Busbar, battery module and battery pack

Abstract

A busbar configured to connect a plurality of cells (1) in series and / or parallel, characterized in that it comprises at least two conductive sheets (2), each conductive sheet (2) comprising a positive electrode weld (21) and a negative electrode weld (22); wherein a first weak part (230) is provided at a connection point of the positive electrode welds (21) of two adjacent conductive sheets (2) and a second weak part (240) is provided at a connection point of the positive electrode weld (21) and the negative electrode weld (22) of each of the conductive sheets (2); between each of the conductive sheets (2) the positive electrode weld (21) is connected to a positive electrode (11) of the cell (1) and the negative electrode weld (22) is connected to a negative electrode (12) of an adjacent cell (1);and between each of the cells (1) a pressure relief valve (13) is provided at its positive electrode (11), the positive electrode (11) and the pressure relief valve (13) are formed as a single unit, the pressure relief valve (13) is provided with a dilution region (131) configured to rupture upon pressure relief, the first weak part (230) and the second weak part (240) each being arranged above the dilution region (131) such that at least one of the following conditions is met: (a) the first weak part (230) and the second weak part (240) are ruptured by a strong impact force when the dilution region (131) ruptures, and (b) the first weak part (230) and the second weak part (240) fuse together by overcurrent when subjected to a strong current.

Description

Technical FieldThe present disclosure relates to the technical field of accumulators, and more particularly to a bus bar, an accumulator module, and an accumulator pack.Prior ArtTo improve the output voltage or output current of a cylindrical battery, one or more cells are typically connected in series and / or in parallel to form a battery module using a bus bar. For this purpose, the bus bar can transmit the power generated by all cells to the output port of the battery module in order to be able to be used by external devices. In addition, the bus bar may balance the differences in performance between the cells to improve the life and performance of the entire battery module.In the cylindrical battery module, the pressure relief valve of the cell is located on the same side as the positive and negative electrodes. The bus bar connects the positive and negative electrodes of the plurality of cells in series and in parallel by welding.Disclosure of Utility ModelThere is a technical defect in the above structural construction: the bus bar deteriorates the pressure relief efficiency of the pressure relief valve when the pressure needs to be relieved by the pressure relief valve, resulting in a slower pressure relief efficiency of the pressure relief valve. When a large amount of heat is released in the cells, the heat in the cells under this structure cannot be quickly dissipated, resulting in a continuous thermal runaway reaction caused by a rapid increase in the heat of the surrounding cells and damaging the entire battery module. In addition, the construction of the bus bar under this structure cannot provide timely and effective short circuit protection when the cells are short circuited.In a first aspect, in the present disclosure, there is provided a bus bar configured to connect a plurality of cells in series and / or in parallel, including at least two conductive sheets, and each conductive sheet including a positive electrode welding part and a negative electrode welding part.A first weak part is provided at a joint of the positive electrode, the parts of two adjacent conductive sheets are welded, and a second weak part is provided at a joint of the positive electrode welding part and the negative electrode welding part of each of the conductive sheets.Between each of the conductive sheets, the positive electrode welding part is connected to the positive electrode of the cell, and the negative electrode welding part is connected to the negative electrode of an adjacent cell.A pressure relief valve is provided between each of the cells at the positive electrode thereof, the positive electrode and the pressure relief valve being integrally formed, the pressure relief valve being provided with a thinning region configured to break upon pressure relief, the first weak part and the second weak part are respectively disposed over the thinning region so that at least one of the following conditions is satisfied: (a) the first weak part and the second weak part are broken by a strong impact force when the thinning region breaks, and (b) the first weak part and the second weak part are fused by overcurrent when subjected to a strong current.In a second aspect, in the present disclosure, there is provided a battery module including a plurality of cells and the bus bar, and the bus bar is connected to the conductive sheet in series and / or in parallel.In a third aspect, the present disclosure provides a battery pack including the battery module.(1) By locating the first and second weak portions of the bus bar over the dilution region, the dilution region is first opened by the high pressure gas in the cell when the pressure is relieved by the pressure relief valve. At the same time, the strong impact force of the quick-opening pressure relief valve breaks the first and second weak parts, whereby the pressure relief valve can efficiently release the pressure without being obstructed by the bus bar. When the first and second weak portions are broken, the circuit connection between the two adjacent cells is also disconnected, so that even if the cells are short-circuited, the short-circuit protection can be performed in time and, finally, double protection by internal pressure relief protection and cell short-circuit protection is achieved simultaneously when the cells do not function normally, which provides an improved guarantee for the thermal and electrical safety operation of the battery. Moreover, the first and second weak portions may also fuse by over-current when exposed to a strong current, whereby the purpose of double protection can also be achieved, i.e. protection against internal overpressure and protection against short circuits between cells when the cells are not normal.(2) The battery module provided in this disclosure is provided with the above-mentioned bus bar. By aligning the first and second weak points of the bus bar directly with the dilution region, the pressure relief valve can efficiently relieve the pressure and also disconnect the circuit connection loop between two adjacent cells, so that even in the event of a short circuit between cells or in the battery module, the short circuit protection can be performed in time and, finally, a double protection of the internal pressure relief protection of the battery module and the cell short circuit protection of the battery module can be achieved simultaneously to improve the thermal safety and the safety operating electrical performance of the battery module. Moreover, the first and second weak portions may also fuse by overcurrent when exposed to a strong current, whereby the double protection of the pressure relief protector and the short circuit protector may also be achieved.(3) The battery pack provided in this disclosure is provided with the above-mentioned battery module that can ensure that the pressure relief valve can effectively relieve the pressure and also disconnect the circuit connection loop between two adjacent cells, so that even in the event of a short circuit between the cells or in the battery module or the battery pack, short circuit protection can be performed in time and, finally, double protection of the internal pressure relief protection of the battery pack and the short circuit protection of the battery pack can be achieved simultaneously to improve the thermal safety and the safety operating electrical performance of the battery pack. Moreover, the first and second weak portions may also fuse by overcurrent, whereby the double protection of the pressure relief protector and the short circuit protector may also be achieved.Brief Description of the DrawingsFIG. 1 is a schematic structural diagram of the bus bar of the present disclosure in a front view; FIG. 2 is a schematic structural diagram of the bus bar of the present disclosure in a perspective view; FIG. 3 is a schematic structural diagram at A of FIG. 2 in a partial enlarged view; FIG. 4 is a schematic structural diagram of the bus bar of the present disclosure in a front view when the first weak parts and the second weak parts are both separated; FIG. 5 is a schematic structural diagram of the bus bar of the present disclosure in a perspective view when the first weak parts and the second weak parts are both separated; FIG. 6 is a schematic structural diagram of the cell of the present disclosure; FIG. 7 is a schematic structural diagram of the bus bar of the present disclosure in a front view connecting a plurality of cells in series and in parallel; FIG. 8 is a schematic structural diagram of the bus bar of the present disclosure in a perspective view connecting a plurality of cells in series and in parallel; FIG. 9 is a schematic structural diagram of the battery module of the present disclosure in a front view when the first weak parts and the second weak parts are partially separated; FIG. 10 is a schematic structural diagram of the battery module of the present disclosure in a perspective view when the first weak parts and the second weak parts are partially separated;The meaning of the attached labels is as follows:1 Cell, 11 positive electrode, 12 negative electrode, 13 pressure relief valve, 131 dilution region;2 conductive sheets, 21 positive electrode welding part, 210 positioning through hole, 22 negative electrode welding part, 220 arc-shaped surface;23 first connecting strip, 230 first weak part, 2301 first recess, 2302 first fragile part;24 second connecting strip, 240 second weak part, 2401 second recess, 2402 second fragile part;25 Buffer stage, 250 upper step surface, 251 lower step surface, 252 slope; and26 Positioning hole for processing.Embodiment(s)Referring to FIGS. 1 and 2 disclosed in the present disclosure, a bus bar configured to connect a plurality of cells 1 in series and / or in parallel is disclosed, whereby the plurality of cells 1 as a battery module can be connected in series and / or in parallel as illustrated in FIGS. 7 and 8. The bus bar may transmit all the power generated by the cells 1 to the output terminal of the battery module to be used by external devices.In an embodiment, as shown in FIG. 6, each of the cells 1 is a cylindrical power cell, and each of the cells 1 is provided with a positive electrode 11, a negative electrode 12, and a pressure relief valve 13. The positive electrode 11, the negative electrode 12, and the pressure relief valve 13 on each of the cells 1 are all located on the same end surface of the cell 1 to facilitate the connection of the plurality of cells 1 in series and in parallel via the bus bar. Specifically, the positive electrode 11 of the cell 1 is a positive electrode column, the pressure relief valve 13 is disposed around a periphery of the positive electrode 11, the negative electrode 12 is disposed around a periphery of the pressure relief valve 13. The positive electrode 11, the negative electrode 12 and the pressure relief valve 13 of the cell 1 are all arranged coaxially. Since the positive electrode 11 of each of the cells 1 is the positive electrode column, an upper surface of the positive electrode column is higher than the negative electrode 12 of each of the cells 1 and an upper surface of the pressure relief valve 13. such a height difference facilitates connection of the positive electrode column to the negative electrode 12 via the bus bar and is unlikely to result in a short circuit of the positive and negative electrode connection in the cell 1. When the cell 1 is a prismatic cell or a rectangular cell, the pressure relief valve 13 may be provided on the positive electrode 11 without being restricted by a position of the negative electrode 12. In some implementations, the pressure relief valve 13 may be a pressure relief device such as a safety valve, a pressure relief valve, or an explosion-proof valve.As illustrated in FIG. 6, the positive electrode 11 and the pressure relief valve 13 of the cell 1 are designed to be provided together. The positive electrode 11 and the pressure relief valve 13 of the cell 1 may be an integral structure or an integral molded structure. When the pressure relief valve 13 is opened, the pressure relief valve 13 falls off the cell 1, and the positive electrode 11 falls off as the pressure relief valve 13 falls off. When the internal pressure of the cell 1 reaches a preset maximum pressure at which a pressure relief valve 13 is opened, the pressure relief valve 13 is provided with a dilution portion 131 configured to be able to rupture pressure relief during pressure relief, and the dilution portion 131 is formed annularly, and the dilution portion 131 is provided near the negative electrode 12 to maximize an opening area of the pressure relief valve 13, facilitate rapid pressure relief, and improve safety performance. The dilution portion 131 is a pressure relief recess of the pressure relief valve 13, and the pressure relief recess is broken when a preset pressure is reached or exceeded. The pressure relief cavity may be a groove, cut, line of weakness, or other shape of the structure. The depth, width and shape of the pressure relief groove may be determined depending on the actual situation as long as it is ensured that the pressure relief groove breaks at the preset pressure. In some implementations, the positive electrode 11 may not fall out of the cell 1 when the pressure relief valve 13 is opened. In such a case, an additional ring is required for the dilution portion 131 of the pressure relief valve 13, and the additional dilution portion 131 needs to be located near the positive electrode 11 in order to interrupt both dilution portions 131 of the pressure relief valve 13 when the pressure relief valve 13 is opened.The pressure relief valve 13 of the cell 1 is directly connected to the positive electrode 11 of the cell 1. On the one hand, it is ensured that the pressure relief valve 13 can react quickly and precisely if the internal pressure of the cell 1 rises unusually sharply. This real-time reaction capability makes it easier to exhaust the gas accumulated in cell 1 in time, thereby preventing cell 1 from becoming dangerous due to excessive pressure. On the other hand, since the positive electrode 11 is one of the main portions of heat generation inside the cell 1, the construction of the pressure relief valve 13 provided on the positive electrode 11 of the cell 1 can more effectively utilize the heat dissipation performance of the pressure relief valve 13 to lower the temperature of the battery and improve the thermal stability of the battery. Thirdly, by integrating the pressure relief valve 13 with the positive electrode 11 of the cell 1, space in the cell 1 can be saved, resulting in a more compact structure of the battery, resulting in an increase in the energy density and power density of the battery while reducing the production cost. Fourth, by configuring the pressure relief valve 13 with the positive electrode 11 of the cell 1, the battery manufacturing process can be simplified and the associated production difficulties can be reduced. Therefore, the pressure relief valve 13 of the cell 1 is directly connected to the positive electrode 11 of the cell 1, which not only improves the safety and stability of the battery but also serves the purpose of compacting the battery structure and simplifying the manufacturing process.Referring to FIGS. 1 and 2, the bus bar in the present disclosure includes at least two conductive sheets 2, each of the conductive sheets 2 including a positive electrode welding part 21 and a negative electrode welding part 22, a first weak part 230 is provided at a joint of the positive electrode welding parts 21 of two adjacent conductive sheets 2, and a second weak part 240 is provided at a joint of the positive electrode welding part 21 and the negative electrode welding part 22 of each of the conductive sheets 2. Referring to FIGS. 7 and 8, the positive electrode welding part 21 of each of the conductive sheets 2 is connected to the positive electrode 11 of one of the cells 1, and the negative electrode welding part 22 is connected to the negative electrode 12 of another adjacent cell 1, thereby achieving series connection of the two adjacent cells 1; the positive electrode welding parts 21 of the two adjacent conductive sheets 2 are respectively connected to the positive electrode 11 of the two adjacent cells 1, thereby achieving parallel connection of the two adjacent cells 1. That is, each of the conductive sheets 2 establishes the series connection of two adjacent cells 1 and forms a unit cell. The two adjacent cells are connected in parallel via the positive electrode welded parts 21 of the two adjacent conductive sheets 2. The two adjacent cell units are arranged offset to allow for a more compact arrangement of the cells 1 so that more cells 1 can be arranged within a unit volume, thereby forming a low volume, high capacity battery module or pack. Specifically, the connection between the positive electrode welding part 21 and the positive electrode 11 and the connection between the negative electrode welding part 22 and the negative electrode 12 may be made by laser welding or by crimping or screwing.Since the positive electrode 11 of the cell 1 and the pressure relief valve 13 are designed to be assembled, the bus bar prevents the pressure relief valve 13 from opening when the bus bar is welded to the positive electrode 11 of the cell 1. The present design provides a bus bar avoidance saving to avoid the position of the pressure relief valve, but the area remaining for the pressure relief valve on the cell end face is very limited, resulting in a relatively small opening of the pressure relief valve, whereby pressure relief is not done fast enough. The adjustment of the prevention saving also reduces the connection area between the bus bar and the positive electrode, leading to a decrease in connection strength. To this end, when the positive electrode 11 of the cell 1 and the pressure relief valve 13 are constructed to cooperate with each other, the pressure relief valve 13 may break the first weak part 230 and the second weak part 240 when the pressure through the pressure relief valve 1 is aligned with the first weak part 230 and the second weak part 240 and the first weak part 230 and the second weak part 240 are directly aligned with the dilution region 131, as illustrated in FIGS. 7 and 8, to ensure that the pressure relief valve 13 can efficiently relieve the pressure without being obstructed by the bus bar.In some implementations, the dilution region 131 is first opened by the high pressure gas in the cells 1 by aligning the first weak part 230 and the second weak part 240 of the bus bar directly with the dilution region 131 when the pressure is released by the pressure relief valve 13, and the impact force of rapidly opening the pressure relief valve 13 breaks the first weak part 230 and the second weak part 240 (see FIGS. 4, 5, 9, and 10 ), so that the pressure relief valve 13 can efficiently release the pressure without being obstructed by the bus bar. In addition, as illustrated in FIGS. 9 and 10, the first weak part 230 and the second weak part 240 are broken, whereby the circuit connection between the two adjacent cells 1 is also broken, so that even if a short circuit occurs in the cell 1, the short circuit protection can be performed in time. Finally, the double protection of the internal pressure relief protection and of the cell short circuit protection is simultaneously achieved when the cells 1 are not normal, which provides an improved guarantee for the thermal and electrical safety operation of the battery. Moreover, the first weak part 230 and the second weak part 240 may also fuse by overcurrent when exposed to a strong current, whereby the purpose of double protection, i.e., protection of internal pressure relief and short-circuit protection between the cells 1, may also be achieved when the cells 1 are not normal.Since the first weak part 230 and the second weak part 240 may fuse by overcurrent when exposed to a strong current, there are two fuse conditions. The first fuse condition is that, since the first weak part 230 reaches two parallel-connected cells 1, in a short circuit or a thermal runaway inside the cells 1 or in a short circuit or a collision outside the cells 1, the first weak part 230 is burned to prevent the short circuit from spreading to the parallel-connected cells 1 to prevent the thermal runaway from spreading to the adjacent cells 1. The second fuse condition is that since the second weak part 240 reaches two series-connected cells 1, when a short circuit or a collision outside the battery module made of cells 1 results in a short circuit inside the battery module, the second weak part 240 is fused to prevent the short circuit from spreading to the series-connected cells 1 to prevent thermal runaway from spreading to the adjacent cells 1.When an abnormality occurs in a battery, for example, due to an external impact, a general short circuit and an internal thermal runaway of the battery may occur simultaneously. Therefore, the double protection achieved in the present disclosure simultaneously by the internal pressure relief protection and the cell short-circuit protection can effectively improve the safe operation of the battery. Additionally, the first weak portion 230 and the second weak portion 240 are incorporated into the present disclosure to be interrupted by the opened pressure relief valve 13 to achieve short circuit protection of the circuit that is faster and less time consuming than a fuse and therefore safer.In some implementations, as illustrated in FIGS. 9 and 10, since the positive electrode 11 and the pressure relief valve 13 of the cell 1 form an integral structure, the pressure relief valve 13 is disposed around the periphery of the positive electrode 11, and the dilution portion 131 of the pressure relief valve 13 is located near the negative electrode 12.In some implementations, when the pressure relief valve 13 is not normally opened or needs to be opened or the pressure is low after the pressure relief valve 13 is opened, i.e., the first weak part 230 and the second weak part 240 are not broken, the first weak part 230 and the second weak part 240 may also be melted by the overloaded large current, thereby providing short-circuit protection between the cells 1 and preventing the propagation of thermal runaway.In some implementations, as illustrated in FIGS. 1 and 2, two first weak parts 230 are provided, the two first weak parts 230 are respectively close to the positive electrode welding parts 21 of the two adjacent conductive sheets 2, and the two first weak parts 230 directly face the thinning regions 131 of the two adjacent pressure relief valves 13, respectively. Two first weak parts 230 are adopted in the present disclosure, and the two first weak parts 230 directly face the dilution regions 131 of the two adjacent pressure relief valves 13. When one of the pressure relief valves 13 is opened, it can independently cut off the connection between the two adjacent conductive sheets 2 to ensure that the pressure relief valve 13 on each cell 1 can be smoothly opened to achieve efficient pressure relief, thereby also achieving short circuit protection on each cell 1. The adjustment of the two first weak parts 230 may break the first weak part 230 and the second weak part 240 on the corresponding conductive sheet 2 when one of the adjacent pressure relief valves 13 is opened, so that it may cut off the connection between the two adjacent conductive sheets 2 independently of each other, so that each of the conductive sheets 2 may drop from one end of the cell 1 together with the corresponding pressure relief valve 13 and the positive electrode 11. In some implementations, only a first weak part 230 may be provided as long as the first weak part 230 corresponding to the thinning region 131 of the pressure relief valve 13 can be easily broken by the opened pressure relief valve 13, but the first weak part 230 is set to one, the joining strength of the positive electrode welded parts 21 of the two adjacent conductive sheets 2 can be weakened, and the first weak part 230 can largely deform or even break when the battery is subjected to an external shock.In some implementations, the positive electrode welding parts 21 of the two adjacent conductive sheets 2 are joined by a first joining strip 23 to increase the joining strength, and the two first weak parts 230 are located on the first joining strip 23 and are respectively provided at two ends of the first joining strip 23. The first connection strip 23 can not only ensure the connection strength between the two adjacent conductive sheets 2, facilitate the transportation and installation of the bus bar, but also resist the external impact force to avoid the breakage of the first weak part 230. Moreover, the first connection strip 23 can also carry a high current in order to reduce electrical losses.In some implementations, referring to FIGS. 1 and 2, the first weak part 230 is a first connection sheet provided with a first recess 2301, and the first connection sheet is located at two ends of the first connection strip 23. The first connecting plate forms first fragile parts 2302 on two sides of the first recess 2301, and the sum of the cross-sectional areas of the two first fragile parts 2302 is not larger than the cross-sectional area of the first recess 2301.The first recess 2301 of the present disclosure is disposed to reduce the cross-sectional area of the first connection sheet, so that the first weak part 230 can be easily and quickly broken when the pressure relief valve 13 is opened. When the first recess 2301 is located at the center of the first connection plate, the first recess 2301 is a through hole, the first connection plate forms a first fragile part 2302 on two sides of the first recess 2301, and the cross-sectional area of the first fragile part 2302 is much smaller than the cross-sectional area of the first recess 2301. To ensure that the first fragile part 2302 can withstand the rated current when charging and discharging the cell 1, the width and thickness of the first fragile part 2302 can be made as small as possible so that the first fragile part 230 is more easily broken by the opened pressure relief valve 13.In some implementations, it must also be ensured that the first fragile part 2302 can withstand the rated current when charging and discharging the cell 1, and that the first fragile part 230 is more likely to be damaged by the impact force of the opening pressure relief valve 13. It is also necessary to ensure that the joining strength of the first weak part 230 during installation and transportation is sufficient. To this end, in the present disclosure, the width of the first fragile part is set to A, the width of the first connection sheet is set to B, and the ratio of A / B is in the range of 0.12 to 0.15. When the ratio of A / B is less than 0.12, the first weak part 230 may burn out due to its inability to withstand the rated current in charging and discharging the battery and may not satisfy the requirements for the connection strength, which may result in easy deformation or breakage during installation and transportation. If the ratio of A / B is greater than 0.15, the first weak part 230 satisfies the requirements for withstanding the rated current in charging and discharging the battery and the connection strength, but it causes the first weak part 230 to be less likely damaged by the impact force of the opening pressure relief valve 13 or to be less likely to burn out in the event of an over current, resulting in invalid double protection of the first weak part 230. For this reason, the ratio of A / B must be in a range of 0.12 to 0.15.In some implementations, the width of the first frangible portion 2302 is 0.7 mm and the tolerance is plus or minus 0.05 mm, i.e., the width of the first frangible portion 2302 is in a range from 0.65 mm to 0.75 mm. Accordingly, the width of the first joint sheet is 5 mm and the tolerance is plus or minus 0.05 mm, i.e., the width of the first joint sheet is in a range of 4.95 mm to 5.05 mm.In some implementations, referring to FIGS. 1 and 2, in a single conductive sheet, the positive electrode welding part 21 and the negative electrode welding part 22 are joined by a second joining strip 24, the second weak part 240 is provided on the second joining strip 24, and the second weak part 240 is located near the positive electrode welding part 21. When the cell 1 is subjected to its own expansion force or an external force, the second connection strip 24 can be deformed accordingly, preventing the second weak part 240 from breaking. The second connection strip 24 mainly serves for series connection of two adjacent cells 1, and the current to be transmitted is relatively large, so that the width of the second connection strip 24 is relatively large and the cross-sectional area is relatively large. The first connecting strip 23 serves mainly for parallel connection of two adjacent cells 1, and the current to be transmitted is relatively small, so that the width of the first connecting strip 23 is relatively narrow and the cross-sectional area is relatively small. For this purpose, the width of the second connecting strip 24 is wider than the width of the first connecting strip 23.In some implementations, the second weak part 240 is a second connection plate provided with a second recess 2401, and the second recess 2401 is also intended to reduce a cross-sectional area of the second connection plate. The second recess 2401 is located at the center of the second joint sheet, the second joint sheet forms second fragile parts 2402 on two sides of the second recess 2401, and a cross-sectional area of each of the second fragile parts 2402 is smaller than a cross-sectional area of the second recess 2401.The second recess 2401 of the present disclosure is disposed to reduce the cross-sectional area of the second connection sheet so that the second weak part 240 can be easily and quickly broken when the pressure relief valve 13 is opened. When the second recess 2401 is located at the center of the second connection plate, the second recess 2401 is a through hole, the second connection plate forms a second fragile part 2402 on two sides of the second recess 2401, and the cross-sectional area of the second fragile part 2402 is much smaller than the cross-sectional area of the second recess 2401, so that the second fragile part 240 is more easily broken by the opened pressure relief valve 13. In order to ensure that the second fragile part 2402 can withstand the rated current when charging and discharging the cell 1, the width and thickness of the second fragile part 2402 can be made as small as possible so that the second fragile part 240 is more easily broken by the opened pressure relief valve 13.In some implementations, it must also be ensured that the second fragile part 2402 can withstand the rated current when charging and discharging the cell 1, and that the second fragile part 240 is more likely to be damaged by the impact force of the opening pressure relief valve 13. It is also necessary to ensure that the joining strength of the second weak part 240 during installation and transportation is sufficient. To this end, in the present disclosure, a width of the second fragile part 2402 is set to C, a width of the second connection sheet is set to D, and a ratio of C / D is in a range of 0.073 to 0.077. In some implementations, the ratio may be 0.074, 0.075, and 0.076. When the ratio of C / D is less than 0.073, the second weak part 240 may burn out due to its inability to withstand the rated current in charging and discharging the battery and may not satisfy the requirements for the connection strength, which may lead to easy deformation or breakage during installation and transportation. If the ratio of C / D is greater than 0.077, the second weak part 240 satisfies the requirements for withstanding the rated current in charging and discharging the battery and the connection strength, but it makes the second weak part 240 less likely to be damaged by the impact force of the opening pressure relief valve 13 or less likely to burn out in the event of an overcurrent, resulting in invalid double protection of the second weak part 240. For this reason, the ratio of C / D must be in a range of 0.073 to 0.077.In some implementations, the width of the second frangible portion 2402 is 2.1 mm and the tolerance is plus or minus 0.05 mm, i.e., the width of the second frangible portion 2402 is in a range from 2.05 mm to 2.15 mm. Accordingly, the width of the second connecting plate is 28 mm and the tolerance is plus or minus 0.05 mm, i.e., the width of the second connecting plate is in a range from 27.95 mm to 28.05 mm.When a plurality of cells 1 are connected in series and in parallel in the bus bar to form a battery module, foam adhesive needs to be poured between adjacent cells 1 for foaming so that all cells 1 are connected to each other by foam adhesive. The second recess 2401 may be used as an adhesive leak hole, the adjacent cells 1 are bonded to each other by the foam adhesive injected from the adhesive leak hole, and the excess adhesive may also overflow from the adhesive leak hole to ensure the uniformity of the filled adhesive between the adjacent cells 1. In some implementations, the foam adhesive may also be another adhesive adhesive.In some implementations, referring to FIGS. 2 and 3, the second connection strip 24 is provided with a buffer step 25, wherein the positive electrode welding part 21 and the second weak part 240 are both located on an upper step surface 250 of the buffer step 25, the negative electrode welding part 22 is located on a lower step surface 251 of the buffer step 25, and in the vertical direction, the upper step surface 250 is located above the lower step surface 251. In cell 1 in which the positive and negative electrodes are on the same end face, there is some level difference between the upper surface of positive electrode 11 and the upper surface of negative electrode 12. In addition, the upper surface of the positive electrode 11 of the cell 1 is also higher than the upper surface of the pressure relief valve 13 of the cell 1, so that a gap is provided between the lower surface of the second weak part 240 and the upper surface of the corresponding pressure relief valve 13. When it is necessary to pour foam adhesive between adjacent cells 1 for foaming, the second recess 2401 serves as an adhesive leak hole. After the foam adhesive is injected from the second recess 2401, the foam adhesive can smoothly flow into the gap between the bottom surface of the second weak part 240 and the top surface of the corresponding pressure relief valve 13.In the present disclosure, a buffer stage 25 is provided. First, the buffer step 25 may compensate for the difference in height between the positive electrode 11 and the negative electrode 12 so that the positive electrode welding part 21 may be attached to the upper surface of the positive electrode 11 and the negative electrode welding part 22 may be attached to the upper surface of the negative electrode 12 to facilitate welding and fastening of the bus bar and the positive and negative electrodes; second, the buffer step 25 may buffer a slight relative movement between the two adjacent cells 1 to prevent pulling or breaking of the second weak part 240.In some implementations, the upper step surface 250 and the lower step surface 251 are connected by a slope 252, and the joints between the upper step surface 250, the lower step surface 251, and the slope 252 are all arc-shaped. Both the arcuate shape and the slope 252 provide greater buffer deformation for the buffer step 25, thereby permitting it to resist greater impact force or relative displacement. The height difference between the upper step surface 250 and the lower step surface 251 is in the range of 1 to 2 mm. In some implementations, the height difference is 1.5 mm.In some implementations, the second connection strip 24 is provided with a positioning hole 26 for processing between the buffer stage 25 and the second weak part 240. The positioning hole 26 for processing enables positioning of the bus bar during processing to achieve precise processing of the bus bar.In some implementations, referring to FIG. 6, the positive electrode 11, the negative electrode 12, and the pressure relief valve 13 of the cell 1 are all arranged coaxially, and the positive electrode 11 is provided in the middle, the outer side of the positive electrode 11 being surrounded sequentially by the pressure relief valve 13 and the negative electrode 12. That is, the positive electrode 11 is the electrode column, and the pressure relief valve 13 and the negative electrode 12 are rings surrounding the electrode column. Referring to FIGS. 1 and 2, the negative electrode welding part 22 is provided with a concave arc-shaped surface that cooperates with the annular surface of the negative electrode 12 and avoids interference with the pressure relief valve 13. In order to conform to the round electrode column of the positive electrode 11, the positive electrode welding part 21 is a round surface that cooperates with the round electrode column.The negative electrode welding part 22 of the present disclosure is provided with a concave arc-shaped surface 220. On the one hand, the concave arc-shaped surface 220 leads to an increase in the welding area with the negative electrode 12 and an improvement in the joining strength. On the other hand, the concave arc surface 220 prevents the pressure relief valve 13 from interfering and prevents the negative electrode welding part 22 from covering the thinning region 131 of the pressure relief valve 13, whereby the pressure relief valve 13 is not normally opened. The round surface of the positive electrode welding part 21 cooperates with the round electrode column of the positive electrode 11 to increase the joining area and increase the joining strength.In some implementations, see FIGS. 1 and 2, the positive electrode welding part 21 is provided with a positioning through hole 210 configured to be welded to the positive electrode 11 of the cell 1. When a robot performs laser welding work, the positive electrode 11 can be closed by the positioning through hole 210, so that the positive electrode welding part 21 can be welded to the positive electrode 11 accurately. The positive electrode 11 opposite to the positioning through hole 210 is provided with a groove for receiving soldering water, so that the connection between the positive electrode 11 and the positive electrode welding part 21 is more secure.The positioning through hole 210 of the present technical solution facilitates finding the positive electrode 11 when laser welding the positive electrode welding part 21 and the positive electrode 11, thereby achieving the accuracy of welding.In the present disclosure, there is also provided a battery module related to FIGS. 7 to 10 and including a plurality of cells 1 and an above-mentioned bus bar. The bus bar connects the plurality of cells 1 in series and / or in parallel by a plurality of conductive sheets 2, thereby forming a battery module.With respect to the battery module provided in the present disclosure, by appropriately setting the first weak part 230 and the second weak part 240 of the bus bar above the dilution region, the pressure relief valve 13 may break the first weak part 230 and the second weak part 240 when the pressure is released, so that the pressure relief valve 13 may efficiently release the pressure and the pressure relief valve 13 may also disconnect the circuit connection loop between two adjacent cells 1. Therefore, the short-circuit protection can be performed in good time even in the event of a short circuit between the cells 1 or inside and outside the battery module, and finally double protection of the internal pressure relief protection of the battery module and of the cell short-circuit protection of the battery module can be achieved simultaneously in order to improve the thermal safety and the electrical operating safety of the battery module. Moreover, the first weak part 230 and the second weak part 240 may also fuse by overcurrent when exposed to a strong current, whereby the double protection of the pressure relief protector and the short circuit protector may also be achieved.In some implementations, see FIGS. 7 and 8, the positive electrode welded parts 21 of the two adjacent conductive sheets 2 are respectively connected to the positive electrodes 11 of the two adjacent cells 1, so that the two adjacent cells 1 are connected in parallel. The positive electrode welding parts 21 and the negative electrode welding parts 22 of each conductive sheet 2 are respectively connected to the positive electrode 11 and the negative electrode 12 of the two adjacent cells 1, so that the two adjacent cells 1 are connected in series. That is, each of the conductive sheets 2 is connected in series to two adjacent cells 1 to form one cell unit, and the adjacent two cell units are connected by a positive electrode welding part 21 of the adjacent two conductive sheets 2 to achieve parallel connection of the adjacent two cell units. The two adjacent cells are arranged offset in order to allow a more compact arrangement of the cells 1, so that the battery module has the smallest possible volume at maximum capacity.When the battery module is assembled, foam adhesive must be poured between the adjacent cells 1 for foaming so that all the cells 1 are connected to each other by the foam adhesive. The second recess 2401 may be used as an adhesive leak hole, the adjacent cells 1 are bonded to each other by the foam adhesive injected from the adhesive leak hole, and the excess adhesive may also overflow from the adhesive leak hole to ensure the uniformity of the filled adhesive between the adjacent cells 1. In some implementations, the foam adhesive may also be another adhesive adhesive.In the present disclosure, a battery pack including the above-mentioned battery module is further provided.By aligning the first weak part 230 and the second weak part 240 of the bus bar directly with the dilution region 131, the dilution region 131 is first opened by the high pressure gas in the cell 1 when the pressure is released by the pressure relief valve 13. At the same time, the strong impact force of the quick-opening pressure relief valve 13 breaks the first weak part 230 and the second weak part 240. It ensures that the pressure relief valve 13 can effectively relieve the pressure and can also disconnect the circuit connection loop between two adjacent cells 1, so that even in the event of a short circuit between the cells 1 or in the battery module or in the battery pack, the short circuit protection can be carried out in good time and finally a double protection of the internal pressure relief protection of the battery pack and the short circuit protection of the battery pack can be achieved simultaneously in order to improve the thermal safety and the electrical safety operating performance of the battery pack. Moreover, the first weak part 230 and the second weak part 240 may also fuse by overcurrent, whereby the double protection of the pressure relief protector and the short circuit protector may also be achieved.The battery pack described in the present disclosure can be used in a variety of fields, for example in electric vehicles, electric bicycles, electric bicycles and other electric devices, in mobile devices such as smartphones, drones, aircraft models, as well as in energy storage systems such as mains energy storage, solar energy storage and even in industrial robots and medical devices.

Claims

A bus bar configured to connect a plurality of cells (1) in series and / or in parallel, characterized by comprising at least two conductive sheets (2), each conductive sheet (2) comprising a positive electrode welding part (21) and a negative electrode welding part (22); wherein a first weak part (230) is provided at a connection location of the positive electrode welding parts (21) of two adjacent conductive sheets (2) and a second weak part (240) is provided at a connection location of the positive electrode welding part (21) and the negative electrode welding part (22) of each of the conductive sheets (2); between each of the conductive sheets (2), the positive electrode welding part (21) is connected to a positive electrode (11) of the cell (1) and the negative electrode welding part (22) is connected to a negative electrode (12) of an adjacent cell (1); and between each of the cells (1), a pressure relief valve (13) is provided at the positive electrode (11) thereof, the positive electrode (11) and the pressure relief valve (13) are integrally formed, the pressure relief valve (13) is provided with a thinning portion (131) configured to break upon pressure relief, wherein the first weak part (230) and the second weak part (240) are respectively disposed over the thinning portion (131) so that at least one of the following conditions is satisfied: (a) the first weak part (230) and the second weak part (240) are broken by a strong impact force when the thinning portion (131) breaks, and (b) the first weak part (230) and the second weak part (240) are fused by overcurrent when subjected to a strong current.The bus bar according to claim 1, wherein the positive electrode welding part (21) and the negative electrode welding part (22) of each of the conductive sheets (2) are respectively connected to the positive electrode (11) and the negative electrode (12) of two adjacent cells (1) so that the two adjacent cells (1) are connected in series and form a cell unit that are connected in parallel to two adjacent cell units through the positive electrode welding parts (21) of the two conductive sheets (2) thereon, a first connection strip (23) is provided at a connection location of the positive electrode welding parts (21) of the two conductive sheets (2) on the two adjacent cell units, and the first weak part (230) is provided on the first connection strip (23).The bus bar according to claim 2, wherein two first weak parts (230) are provided, the two first weak parts (230) are respectively provided at two ends of the first connection strip (23) and near the corresponding positive electrode welding part (21), and the two first weak parts (230) are respectively directly facing the thinning regions (131) of the two adjacent pressure relief valves (13).The bus bar according to any one of claims 1-3, wherein the first weak part (230) is a connection plate provided with a first recess (2301).The bus bar according to claim 4, wherein the first recess (2301) is disposed at the center of the connection sheet.The bus bar according to claim 4, wherein the connection plate forms fragile parts on two sides of the first recess (2301), and the sum of the cross-sectional areas of the two fragile parts is not larger than the cross-sectional area of the first recess (2301).The bus bar according to claim 6, wherein a width of the fragile part is A, a width of the connection sheet is B, and a ratio of A / B is in a range of 0.12 to 0.15.The bus bar according to claim 1, wherein in a single conductive sheet, the positive electrode welding part (21) and the negative electrode welding part (22) are connected by a second connection strip (24), the second weak part (240) is provided on the second connection strip (24), and the second weak part (240) is close to the positive electrode welding part (21).The bus bar according to claim 1 or 8, wherein the second weak part (240) is a connection plate having a second recess (2401).The bus bar according to claim 9, wherein the second recess (2401) is disposed at the center of the connection plate, the connection plate forms fragile parts on two sides of the second recess (2401), and a cross-sectional area of each of the fragile parts is smaller than a cross-sectional area of the second recess (2401).The bus bar according to claim 10, wherein a width of the fragile part is C, a width of the connection sheet is D, and a ratio of C / D is in a range of 0.073 to 0.077.The bus bar according to claim 8, wherein the second connection strip (24) is provided with a buffer step (25), the positive electrode welding part (21) and the second weak part (240) are both located on an upper step surface (250) of the buffer step (25), the negative electrode welding part (22) is located on a lower step surface (251) of the buffer step (25), and the upper step surface (250) is connected to the lower step surface (251) by a slope (252).The bus bar according to claim 12, wherein a height difference between the upper step surface (250) and the lower step surface (251) is in the range of 1 to 2 mm.The bus bar according to claim 1 or 8, wherein the negative electrode (12) of the cell (1) is an annular surface, and the negative electrode welding part (22) is provided with a concave arc-shaped surface that cooperates with the annular surface, the positive electrode (11) of the cell (1) is a circular electrode column, and the positive electrode welding part (21) is a circular surface that cooperates with the circular electrode column.The bus bar according to any one of claims 1-3, wherein the positive electrode welding part (21) is provided with a positioning through hole (210) configured to be in welding connection with the positive electrode (11) of the cell (1).The bus bar of claim 1, wherein the pressure relief valve (13) is disposed around a periphery of the positive electrode (11), and the positive electrode (11) drops as the pressure relief valve (13) drops when the pressure is released.The bus bar according to claim 1 or 16, wherein the negative electrode (12) of the cell (1) is provided around a periphery of the pressure relief valve (11), and the dilution region (131) is provided near the negative electrode (12).A battery module comprising a plurality of cells (11) and the bus bar according to any one of claims 1-17, wherein the bus bar connects the plurality of cells (1) in series and / or in parallel via the conductive sheets (2).The battery module according to claim 18, wherein the positive electrode welding part (21) and the negative electrode welding part (22) of the conductive sheet (2) are respectively connected to the positive electrode (11) and the negative electrode (12) of the two adjacent cells (1) so that the two adjacent cells (1) are connected in series and form one cell unit; and the two adjacent cell units are connected by the positive electrode welding parts (21) of the two adjacent conductive sheets (2) to achieve parallel connection of the two adjacent cell units.The battery module according to claim 18, wherein the second recess (2401) is an adhesive leak hole, and the two adjacent cells (1) are connected to each other by viscous adhesive injected from the adhesive leak hole.A battery pack comprising a battery module according to any of claims 18-20.

Images