Secondary batteries

Abstract

To provide a secondary battery which is compatible with both methods of laser welding and ultrasonic bonding, as a method for joining a lid member and a cap.SOLUTION: One aspect of the present disclosure provides a secondary battery including a lid member 12 and a cap 31. The lid member 12 includes a protrusion 24 formed around a liquid injection port 21, on a top face 22 of the lid member 12 on a side where the cap 31 is laser welded or ultrasonically bonded in a plate thickness direction. The cap 31 includes: a groove 42 that is formed on a first surface 41 of one surface of the cap 31 in the plate thickness direction and that can be engaged with the protrusion 24; and a smooth surface 44 that is formed on a second surface 43 of the other surface of the cap 31 in the plate thickness direction and that can be brought into surface contact with the tip surface of the protrusion 24. The outer peripheral surface formed on the outer periphery of the cap 31 is inclined toward the inside of the cap 31 along the way from a first surface 41 side to a second surface 43 side.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to secondary batteries. [Background technology]

[0002] As a conventional technology related to secondary batteries, Patent Document 1 discloses a secondary battery in which a cap is joined to a lid member by ultrasonic bonding so as to cover a protrusion (rib) formed around the liquid inlet in the lid member, and the liquid inlet is sealed by the cap. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-68648 Summary of the Invention [Problem to be solved by the invention]

[0004] In the secondary battery disclosed in Patent Document 1, the lid member and the cap are ultrasonically joined, but if the lid member and the cap are laser welded, the welding is thought to occur at the position of the protrusion. In this case, electrolyte may adhere to the protrusion formed around the injection hole, which may result in poor welding at the weld. Thus, the secondary battery disclosed in Patent Document 1 may be compatible with ultrasonic joining as a method for joining the lid member and the cap, but may not be compatible with laser welding.

[0005] Therefore, the present disclosure has been made to solve the above-mentioned problems, and aims to provide a secondary battery that can be used with both laser welding and ultrasonic bonding methods to join the lid member and the cap. [Means for solving the problem]

[0006] One aspect of the present disclosure made to solve the above-described problems provides a secondary battery having a case having an opening, a plate-shaped lid member sealing the opening, a liquid filler hole formed in the lid member so as to penetrate the lid member in a plate thickness direction and for pouring an electrolyte into the case, and a plate-shaped cap laser-welded or ultrasonically bonded to the lid member to seal the liquid filler hole, the lid member having a protrusion formed around the liquid filler hole on a surface of the lid member in the plate thickness direction on which the cap is laser-welded or ultrasonically bonded, the cap having a groove formed on a first surface that is one surface of the cap in the plate thickness direction and capable of fitting with the protrusion, and a smooth surface formed on a second surface that is the other surface of the cap in the plate thickness direction and capable of surface-to-surface contact with a tip surface of the protrusion, and an outer peripheral surface formed on an outer periphery of the cap is inclined toward the inside of the cap as it moves from the first surface side to the second surface side the smooth surface is brought into surface contact with the tip surface of the protrusion when the lid member and the cap are ultrasonically joined together; It is characterized by:

[0007] According to this aspect, the lid member and the cap can be laser welded together after the protrusion of the lid member is fitted into the groove of the cap. Furthermore, the lid member and the cap can be ultrasonically bonded together after the tip surface of the protrusion of the lid member is brought into surface contact with the smooth surface of the cap. In this way, the cap can be reversibly bonded to the lid member, and both laser welding and ultrasonic bonding can be used as methods for bonding the lid member and the cap.

[0008] Furthermore, the outer peripheral surface of the cap is inclined inward from the first surface side toward the second surface side. This makes it possible to form a wedge-shaped gap between the inclined outer peripheral surface of the cap and the lid member. Therefore, by performing laser welding at the outer peripheral surface of the cap during laser welding, the absorption rate of the laser light is improved due to the Fresnel absorption effect, making it possible to reduce the laser welding output and reduce leak defects due to voids in the welded portion.

[0009] In the above aspect, it is preferable that the first surface of the cap faces the lid member, the protrusion and the groove are engaged, and then the lid member and the cap are laser welded at the outer peripheral surface of the cap.

[0010] According to this aspect, the positioning accuracy of the cap is improved by fitting the protrusion and the groove. The protrusion also prevents the electrolyte from penetrating into the welded portion. Furthermore, since laser welding is performed at a position on the outer circumferential surface of the cap, which is not a protrusion, poor welding due to the electrolyte adhering to the welded portion can be reduced.

[0013] In the above aspect, it is preferable that the cap has a safety valve function portion that releases the internal pressure of the secondary battery when the internal pressure of the secondary battery reaches or exceeds a predetermined pressure.

[0014] According to this aspect, the cap has a safety valve function, so that the internal pressure of the secondary battery can be prevented from becoming excessive. Another aspect of the present disclosure made to solve the above problems is a secondary battery having a case having an opening, a plate-shaped lid member sealing the opening, a liquid fill port formed in the lid member so as to penetrate the lid member in a plate thickness direction and for pouring an electrolyte into the case, and a plate-shaped cap laser-welded or ultrasonically bonded to the lid member to seal the liquid fill port, wherein the lid member has a protrusion formed around the liquid fill port on a surface of the lid member on the side to which the cap is laser-welded or ultrasonically bonded in the plate thickness direction, and the cap The cap has a groove formed on a first surface, which is one surface in the thickness direction of the cap, that can fit into the protrusion, and a smooth surface formed on a second surface, which is the other surface in the thickness direction of the cap, that can come into surface contact with the tip surface of the protrusion, and the outer peripheral surface formed on the outer periphery of the cap slopes toward the inside of the cap as it moves from the first surface side to the second surface side, and the second surface of the cap faces the lid member, bringing the tip surface of the protrusion and the smooth surface into surface contact, and then the lid member and the cap are ultrasonically bonded together. According to this aspect, the tip surfaces of the protrusions of the lid member slide against the smooth surface of the cap, causing the protrusions to deform as they heat up, forming a bonded portion with a sealing function. Furthermore, during ultrasonic bonding, the repulsive force caused by the squeeze effect removes any electrolyte adhering to the protrusions, resulting in a clean contact surface between the lid member and the cap. Therefore, the portion where the lid member and the cap are ultrasonically bonded can be less susceptible to the effects of electrolyte adhering. In the above aspect, it is preferable that the cap has a safety valve function portion that releases the internal pressure of the secondary battery when the internal pressure of the secondary battery reaches or exceeds a predetermined pressure. According to this aspect, the cap has a safety valve function, so that the internal pressure of the secondary battery can be prevented from becoming excessive. [Effects of the Invention]

[0015] The secondary battery of the present disclosure can be used to join the lid member and the cap using both laser welding and ultrasonic bonding. [Brief explanation of the drawings]

[0016] [Figure 1] 1 is an overall perspective view of a secondary battery according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view taken along the line AA in FIG. 1. [Figure 3] FIG. 2 is a top view of the liquid injection port in the lid member and its surrounding area. [Figure 4] FIG. [Figure 5]5 is a cross-sectional view of the cap (cross-sectional view taken along line BB in FIG. 4). [Figure 6] 10A and 10B are views showing a case where the lid member and the cap are laser-welded together. [Figure 7] FIG. 2 is an enlarged view of a portion to be laser welded. [Figure 8] 10A and 10B are views showing a case where the lid member and the cap are ultrasonically joined together. [Figure 9] FIG. 2 is an enlarged view of the ultrasonic bonding portion. [Figure 10] 10 is a diagram showing that the electrolyte is separated from the protrusion due to repulsive force during ultrasonic bonding. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0017] Hereinafter, an embodiment of the secondary battery of the present disclosure will be described.

[0018] 1, the secondary battery 1 of this embodiment has a case 11 with an opening 11a and a rectangular plate-shaped lid member 12 that seals the opening 11a. The case 11 and the lid member 12 are made of metal (e.g., aluminum). The secondary battery 1 also has an electrode terminal 13 on the lid member 12.

[0019] 2 and 3, the lid member 12 has a liquid filling port 21 formed to penetrate the lid member 12 in the thickness direction (the vertical direction in FIG. 2). The liquid filling port 21 is a through hole for pouring an electrolyte into the case 11.

[0020] 1 and 2, the secondary battery 1 has a disk-shaped cap 31 that seals the liquid inlet 21. In this embodiment, the cap 31 is joined to the lid member 12 by laser welding or ultrasonic welding to seal the liquid inlet 21. Note that FIG. 2 shows an example in which the cap 31 is laser welded to the lid member 12.

[0021] In this embodiment, as shown in Fig. 2, the lid member 12 has a protrusion 24 formed in a recess 23 on its upper surface 22 (i.e., the surface of the lid member 12 in the thickness direction on which the cap 31 is laser welded or ultrasonically bonded) so as to protrude upward from the recess 23. As shown in Fig. 3, this protrusion 24 is formed in a circular bank shape all around the periphery of the pouring port 21.

[0022] 2 and 5, the cap 31 has a groove 42 formed in a first surface 41, which is one surface in the thickness direction of the cap 31 (the lower surface in FIGS. 2 and 5), so as to be recessed toward a second surface 43 of the cap 31. As shown in FIG. 2, the groove 42 can be fitted with the protrusion 24 of the lid member 12. The groove 42 is formed, for example, by press working.

[0023] 2, 4, and 5, the cap 31 has a smooth surface 44 formed flat in the radial direction (the left-right direction in FIGS. 2 and 5) of the cap 31 on a second surface 43, which is the other surface in the plate thickness direction of the cap 31 (the upper surface in FIGS. 2 and 5). This smooth surface 44 is capable of surface contact with the tip surface 51 of the protrusion 24, as shown in FIGS. 8 to 10, which will be described later.

[0024] Furthermore, as shown in FIG. 5, an outer peripheral surface 45 (the surface in the left-right direction in FIG. 5) formed on the outer periphery of the cap 31 is inclined toward the inside of the cap 31 as it moves from the first surface 41 side toward the second surface 43 side.

[0025] In this embodiment, the lid member 12 and the cap 31 can be laser welded and ultrasonically bonded together.

[0026] First, a case where the lid member 12 and the cap 31 are laser-welded will be described. In this case, as shown in FIG. 6, the first surface 41 of the cap 31 is faced toward the lid member 12, and the cap 31 is brought close to the lid member 12. Then, as shown in FIG. 7, the protrusion 24 of the lid member 12 is fitted into the groove 42 of the cap 31. Then, the wall 25 of the lid member 12 (i.e., the portion that rises upward from the recess 23) and the outer peripheral surface 45 of the cap 31 are laser-welded not at the position of the protrusion 24 but at the position of the outer peripheral surface 45 of the cap 31. In this way, in this embodiment, the lid member 12 and the cap 31 can be laser-welded.

[0027] Next, a case where the lid member 12 and the cap 31 are ultrasonically bonded together will be described. In this case, as shown in Figures 8 and 9, the second surface 43 of the cap 31 faces the lid member 12, and the tip surface 51 of the protrusion 24 of the lid member 12 and the smooth surface 44 of the cap 31 are brought into surface contact. Then, as shown in Figure 10, the lid member 12 and the cap 31 are ultrasonically bonded together. In this way, in this embodiment, the lid member 12 and the cap 31 can be ultrasonically bonded together.

[0028] As described above, in the secondary battery 1 of this embodiment, the lid member 12 has the protrusion 24 formed on the upper surface 22 around the filling hole 21. The cap 31 has the groove 42 on its first surface 41 that can fit with the protrusion 24. The cap 31 also has the smooth surface 44 on its second surface 43 that can come into surface contact with the tip surface 51 of the protrusion 24.

[0029] As a result, the protrusion 24 of the lid member 12 can be fitted into the groove 42 of the cap 31, and then the lid member 12 and the cap 31 can be laser welded together. Also, the tip surface 51 of the protrusion 24 of the lid member 12 can be brought into surface contact with the smooth surface 44 of the cap 31, and then the lid member 12 and the cap 31 can be ultrasonically bonded together. In this way, the cap 31 can be reversibly bonded to the lid member 12, and both laser welding and ultrasonic bonding can be used as methods for bonding the lid member 12 and the cap 31.

[0030] When laser welding the lid member 12 and the cap 31, the first surface 41 of the cap 31 is faced toward the lid member 12, the protrusion 24 is engaged with the groove 42, and then the lid member 12 and the cap 31 are laser welded at the position of the outer peripheral surface 45 of the cap 31.

[0031] In this way, by fitting protrusion 24 into groove 42, the positioning accuracy of cap 31 is improved. That is, the centering accuracy of cap 31 (the accuracy of aligning the center of pouring hole 21 with the center of cap 31), which is important during laser welding, is improved. Furthermore, protrusion 24 can prevent electrolyte from penetrating into the welded portion. Furthermore, because laser welding is performed at a position on outer peripheral surface 45 of cap 31, which is not a position where protrusion 24 is present, poor welding due to electrolyte adhering to the welded portion can be reduced.

[0032] 7, the lid member 12 and the cap 31 are in contact (line contact in FIG. 7) between the tip surface 51 of the protrusion 24 of the lid member 12 and the bottom surface 61 of the groove 42 of the cap 31, while the side surface 52 of the protrusion 24 of the lid member 12 and the side surface 62 of the groove 42 of the cap 31 are not in contact. In this way, the contact area between the protrusion 24 and the groove 42 is reduced, which reduces heat conduction between the protrusion 24 and the groove 42 during laser welding, thereby suppressing a temperature rise in the cap 31. Furthermore, this also reduces leakage defects caused by voids in the welded portion due to an increase in the internal pressure of the secondary battery 1 during laser welding.

[0033] Furthermore, outer peripheral surface 45 of cap 31 is inclined inward of cap 31 from first surface 41 toward second surface 43. Therefore, as shown in Fig. 7, it is possible to form a wedge-shaped gap between inclined outer peripheral surface 45 of cap 31 and wall portion 25 of lid member 12. Therefore, during laser welding, the absorption rate of laser light is improved due to Fresnel absorption, making it possible to reduce the laser welding output and reducing leak defects due to the generation of voids in the weld.

[0034] Furthermore, when ultrasonically joining the lid member 12 and the cap 31, the second surface 43 of the cap 31 is faced toward the lid member 12, and the tip surface 51 of the protrusion 24 and the smooth surface 44 of the cap 31 are brought into surface contact, and then the lid member 12 and the cap 31 are ultrasonically joined.

[0035] As a result, the tip surface 51 of the protrusion 24 of the lid member 12 slides against the smooth surface 44 of the cap 31, causing the protrusion 24 to deform as the temperature rises, forming a joint with a sealing function.

[0036] 10, during ultrasonic bonding, ultrasonic vibrations (vibrations shown by waveforms in FIG. 10) are applied to cap 31, which generates a squeeze effect that causes a repulsive force that expels the electrolyte from protrusion 24, resulting in a clean contact surface between tip end surface 51 of protrusion 24 and smooth surface 44 of cap 31. This makes it possible to reduce the influence of adhesion of electrolyte at the portion where lid member 12 and cap 31 are ultrasonically bonded.

[0037] 4 and 5, the cap 31 is provided with a safety valve function part 46 that releases the internal pressure of the secondary battery 1 when the internal pressure of the secondary battery 1 reaches or exceeds a predetermined pressure. The safety valve function part 46 is formed at a position inside the outer periphery of the cap 31 (i.e., the part where the groove part 42 and the smooth surface 44 are formed), and its thickness is formed to be smaller than the thickness of the outer periphery of the cap 31.

[0038] In this way, the cap 31 is provided with a safety valve function, thereby preventing the internal pressure of the secondary battery 1 from becoming excessive. Furthermore, in this embodiment, the variation in the opening pressure of the safety valve function portion 46 can be reduced by reducing residual strain due to heat input. That is, in the prior art, the safety valve is incorporated into the lid member, and after the lid member is welded to the case, the lid member tends to shrink, generating tensile residual stress in the safety valve and resulting in variation in the opening pressure of the safety valve. In contrast, in this embodiment, after the lid member 12 is welded to the case 11 and electrolyte is poured into the case 11 through the filling port 21, the cap 31 equipped with the safety valve function portion 46 is joined to the lid member 12. Therefore, the tensile residual stress that occurs in the safety valve function portion 46 in the prior art is unlikely to occur, thereby reducing variation in the opening pressure of the safety valve function portion 46.

[0039] It should be noted that the above-described embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible within the scope of the gist of the present disclosure.

[0040] In the above description, the terms "top" and "upper" are used for convenience and do not restrictively define the vertical orientation of the secondary battery 1. In other words, the vertical orientation of the secondary battery 1 can change. [Explanation of symbols]

[0041] 1 Secondary battery 11 cases 11a opening 12 Lid member 13 Electrode terminal 21 Filling port 22 Top side 23 Recess 24 Protrusion 25 Wall 31 Cap 41 Page 1 42 Groove 43 2nd page 44 Smooth surface 45 Outer surface 46 Safety valve function part 51 Tip surface 52 Side 61 bottom 62 Side

Claims

1. a case having an opening; a plate-shaped lid member that seals the opening; a liquid injection port formed in the lid member so as to penetrate the lid member in a plate thickness direction, for injecting an electrolyte into the case; a plate-shaped cap that is laser-welded or ultrasonically bonded to the lid member to seal the liquid inlet; In a secondary battery having the lid member includes a protrusion formed around the pouring port on a surface of the lid member in a thickness direction on which the cap is laser welded or ultrasonically joined, The cap is a groove formed on a first surface of the cap, the first surface being one surface in a thickness direction of the cap, the groove being capable of being fitted with the protrusion; a smooth surface formed on a second surface, which is the other surface in the plate thickness direction of the cap, and capable of surface contact with the tip surface of the protrusion, an outer peripheral surface formed on the outer periphery of the cap is inclined toward the inside of the cap as it moves from the first surface side to the second surface side, the smooth surface is in surface contact with the tip surface of the protrusion when the lid member and the cap are ultrasonically joined; A secondary battery characterized by:

2. 2. The secondary battery of claim 1, The first surface of the cap faces the lid member, and the protrusion and the groove are fitted together. the lid member and the cap are laser-welded at the outer peripheral surface of the cap; A secondary battery characterized by:

3. 3. The secondary battery of claim 1, the cap has a safety valve function portion that releases the internal pressure of the secondary battery when the internal pressure of the secondary battery reaches or exceeds a predetermined pressure; A secondary battery characterized by:

4. A case having an opening; a plate-shaped lid member that seals the opening; a liquid injection port formed in the lid member so as to penetrate the lid member in a plate thickness direction, for injecting an electrolyte into the case; a plate-shaped cap that is laser-welded or ultrasonically bonded to the lid member to seal the liquid inlet; In a secondary battery having the lid member includes a protrusion formed around the pouring port on a surface of the lid member in a thickness direction on which the cap is laser welded or ultrasonically joined, The cap is a groove formed on a first surface of the cap, the first surface being one surface in a thickness direction of the cap, the groove being capable of being fitted with the protrusion; a smooth surface formed on a second surface, which is the other surface in the plate thickness direction of the cap, and capable of surface contact with the tip surface of the protrusion, an outer peripheral surface formed on the outer periphery of the cap is inclined toward the inside of the cap as it moves from the first surface side to the second surface side, The second surface of the cap is directed toward the lid member, and the tip surface of the protrusion is brought into surface contact with the smooth surface. the lid member and the cap are ultrasonically bonded together; A secondary battery characterized by:

5. The secondary battery of claim 4, the cap has a safety valve function portion that releases the internal pressure of the secondary battery when the internal pressure of the secondary battery reaches or exceeds a predetermined pressure; A secondary battery characterized by:

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