 and a lead-out tab 12 led out from the busbar body 11.It should be noted that the shapes of the positive and negative bus bars may be different, the positive bus bar includes a body 11 and a tab 12, but the weld tracks on the positive and negative bus bars must meet the requirements of freedom from inflection point and overlapping point.In some embodiments of the present application, as shown in FIG. 6 showing a third schematic structural view of the negative busbar according to an embodiment of the present application, the welding path 2 has an annular closed wave-shaped curve disposed around the center of the busbar.The welding path 2 may also be an annularly closed welding path 2 around the center of the busbar, which may also result in the welding path 2 avoiding the inflection point and the overlapping point, which cause the welding energy of the inflection point and the overlapping point on the welding path 2 to be too high, resulting in the situation of over welding, thus avoiding destruction of the welding strength between the winding package 3 and the busbar and reducing the flow cross section between the winding package 3 and the busbar. It should be noted that this is only an example of another embodiment of the curve without an inflection point and without an overlap point.In some embodiments, the busbar is a copper sheet. The busbar can be formed such that a coating is provided on the copper sheet, wherein the coating can be a chemical coating.In some embodiments of the present application, by forming the bus bar as a copper sheet, it is achieved that the internal resistance of the bus bar can be reduced and the heating state in the process of working the bus bar can be reduced, so that the power loss of the bus bar and the winding package can be reduced and the overall conductivity of the battery can be improved.The thickness of the bus bar may be determined according to actual need, and the embodiment of the present application does not limit this. In some embodiments of the present application, the thickness of the busbar is 0.1 to 0.5 mm, and further, it may be 0.15 to 0.25 mm, for example, it is 0.15 mm, 0.20 mm, 0.25 mm, etc.In some embodiments of the present application, it can be ensured that, in the welding, through welding of the bus bar or the winding package 3 can be avoided by setting the thickness of the bus bar to 0.1 to 0.5 mm.In some embodiments of the present application, the welding path 2 is a laser welding path so that the laser beam can laser weld the busbar and the winding package 3 along the welding path 2.By using laser welding for the welding path in the embodiment of the present application, the welding quality can be increased.In the second aspect, the application provides a battery as shown in FIG. 7, which is a schematic sectional view of a battery of an embodiment of the present application. The battery includes a winding package 3 and a bus bar, the welding side of the bus bar and the tab of the winding package 3 are welded.The orthographic projection of the welding sheet 2 on the bus bar on the welding side overlaps with the tab. The battery has all the advantageous effects that the busbar has due to the presence of the busbar. Since the welding path between the busbar and the winding package 3 has no inflection points or overlap, the welding energy at the inflection point can be reduced. The through welding of the bus bar can be avoided, and the use of the spiral welding in the related technology can be avoided in which a plurality of overlapping points are generated on the bus bar, in which case excessive welding energy is generated at the overlapping points on the bus bar, and then a plurality of welding paths 2 are arranged uniformly and in a matrix manner on the bus bar. This can reinforce the connection between the busbar and the winding package 3 and increase the flow cross section and at the same time improve the over-welding situation and improve the welding quality.In some embodiments, as shown in FIG. 8 showing a schematic structural view of a tab according to an embodiment of the present application, the winding package 3 is formed by winding a first electrode, a second electrode, and an intermediate release film around a winding shaft as a center, and the winding package 3 has a core and a circumferential surface; wherein along the winding axis the first electrode comprises a coated active agent portion and an uncoated portion, wherein at least a part of the uncoated portion is used as a tab, the uncoated portion comprises a first part A adjoining the core of the winding package 3, a second part B adjoining the circumferential surface of the winding package 3 and a third part C arranged between the first part A and the second part B, wherein along the winding axis the height of the first part A and / or the second part B is lower than the height of the third part C; wherein the third part C is divided into a plurality of segments 31 which can be bent separately and the plurality of segments 31 form a bending surface when bent along the radial direction of the core 3; wherein the bending surface is the tab of the winding package 3, and it is understood that the first part A and the second part B may also be divided; wherein along the direction from the core toward the circumferential surface, the bending surface includes a uniform layer number region and a decreasing layer number region, the number of layers of the segments 31 is uniform in the uniform layer number region, the decreasing layer number region is located on the circumferential side of the uniform layer number region, and the number of layers of the segments 31 decreases in the decreasing layer number region toward the circumferential side.It is understood that along the winding axis the second electrode also comprises a coated active agent portion and an uncoated portion, wherein at least a part of the uncoated portion is used as a tab, the uncoated portion comprises a first part A adjoining the core of the winding package 3, a second part B adjoining the circumferential surface of the winding package 3 and a third part C arranged between the first part A and the second part B, wherein along the winding axis the height of the first part A and / or the second part B is lower than the height of the third part C; wherein the third part C is divided into a plurality of segments 31 which can be bent separately, and the plurality of segments 31 form a bending surface when bent along the radial direction of the core 3; wherein the bending surface is the tab of the winding package 3; and it is understood that the first part A and the second part B can also be divided; wherein along the direction from the core toward the circumferential surface, the bending surface comprises a uniform layer number region and a decreasing layer number region, wherein the number of layers of the segments 31 is uniform in the uniform layer number region, wherein the decreasing layer number region is on the circumferential side of the uniform layer number region, and the number of layers of the segments 31 in the decreasing layer number region decreases toward the circumferential side.In some embodiments, the number of layers of the segments 31 in the uniform layer number region is more than 10.It is understood that the range in which the number of segments 31 reaches more than 10 can be set as a welding target range.In some embodiments, the projected area of the welding web 2 onto the bending surface lies entirely in the range of uniform layer number.It is understood that the uniform layer number region is the region having the largest number of layers in the bending surface, so that when the busbar is welded to the tab of the winding package 3, a tab layer formed by stacking a plurality of tabs of the winding package 3 can be avoided.In some embodiments, the width of the weld path 2 is greater than the width of the segment 31.In this way, it can be ensured that the welding track 2 must be able to be successfully welded to the adjacent two lugs of the same circle.In some embodiments, along the radial direction of the winding package, the welding web 2 is at least partially welded to two adjacent segments 31 in the same circle.In this way, it can be ensured that the welding track 2 must be able to be successfully welded to the adjacent two lugs of the same circle.As shown in FIG. 7, the welding side of the bus bar is welded to the tab of the winding package 3, the positive tab of the winding package 3 is made of aluminum foil and the negative tab is made of copper foil.Reference Number:11. Busbar body; 12th lead-out tab; 2nd welding track; 21st semicircular section; 22th straight section; 3rd winding package; 31, segment; A, first part; B, second part; C, third part.

Claims

A busbar comprising a welding side and a rear side arranged opposite each other, wherein the welding side is configured for welding with a winding package (3), the rear side is provided with a welding path (2) and the welding path (2) has a smooth wave-shaped curve.The busbar according to claim 1, wherein the welding path (2) includes a plurality of semicircular portions (21) and a plurality of straight portions (22), and the plurality of semicircular portions (21) and the plurality of straight portions (22) are alternately arranged and connected to each other.The busbar according to claim 2, wherein the plurality of straight portions (22) are arranged parallel to each other and spaced apart from each other, the welding path (2) extends along a radial direction of the busbar, the welding path (2) is provided in a plurality, and the individual welding paths (2) are arranged around a center of the busbar.The bus bar according to any one of claims 1 to 3, wherein the bus bar is a positive bus bar, and the positive bus bar includes a bus bar body (11) and a lead-out tab (12) led out from the bus bar body (11).The busbar according to any one of claims 1 to 2, wherein the welding path (2) has an annularly closed wave curve which is arranged around a center of the busbar.The busbar according to any one of claims 1 to 5, wherein a thickness of the busbar is 0.1 to 0.5 mm.A battery comprising a winding package (3) and a busbar according to any one of claims 1 to 6, wherein the welding side of the busbar and the tab of the winding package (3) are welded, wherein the orthogonal projection of the welding path (2) on the busbar onto the welding side overlaps with the tab.The battery according to claim 7, wherein the winding package (3) is formed by winding a first electrode, a second electrode, and an intermediate release film around a winding shaft as a center, and the winding package (3) has a core and a circumferential surface; wherein along the winding axis the first electrode comprises a coated active agent portion and an uncoated portion, wherein at least a part of the uncoated portion is used as a tab, the uncoated portion comprises a first part (A) adjoining the core of the winding package (3), a second part (B) adjoining the circumferential surface of the winding package (3) and a third part (C) arranged between the first part (A) and the second part (B), wherein along the winding axis a height of the first part (A) and / or the second part (B) is lower than a height of the third part (C); wherein the third part (C) is divided into a plurality of segments (31) which can be bent separately, and the plurality of segments (31) form a bending surface when bent along the radial direction of the core (3); the bending surface being the tab of the winding package (3); wherein along the direction from the core toward the circumferential surface, the bending surface comprises a uniform layer number region and a decreasing layer number region, the number of layers of the segments (31) being uniform in the uniform layer number region, the decreasing layer number region being on the circumferential side of the uniform layer number region, and the number of layers of the segments (31) decreasing in the decreasing layer number region toward the circumferential side.The battery according to claim 8, wherein the number of layers of the segments (31) in the uniform layer number range is more than 10.Battery according to claim 8 or 9, wherein the projection surface of the welding web (2) onto the bending surface is completely in the area of uniform layer number, wherein a width of the welding web (2) is greater than a width of the segment (31), wherein along the radial direction of the winding package the welding web (2) is at least partially welded to two adjacent segments (31) in the same circle.

Images