A cylindrical secondary cell lid comprising a petal vent feature

Abstract

This disclosure presents a cylindrical secondary cell lid (1) for a cylindrical secondary cell (100), the cylindrical secondary cell lid (1) comprising a groove pattern (10) that is configured to provide a vent opening in the cylindrical secondary cell lid (1) if a pressure to which the cylindrical secondary cell lid (1) is subjected reaches a threshold value. The groove pattern (10) defines a center portion (20), a first off-center portion (31), a second off-center portion (32), and a third off-center portion (33), wherein the off-center portions (31, 32, 33) extend from the center portion (20) and are respectively formed by two radial groove pattern sections (11a, 11b, 12a, 12b, 13a, 13b) and one circumferential groove pattern section (11c, 12c, 13c) that connects the two radial groove pattern sections (11a, 11b, 12a, 12b, 13a, 13b).

Description

[0001] A CYLINDRICAL SECONDARY CELL LID COMPRISING A PETAL VENT FEATURE

[0002] TECHNICAL FIELD

[0003] The present disclosure generally pertains to cylindrical secondary cells, and more precisely to a lid for such a cell.

[0004] BACKGROUND

[0005] In addressing climate change, there is an increasing demand for rechargeable batteries, e.g. to enable electrification of transportation and to supplement renewable energy. Currently, lithium-ion batteries are becoming increasingly popular. They represent a type of rechargeable battery in which lithium ions move from the negative electrode to the positive electrode during discharge and back when charging.

[0006] It is known in the art of battery manufacturing to provide an electrically conductive sheet with a coating that is rolled up into a cylinder. In so called tabless cells, the electrically conductive sheet has an uncoated edge protruding on an end side of the roll or cylinder. The edge may be folded to provide an electrical contact surface.

[0007] As the demand for rechargeable batteries increases, more and more focus is being placed on production speed and cost. To achieve an effective production of rechargeable batteries, the design of the batteries as well as their manufacturing process can be optimized.

[0008] Another aspect to consider is that the rechargeable batteries must be safe to use. Therefore, rechargeable batteries have at least one vent for releasing e.g. gas when the pressure inside the batteries rises above an allowed level.

[0009] SUMMARY

[0010] The present disclosure aims at providing improved secondary cells and parts thereof. The improvements may be in safety, manufacturing efficiency, use of materials and energy performance.

[0011] According to one aspect of the present disclosure, a cylindrical secondary cell lid for a cylindrical secondary cell is provided. The cylindrical secondary cell lid comprises a groove pattern that is configured to provide a vent opening in the cylindrical secondary cell lid if a pressure to which the cylindrical secondary cell lid is subjected reaches a threshold value. The groove pattern defines a center portion, a first off-center portion, a second off-center portion, and a third off-center portion. The off-center portions extend from the center portion and are respectively formed by two radial groove pattern sections and one circumferential groove pattern section that connects the two radial groove pattern sections. The present disclosure further provides a cylindrical secondary cell comprising such a cylindrical secondary cell lid.

[0012] Such a cylindrical secondary cell lid may provide safe venting, e.g. in the event of a so called thermal runaway. At the same time, an electrode roll arranged inside the cylindrical secondary cell may be stably supported between the off-center portions of the cylindrical secondary cell lid. The electrode roll may be attached to the cylindrical secondary cell lid between the off- center portions, while the off-center portions are not attached to the electrode roll to facilitate the groove pattern rupturing to provide the vent opening. Further, the electrode roll may be directly electrically connected to the cylindrical secondary cell lid between the off-center portions.

[0013] The present cylindrical secondary cell lid may thus support the electrode roll, form an electrical connection to the electrode roll, and also provide for safe venting of the cylindrical secondary cell. The size or area of the off-center portions in relation to the total cylindrical secondary cell lid area may be selected to optimise the area that is available for forming the vent opening versus the area for supporting the electrode roll.

[0014] According to a further aspect of the present disclosure, a battery system comprising a cylindrical secondary cell with the cylindrical secondary cell lid is provided. According to a further aspect, a vehicle comprising a cylindrical secondary cell with the cylindrical secondary cell lid is provided.

[0015] Additional conceivable features, and associated advantages, will become clear from the following description of embodiments and examples.

[0016] BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The embodiments disclosed herein are illustrated by way of example, and not by way of limitation, in the figures of the accompanying drawings. Like reference numerals refer to corresponding parts throughout the drawings, in which Figure 1 shows a cylindrical secondary cell lid in isometric view,

[0018] Figure 2 illustrates the lid of figure 1 in axial cross-section together with an end of an axial sidewall of a cylindrical secondary cell and an end of an electrode roll,

[0019] Figure 3 illustrates the cylindrical secondary cell and the lid of figures 1 and 2,

[0020] Figure 4 schematically illustrates a groove pattern configured to provide a vent opening in the cylindrical secondary cell lid of figures 1 to 3,

[0021] Figure 5 schematically illustrates an alternative groove pattern to the one of figure 4, Figure 6 shows an alternative cylindrical secondary cell lid,

[0022] Figure 7 illustrates the lid of figure 6 in axial cross-section,

[0023] Figures 8-13 shows further alternative cylindrical secondary cell lids in isometric views and axial cross-sections, and

[0024] Figures 14-15 are cross-sectional views of groove patterns of the cylindrical secondary lid.

[0025] DETAILED DESCRIPTION

[0026] Embodiments of the present disclosure will now be described more fully hereinafter. The invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those persons skilled in the art.

[0027] A rechargeable battery, often referred to as a secondary battery, typically comprises one or more secondary cells (herein referred to as "cells") electrically connected to each other. A cell having both terminals arranged at one end of the cell may bring advantages with regards to electrically connecting the cell to a load. Conductors electrically connecting the terminals to the load may then be positioned on the same end, the terminal end, of the cell. The opposite cell end may be dedicated to electrolyte filling and venting of gas and / or other ejecta, and may hence be referred to as the electrolyte-filling end of the cell.

[0028] An overpressure may be generated within the cell during operation, in particular upon malfunction of the cell or of the load connected to the cell. Such malfunction may require a pressure release action in which gas and / or other ejecta is discharged from the cell. It may be advantageous to direct the released gas and / or other ejecta away from the above-mentioned conductors. A plurality of cells may typically be positioned at a low position in an electric vehicle. The cells may be arranged with their terminal ends directed upwards and their electrolyte-filling ends directed downwards. Upon malfunction, for example resulting from a faulty electric vehicle charger, a vehicle malfunction or a faulty cell, a release of gas and / or other ejecta from the electrolyte-filling end(s) will be advantageously directed downwards towards the ground beneath the vehicle.

[0029] When both terminals of a cell are arranged at one end of the cell, ensuring electrical isolation between the conductors that electrically connect the terminals to the load is very important. One terminal (typically the negative terminal) may be formed by the enclosure of the cell, also referred to as the can. The other terminal (typically the positive terminal) may be formed by a terminal part that extends through a terminal hole in a can end wall. The terminal part may typically serve the dual purposes of proving an electrical terminal and sealing the can. Advantageously, as in the current examples, the terminal part may be provided in the form of a rivet. An electrical isolator is arranged between the terminal part and the can end wall.

[0030] This disclosure relates to a cell 100, more precisely a cylindrical cell 100, having both terminals arranged at one end (figure 3). However, the teachings herein, at least as regards the groove pattern, can also be applied to other cells, such as cells of other shapes and / or having the terminals arranged on different ends or sides of the cell.

[0031] Figure 1 shows a cylindrical secondary cell lid 1 for a cylindrical secondary cell 100. The cylindrical secondary cell lid 1 comprises a groove pattern 10 that is configured to provide a vent opening in the cylindrical secondary cell lid 1 if a pressure (overpressure) to which the cylindrical secondary cell lid 1 is subjected reaches a threshold value, as described above. In case of such an overpressure, the groove pattern 10 may party or entirety rupture.

[0032] The groove pattern 10 is also illustrated in figures 2 to 13, where figure 5 illustrates an alternative groove pattern. The groove pattern 10 of figures 1, 3, 4 to 6, 8, 10 and 12 defines a center portion 20, a first off-center portion 31, a second off-center portion 32 and a third off- center portion 33. The off-center portions 31, 32, 33 extend from the center portion 20.

[0033] By the term extend may be meant that the off-center portions 31, 32, 33 are continuous with the center portion 20. In other words, the off-center portions 31, 32, 33 and the center portion 20 are integral. Referring for example to figure 1, the off-center portions 31, 32, 33 and the center portion 20 may extend in the same plane (XY-plane). In the present example, the plane extends orthogonal to the longitudinal axis (Z) of the cell 100. Thus, the off-center portions 31, 32, 33 and the center portion 20 may be coplanar.

[0034] Should the entire groove pattern 10 rupture, the off-center portions 31, 32, 33 and the center portion 20 may be released from the secondary cell lid 1 in one piece. Should the entire groove pattern rupture 10, the off-center portions 31, 32, 33 and the center portion 20 may form a single vent opening in the secondary cell lid 1.

[0035] The off-center portions 31, 32, 33 and the center portion 20 can be said to jointly form an island on the cylindrical secondary cell lid 1. The off-center portions 31, 32, 33 may alternatively be referred to as tongues or half-islands.

[0036] The off-center portions 31, 32, 33 may, as is shown, be equidistantly distributed along the circumference of the secondary cell lid 1. Such a distribution may be beneficial for stably supporting the electrode roll 120.

[0037] Referring in particular to figures 4 and 5, the off-center portions 31, 32, 33 are respectively formed or defined by two radial groove pattern sections I la, 11b, 12a, 12b, 13a, 13b and one circumferential groove pattern section 11c, 12c, 13c that connects the two radial groove pattern sections I la, 11b, 12a, 12b, 13a, 13b.

[0038] In some detail, the first off-center portion 31 is formed by two first radial groove pattern sections I la, 11b and one first circumferential groove pattern section 11c that connects the two first radial groove pattern sections 1 la, 1 lb. The second off-center portion 32 is formed by two second radial groove pattern sections 12a, 12b and one second circumferential groove pattern section 12c that connects the two second radial groove pattern sections 12a, 12b. The third off- center portion 33 is formed by two third radial groove pattern sections 13a, 13b and one third circumferential groove pattern section 13c that connects the two third radial groove pattern sections 13 a, 13b.

[0039] Referring to figures 1, 3, 4, 6, 8, 10 and 12, the off-center portions 31, 32, 33 may essentially have the shape of three petals. Referring to figure 5, there may be a fourth off-center portion 34 and the off-center portions 31, 32, 33, 34 may essentially have the shape of four petals. As is shown in figures 1, 2 and 6 to 13, which show possible actual realizations of the secondary cell lid 1, the center portion 20 may be circular. In figure 4 the three petals are circumferentially equidistantly distributed and thus separated by 120 degrees. In figure 5 the four petals are circumferentially equidistantly distributed and thus separated by 90 degrees.

[0040] As in the present examples, the off-center portions 31, 32, 33 may have essentially the same extension or length as measured in the radial direction and in the circumferential direction. The off-center portions 31, 32, 33 may comprise a radially inner end that extends from the center portion 20 and a radially outer end that is located at approximately half the radius of the cylindrical secondary cell lid 1. In the present examples, the radially outer ends are of a circumferential extension that exceeds the circumferential extension of the radially inner ends.

[0041] Referring e.g. to figure 1, the radial groove pattern sections I la, 11b, 12a, 12b, 13a, 13b may extend in the radial direction. The radial groove pattern sections I la, 11b, 12a, 12b, 13a, 13b may be straight. The circumferential groove pattern sections 11c, 12c, 13c may extend in the circumferential direction. The circumferential groove pattern sections 11c, 12c, 13c may be curved, in the present examples circularly curved.

[0042] The transitions from the radial groove pattern sections to the circumferential groove pattern sections may be rounded, as is illustrated e.g. in figures 4 and 5. Also, the transitions from the radial groove pattern sections to the center portion 20 may be rounded. The groove pattern 10 may be described as undulating, or smoothly undulating, around the center of the secondary cell lid.

[0043] As is illustrated in figures 1 to 3, and 6 to 13, the cylindrical secondary cell lid 1 may comprise roll contact regions 41, 42, 43 arranged in-between the off-center portions 31, 32, 33. The roll contact regions 41, 42, 43 are thus separate from the off-center portions 31, 32, 33. Thus, the roll contact regions 41, 42, 43 and the off-center portions 31, 32, 33 do not overlap.

[0044] As is best understood from figures 2 and 3, the roll contact regions 41, 42, 43 are adapted to be arranged in direct electrical contact, or physical contact, with an electrode roll 120 that is arranged inside the cell 100. Thus, the cylindrical secondary cell lid 1 is configured to be arranged in direct electrical contact with the electrode roll 120. By providing roll contact regions 41, 42, 43 and also off-center portions 31, 32, 33, the cylindrical secondary cell lid 1 advantageously provides for both direct electrical contact with the electrode roll 120 and for the formation of a safe vent opening. Typically, the roll contact regions 41, 42, 43 are welded, e.g. laser welded, to the electrode roll 120. The areas of the roll contact regions 41, 42, 43 and the off-center portions 31, 32, 33 may, as is illustrated, correspond to one another. In other words, the total size of the off-center portions 31, 32, 33 may correspond to the total size of the roll contact regions 41, 42, 43. By corresponding sizes may be meant that the sizes are roughly the same. Thus, typically, the total size of the off-center portions 31, 32, 33 is not as large as ten times the total size of the roll contact regions 41, 42, 43. For example, the roll contact regions 41, 42, 43 may be of the same total area as the off-center portions 31, 32, 33, or the roll contact regions 41, 42, 43 may have a total area that is 150 percent or 200 percent the total area of the off-center portions 31, 32, 33, or vice versa.

[0045] The roll contact regions 41, 42, 43, which are provided for welding the cylindrical secondary cell lid 1 to the electrode roll 120, may be of a total area that corresponds 20 to 60 percent of the cylindrical secondary cell lid area. The area of the roll contact regions 41, 42, 43 may be referred to as a weld area. A weld area of 20 to 60 percent of the cylindrical secondary cell lid area may ensure a god electrical and mechanical connection to the electrode roll 120. For example, the roll contact regions 41, 42, 43 may be of a total area that corresponds 20 to 60 percent, or 30 to 50 percent, of the cylindrical secondary cell lid area.

[0046] In the present examples, apart from figure 5, the number of off-center portions 31, 32, 33 is three and the number of roll contact regions 41, 42, 43 is three. When the number of roll contact regions 41, 42, 43 is three, there is room for an appropriate number of weld lines on each roll contact region 41, 42, 43. Thereby, a good electrical contact between the cylindrical secondary cell lid 1 and the electrode roll 120 may be obtained, which ensured a low internal resistance.

[0047] Referring to figure 2, the present roll contact regions 41, 42, 43 are axially separated Z1 from the off-center portions 31, 32, 33 such that the roll contact regions 41, 42, 43 may be arranged in direct electrical contact with an electrode roll 120 arranged inside the cylindrical secondary cell 100 while the off-center portions 31, 32, 33 are arranged at a distance from the electrode roll 120. In the present examples, the roll contact regions 41, 42, 43 and the off-center portions 31, 32, 33 are not coplanar.

[0048] Thus, the roll contact regions 41, 42, 43 may be axially separated Z1 from the off-center portions 31, 32, 33, and also be separated from the off-center portions 31, 32, 33 as seen in a plan view. In other words, when the cylindrical secondary cell lid 1 is viewed from above or below, i.e. seen in an axial view, the roll contact regions 41, 42, 43 are separated from the off- center portions 31, 32, 33. The roll contact regions 41, 42, 43 may be adjacent the off-center portions 31, 32, 33, as seen in an axial view.

[0049] As is illustrated, the cylindrical secondary cell lid 1 may comprise an outer contact region 50, or circumferentially outer contact region or rim, which is adapted to be arranged in direct electrical contact with an axial sidewall 110 of the cylindrical enclosure of the cell 100. Referring to figures 2 and 3, the cylindrical secondary cell lid 1 may thus be configured to be arranged in direct electrical contact with the electrode roll 120 and also in direct electrical contact with the axial sidewall 110.

[0050] The outer contact region 50 of figures 1 to 3 and 6 to 9 comprises a flange 55 that is adapted to be arranged in direct electrical contact with the axial sidewall 110. Referring to figure 2, the outer contact region 50, more precisely its flange 55 is present, may be welded to the axial sidewall 110. The welding may be performed in a direction that is at least substantially aligned with the longitudinal axis (Z) of the cell 100. As is indicated to the left in figure 2, the welding may be aligned with the longitudinal axis of the cell 100. In other words, a laser that is used to accomplish the weld may be aligned with the longitudinal axis of the cell 100. The laser may be directed towards a free edge of the axial sidewall 110 that is brought in contact with a free edge of the cylindrical secondary cell lid 1. The weld may be visually inspected to ensure that a proper and tight seal is obtained.

[0051] In figures 10 to 13, the outer contact region 50 does not comprise any flange but is aligned with the radial direction. Instead, the axial sidewall 110 of the cylindrical enclosure of the cell 100 is folded radially inwards (see figure 11) such that the outer contact region 50 may be securely welded to the sidewall 110. The weld is indicated in figure 11, and may extend continuously around the circumference of the cylindrical secondary cell lid 1.

[0052] As is shown in all figures except 4 and 5, the cylindrical secondary cell lid 1 may comprise an annular support portion 60 arranged radially outside the off-center portions 31, 32, 33. In the present examples, the annular support portion 60 is axially separated Z2 (see especially figure 2) from the off-center portions 31, 32, 33. Typically, the annular support portion 60 may form a lowermost surface of the cell 100 when the cylindrical secondary cell lid 1 is attached, such that the annular support portion 60 may form a support surface on which the cell 100 may stand. The annular support portion 60 may increase the stability or structural rigidity of the cylindrical secondary cell lid 1. In addition, the annular support portion 60 may be beneficial for manufacture, as it may be gripped when the cylindrical secondary cell lid 1 is handled in assembly. For example, the annular support portion 60 may be gripped by a magnetic manipulator or by a vacuum manipulator. Preferably, as in the present examples, an axially outer surface, or axial end surface, of the annular support portion 60 is flat. A flat annular support portion 60 may provide a flat lowermost surface of the cell 100, in other words a stable support surface.

[0053] In the present examples, the roll contact regions 41, 42, 43, the off-center portions 31, 32, 33 and the support portion 60 are not coplanar. In some detail, the roll contact regions 41, 42, 43 are located axially closest to the axial sidewall 110 of the cell, or more precisely axially closest to the electrode roll 120 of the cell 100. The annular support portion 60 is located axially furthest from the axial sidewall 110 of the cell, or more precisely axially furthest from the electrode roll 120. The off-center portions 31, 32, 33 are located axially in-between the roll contact regions 41, 42, 43 and the support portion 60. The off-center portions 31, 32, 33 may be axially located roughly half ways between the roll contact regions 41, 42, 43 and the support portion 60.

[0054] Referring to figure 2, the off-center portions 31, 32, 33 and the center portion 20 may be located a first axial distance Z1 apart from the roll contact regions 41, 42, 43. The support portion 60 may be located a second axial distance Z2 apart from the off-center portions 31, 32, 33 and the center portion 20. The support portion 60 may be located a third axial distance Z3 from the roll contact regions 41, 42, 43.

[0055] Referring in particular to figures 2, 7, 11 and 13, the circumferential groove pattern section 11c, 12c, 13c of the off-center portions 31, 32, 33 may extend directly to the support portion 60. In some detail, the circumferential groove pattern section 11c, 12c, 13c of the off-center portions 31, 32, 33 may extend directly to a radially inner side of the support portion 60.

[0056] In the examples of figures 1 to 3 and 8 to 11, the support portion 60 is one single portion that continuously extends around the circumference of the cylindrical secondary cell lid 1. In the example of figures 6 and 7, and the example of figures 12 and 13, the support portion 60 instead comprises a plurality of support portion sections 61, 62, 63 that are circumferentially distanced from one another. As is illustrated, the plurality of support portion sections 61, 62, 63 may have an extension or length in the circumferential direction that exceeds the radial extension. The support portion sections 61, 62, 63 may be elongated, with a length (circumferential direction) that exceeds the width (radial direction).

[0057] The provision of a plurality of support portion sections 61, 62, 63 makes possible for the roll contact regions 41, 42, 43 to extend in-between the support portion sections 61, 62, 63. Thus, the roll contact regions 41, 42, 43 may have an extended radial extension, as compared to when the roll contact regions 41, 42, 43 are surrounded by a single support portion 60 (compare e.g. figures 1 and 6, and figures 2 and 7). Thus, the plurality of support portion sections 61, 62, 63 allows the roll contact regions 41, 42, 43 to provide a particularly large contact area for the electrode roll 120. In addition, welding the roll contact regions 41, 42, 43 to the electrode roll 120 may be facilitated as room for the welds is ensured.

[0058] The support portion sections 61, 62, 63 may be circumferentially separated. The circumferential spacing is preferably selected such that there is room for 2 to 6 radial weld lines to be applied side by side in each space. In the present example, the circumferential spacing approximately equals half to two times the width of the respective support portion section 61, 62, 63.

[0059] In the examples of figure 6 and 8, the cylindrical secondary cell lid 1 comprises one support portion section 61, 62, 63 for each one of the off-center portions 31, 32, 33. There are three support portion sections and three off-center portions. In other examples, there may be four support portion sections and four off-center portions (see figure 5). In the example of figures 6 and 7, and the example of figures 12 and 13, the respective circumferential groove pattern section 11c, 12c, 13c of the off-center portions 31, 32, 33 extends directly to a respective support portion section 61, 62, 63. In figures 7 and 13, it is clearly shown that the circumferential groove pattern section 12c of the second off-center portion 32a extends directly to a second support portion section 62.

[0060] As has been mentioned and is illustrated in figures 6 and 12, the cylindrical secondary cell lid 1 may be configured such that the roll contact regions 41, 42, 43 extend in-between the support portion sections 61, 62, 63.

[0061] In the present examples, the cylindrical secondary cell lid 1 comprises a first, or top, end surface and an opposing second, or bottom, end surface. The first end surface is in direct electrical contact with the electrode roll 120, more precisely the first end surface of the roll contact regions 41, 42, 43 is in direct electrical contact with the electrode roll 120. The cylindrical secondary cell lid 1 further comprises an outer circumferential surface. The outer circumferential surface is in direct electrical contact with the axial sidewall 110 of the cylindrical enclosure of the cell 100, more precisely the outer circumferential surface of the flange 55 (if present) is in direct electrical contact with the axial sidewall 110.

[0062] The groove pattern 10 of the present examples consist of a single groove or notch. The disclosure does however not exclude that the groove pattern is interrupted, such that it comprises more than one groove or notch along the groove pattern 10. The groove or notch may be referred to as a breakable portion and is in the present examples a thinning of the lid material that is configured to break before other parts of the cylindrical secondary cell lid 1 (and the cell enclosure). In the present example (see e.g. figures 2 and 14), the groove pattern 10 is a groove or notch made in both the first and the second end surfaces of the cylindrical secondary cell lid 1. Such a groove or notch may be beneficial for manufacturing efficiency. As is illustrated in figure 15, the groove or notch may be made only in the first or in the second end surface of the cylindrical secondary cell lid 1.

[0063] Referring to figures 2, 3 and 11, the present cell 100 that comprises the cylindrical secondary cell lid 1 may have the cylindrical secondary cell lid 1 arranged in direct electrical contact with the axial sidewall 110 of the cell enclosure and with the electrode roll 120. Thus, the cylindrical secondary cell lid 1 may be a single part that electrically connects the electrode roll 120 to the axial sidewall 110. In addition, the cylindrical secondary cell lid 1 may be a single part that mechanically connects the electrode roll 120 to the axial sidewall 110. Advantages may involve a reduction of parts and materials, easy manufacture and low internal resistance. The abovedescribed groove pattern 10 provides for safe venting. The relative size of the area of the vent opening formed by the groove pattern 10 in relation to the area of the roll contact regions 41, 42, 43 ensures secure and stable support for the electrode roll 120 and good electrical contact, together with safe venting. The present disclosure does not exclude that the roll contact regions 41, 42, 43 may detach from the electrode roll 120 and form an additional vent opening, at high overpressures. In the exemplified embodiments, the cell 100 is circular cylindrical. The cell 100 comprises a cylindrical enclosure having a first enclosure end, an opposite second enclosure end and an axial sidewall 110 or enclosure sidewall that extends between the enclosure ends.

[0064] In the present examples, the first and second enclosure ends are circular. The axial sidewall 110 is circular cylindrical. The cell 100, and thus its sidewall 110, may be elongated and extend along the longitudinal axis (Z-axis in figure 3). The enclosure ends may extend in planes (XY- planes in figure 3) that are perpendicular to the longitudinal axis.

[0065] The first enclosure end or terminal end (top end in figure 3) may be formed in one piece with the axial sidewall 110. There may be an undepicted electrical isolator arranged between the undepicted terminal part (e.g. a terminal rivet) and the first enclosure end. The second enclosure end or electrolyte filling end may be open, and the separate cylindrical secondary cell lid 1 may be attached to the axial sidewall 110 of the cell enclosure at the open enclosure end. Thus, the cylindrical secondary cell lid 1 may form the second enclosure end (bottom end in figure 3).

[0066] As is illustrated by the dashed circle in figure 3, The first enclosure end comprises a central terminal through-hole for the positive terminal. The negative terminal is electrically connected to the axial sidewall 110. More precisely, the negative terminal is formed by the top surface at the first enclosure end that surrounds the terminal through-hole. The entire cylindrical enclosure (apart from the positive terminal at the top end) and the cylindrical secondary cell lid are in the present examples at the electrical potential of the negative terminal.

[0067] As is illustrated in figures 2 and 3, the cell 100 may comprise an electrode roll 120. The electrode roll 20 comprises a first and a second conductive sheet, and typically separating means arranged there between. The separating means may also be termed separator. The conductive sheets and are rolled to form a circular cylindrical roll. The conductive sheets are coated with electrode coatings and on assembly of the cell 100, the cylindrical enclosure is filled with an electrolyte. The coatings on the conductive sheets act as cathode and anode, respectively. The cathode, anode and electrolyte provide electrochemical energy storage. This principle is known per se, and the electrode roll 120 is commonly referred to as a jellyroll.

[0068] The conductive sheets of the electrode roll 120 may be axially offset in relation to one another, and each conductive sheet may comprise an end section that is not coated with electrode coating. Via the non-coated end sections, the respective ends of the electrode roll 120 may be efficiently electrically connected to a respective assigned terminal of the cell 100. This design is known per se and commonly referred to as a tabless cell.

[0069] In the present example, a conductive sheet of the electrode roll 120 is in electrical contact, more precisely in direct electrical contact, with the cylindrical secondary cell lid 1. The conductive sheet in direct electrical contact with the cylindrical secondary cell lid 1 may be one of the rolled conductive sheets of the electrode roll 120. Typically, the cylindrical secondary cell lid 1 is welded, e.g. laser welded, to the conductive sheet. Thus, no additional separate component needs to be arranged to make contact with the conductive sheet. An edge of the rolled conductive sheet be folded to provide an electrical contact surface at the end of the electrode roll. Direct electrical contact may be referred to as physical contact.

[0070] The cylindrical secondary cell lid 1 may be formed from one single circular disc. Typically, the disc is a sheet metal blank. The cylindrical secondary cell lid 1 may be formed by deforming, e.g. stamping, a blank. Referring e.g. to figures 1 and 2, the off-center portions 31, 32, 33 may be referred to as protrusions or recesses made in the cylindrical secondary cell lid 1. Similarly, the at least one support portion 60 may be referred to as protrusions or recesses. The cylindrical secondary cell lid 1 of the present examples is one-piece.

[0071] As mentioned, the circumferential groove pattern sections 11c, 12c, 13c of the off-center portions 31, 32, 33 may extend directly to the support portion 60 (or support portion sections 61, 62, 63). Especially figures 2, 7, 11 and 13 shown that the axial protrusion or recess that forms the off-center portions 31, 32, 33 continues in the same axial plane to the axial protrusion or recess that forms support portion 60 (or support portion sections). In more detail, the radially outer end of each off-center portion 31, 32, 33 continues radially outwards in the same axial plane to the radially inner side of the axial protrusion or recess that forms the support portion 60. The radially outer side of the axial protrusion or recess that forms the support portion 60 originates from the plane of the roll contact regions 41, 42, 43.

[0072] In the example of figure 8 and 9, both the radially inner and the radially outer sides of the axial protrusion or recess that forms the support portion 60 originate from the plane of the roll contact regions 41, 42, 43. Thus, the circumferential groove pattern sections 11c, 12c, 13c of the off- center portions 31, 32, 33 do not extend directly to the annular support portion 60 (or support portion sections). In other words, the off-center portions (together with the center portion) and the support portion are formed as own separate protrusions or recesses. The cylindrical secondary cell lid 1 may be said to comprise or consist of a radially outer region, or outer region, an intermediate region, and a radially inner region, or inner region. The outer region may be annular and encircle the intermediate region, which may be annular. The intermediate region may in turn encircle the inner region.

[0073] The outer region may comprise the above-described outer contact region 50. The outer region may thus be configured to be attached to the axial sidewall 110, e.g. by welding. However, as is known to persons skilled in the art, there are other methods for attaching a lid to a cylindrical enclosure of an axial sidewall 110 of a cell 100. The intermediate region may comprise the above-described annular support portion 60 (or support portion sections 61, 62, 63). The inner region may comprise the above-described groove pattern 10.

[0074] At the center of the cylindrical secondary cell lid 1, there may as shown be a fill opening 5 providing for the above-described electrolyte filling. Thus, the fill opening 5 may be positioned within the center portion 20. The fill opening 5 may be sealed by a sealing element such as for example a rivet, such as a blind rivet. In figure 11, an exemplary sealing element 5e in the form of a seal plug is illustrated. For example, the sealing element or seal plug may be of a polymer material. In the present examples, the sealing element will not protrude axially beyond the cylindrical secondary cell lid 1. The reason being that annular support portion 60 is axially separated Z2 from the off-center portions 31, 32, 33. Figure 11 illustrates a seal cap 5c that covers the seal plug. The seal cap 5c may, as is illustrated, be welded to the cylindrical secondary cell lid 1. The seal plug may be relatively easy to fit in the fill opening 5 e.g. to stop contaminants from entering the cell 100, and a subsequent welding of the seal cap 5c over the seal plug and the fill opening 5 may ensure proper sealing.

[0075] Referring to figure 2, the electrode roll 20 may comprise a central electrolyte channel 125 or void (not shown). Figure 2 illustrates a certain radial gap between the axial sidewall 110 and the cylindrical secondary cell lid 1. It is to be apprehended that in actual realizations the cylindrical secondary cell lid 1 is in physical with the axial sidewall 110 and may be attached thereto for example by welding. Also, there is a certain axial gap illustrated between the electrode roll 120 and the roll contact regions 41, 42, 43. In an actual realizations, the roll contact regions 41, 42, 43 is in physical contact with the electrode roll 120 and may be attached thereto for example by welding. It is further pointed out that the electrode roll 120 is only schematically illustrated in figure 3. In actual realizations the electrode roll 120 is of greater axial extension or height, and typically comprises the electrolyte channel 125 shown in figure 2.

[0076] The exemplary groove patterns 10 disclosed in figures 1 to 13 may be of the profiles shown in figures 14 and 15. By profile, or groove profile, is here meant the shape of the groove when seen in cross-section. In other words, the shape that the groove or notch has when seen in-plane with the cylindrical secondary cell lid 1.

[0077] The groove profile of figure 14 comprises a groove or notch made in both the first and the second end surfaces of the cylindrical secondary cell lid 1. Thus, the groove profile of figure 14 is made from both the top and bottom side, i.e. is formed on both the inner surface and the outer surface of the lid 1.

[0078] The groove profile of figure 15 comprises a groove or notch made in only the first end surface of the cylindrical secondary cell lid 1. Thus, the groove profile of figure 15 is made only from the top side. Typically, the groove profile of figure 15 may comprise a groove or notch made only in the inner end surface (top surface in figure 15) of the cylindrical secondary cell lid 1, i.e. formed on the surface that faces the electrode roll 110 when the cylindrical secondary cell lid 1 is attached to the cylindrical enclosure of the cell 100.

[0079] The groove pattern 10 of figure 15 may be referred to as stepped. As is illustrated, the groove pattern 10 of figure 15 comprises a first groove and second grove that is made in the first groove. The first groove may be referred to as a shallow groove and the second groove may be referred to as deep grove. The first groove is wider than the second groove, as is illustrated, even though the width of the first groove may be exaggerated in figure 15.

[0080] As is illustrated, a relatively thin portion of the thickness of the cylindrical secondary cell lid 1 may remain where the second groove is formed. For example, the remaining thickness of the cylindrical secondary cell lid 1, where the groove pattern 10 of figure 15 is made, may be 10 to 30, or 10 to 20, percent of the original thickness of the cylindrical secondary cell lid 1. Such a groove pattern 10 may reliably break before other parts of the cylindrical secondary cell lid.

[0081] The groove pattern 10 of figure 15 may as mentioned be formed on an inner surface of the cylindrical secondary cell lid 1. Alternatively, the groove pattern 10 of figure 15 may be formed on an outer surface of the cylindrical secondary cell lid 1. The two-step groove pattern 10 may reliably break at the desired threshold value of the pressure to which the cylindrical secondary cell lid is subjected.

[0082] Modifications and other variants of the described embodiments will come to mind to ones skilled in the art having benefit of the teachings presented in the foregoing description and associated drawings. Therefore, it is to be understood that the embodiments are not limited to the specific example embodiments described in this disclosure and that modifications and other variants are intended to be included within the scope of this disclosure. For example, a cylindrical secondary cell lid, or a cylindrical secondary cell end, may be provided with the groove or notch described with reference to figure 15 without the lid or end comprising the other features of the lid described herein.

[0083] Furthermore, although specific terms may be employed herein, they are used in a generic and descriptive sense only and not for purposes of limitation. Therefore, persons skilled in the art would recognize numerous variations to the described embodiments that would still fall within the scope of the appended claims. As used herein, the terms “comprise / comprises” or “include / includes” do not exclude the presence of other elements or steps. Furthermore, although individual features may be included in different claims (or embodiments), these may possibly advantageously be combined, and the inclusion of different claims (or embodiments) does not imply that a certain combination of features is not feasible and / or advantageous. In addition, singular references do not exclude a plurality. Finally, reference numerals in the claims are provided merely as a clarifying example and should not be construed as limiting the scope of the claims in any way.

Claims

CLAIMS1. A cylindrical secondary cell lid (1) for a cylindrical secondary cell (100), the cylindrical secondary cell lid (1) comprising a groove pattern (10), which is configured to provide a vent opening in the cylindrical secondary cell lid (1) if a pressure to which the cylindrical secondary cell lid (1) is subjected reaches a threshold value, wherein the groove pattern (10) defines a center portion (20), a first off-center portion (31), a second off-center portion (32), and a third off-center portion (33), wherein the off-center portions (31, 32, 33) extend from the center portion (20) and are respectively formed by two radial groove pattern sections (11 a, 11b, 12a, 12b, 13a, 13b) and one circumferential groove pattern section (11c, 12c, 13c) that connects the two radial groove pattern sections (I la, 11b, 12a, 12b, 13a, 13b).

2. The cylindrical secondary cell lid (1) of claim 1, wherein the off-center portions (31, 32, 33) essentially have the shape of three petals, or wherein the cylindrical secondary cell lid (1) comprises a fourth off-center portion (34) and the off-center portions (31, 32, 33, 34) essentially have the shape of four petals.

3. The cylindrical secondary cell lid (1) of claim 1 or 2, comprising roll contact regions (41, 42, 43) arranged in-between the off-center portions (31, 32, 33).

4. The cylindrical secondary cell lid (1) claim 3, wherein the roll contact regions (41, 42, 43) are axially separated (Z 1 ) from the off-center portions (31, 32, 33) such that the roll contact regions (41, 42, 43) may be arranged in direct electrical contact with an electrode roll (120) arranged inside the cylindrical secondary cell (100), the off-center portions (31, 32, 33) being arranged at a distance from the electrode roll (110).

5. The cylindrical secondary cell lid (1) of claim 3 or 4, wherein the number of roll contact regions (41, 42, 43) is three.

6. The cylindrical secondary cell lid (1) according to any of claims 3 to 5, wherein the total area of the roll contact regions (41, 42, 43) corresponds 20 to 60 percent of the area of the cylindrical secondary cell lid (1).

7. The cylindrical secondary cell lid (1) of any preceding claim, comprising an outer contact region (50) that is adapted to be arranged in direct electrical contact with an axial sidewall (110) of a cylindrical enclosure of the cylindrical secondary cell (100).

8. The cylindrical secondary cell lid (1) of claim 7, wherein the outer contact region (50) comprises a flange (55) that is adapted to be arranged in direct electrical contact with the axial sidewall (110).

9. The cylindrical secondary cell lid (1) of any preceding claim, wherein the cylindrical secondary cell lid (1) is adapted to be arranged in direct electrical contact with an electrode roll (120) arranged inside the cylindrical secondary cell (100) and in direct electrical contact with an axial sidewall (110) of a cylindrical enclosure of the cylindrical secondary cell (100).

10. The cylindrical secondary cell lid (1) of any preceding claim, comprising an annular support portion (60) arranged radially outside the off-center portions (31, 32, 33) and axially separated (Z2) from the off-center portions (31, 32, 33).

11. The cylindrical secondary cell lid (1) of claim 10, wherein the circumferential groove pattern sections (11c, 12c, 13c) of the off-center portions (31, 32, 33) extend directly to the support portion (60).

12. The cylindrical secondary cell lid (1) according to claim 10 or 11, wherein the support portion (60) comprises a plurality of support portion sections (61, 62, 63) that are circumferentially distanced from one another.

13. The cylindrical secondary cell lid (1) according to any of claims 10 to 12, wherein the annular support portion (60), or support portion sections (61, 62, 63), comprises a flat axial end surface, which flat axial end surface may facilitate gripping the cylindrical secondary cell lid (1) and may provide a stable support surface.

14. The cylindrical secondary cell lid (1) of claim 12 or 13, comprising one support portion section (61, 62, 63) for each one of the off-center portions (31, 32, 33), wherein each one of the groove pattern sections (11c, 12c, 13c) of the off-center portions (31, 32, 33) extend directly to the support portion sections (61, 62, 63).

15. The cylindrical secondary cell lid (1) of claims 4 and 12, 13 or 14, configured such that roll contact regions (41, 42, 43) extend in-between the support portion sections (61, 62, 63).

16. The cylindrical secondary cell lid (1) of any preceding claim, wherein the grove pattern (10) is stepped, wherein the groove pattern (10) comprises a first groove and a second groove, the second groove being formed at the bottom of the first groove.

17. The cylindrical secondary cell lid (1) of claim 16, wherein the groove pattern (10) is formed on an inner surface, and not on an outer surface, of the cylindrical secondary cell lid (1).

18. A cylindrical secondary cell (100) comprising the cylindrical secondary cell lid (1) of any preceding claim.

19. The cylindrical secondary cell (100) of claim 18, comprising a cylindrical enclosure with an axial sidewall (110) and an electrode roll (120) arranged inside the cylindrical enclosure, wherein the cylindrical secondary cell lid (1) is arranged in direct electrical contact with the axial sidewall (110) and with the electrode roll (120).

20. The cylindrical secondary cell (100) of claim 19, wherein the cylindrical secondary cell lid (1) comprises roll contact regions (41, 42, 43) arranged in-between the off-center portions (31, 32, 33), and wherein the roll contact regions (41, 42, 43) are arranged in direct electrical contact with the electrode roll (120).

21. A battery system comprising the cylindrical secondary cell (100) according to any of claims 18 to 20.

22. A vehicle system comprising the cylindrical secondary cell (100) according to any of claims 18 to 20.

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