Patent Application
20250233260
This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2024-003420 filed on Jan. 12, 2024, the entire contents of which are incorporated herein by reference.
The disclosure relates to a power storage device in which a safety valve portion of a pressure relief type is provided in a case member that is made of metal and constitutes a case.
As a power storage device, a battery is known in which a safety valve portion of a pressure relief type is provided in a case made of metal. The safety valve portion fractures and opens when the internal pressure of the case exceeds the valve opening pressure, to release gas in the case to the outside of the case. The safety valve portion is formed by reducing the thickness of a part of a case member (e.g., a case lid member) by press working or partially forming a groove for fracturing and opening by press working. One example of the battery equipped with the safety valve portion is described in Japanese unexamined patent application publication No. 2018-032605 (JP 2018-032605 A).
However, when the safety valve portion is formed integrally with the case member by pressing a part of the case member as described above, it may be difficult to properly form the safety valve portion in a desired shape, depending on the thickness and material of the case member. For example, if the thickness of the case member is increased as the size of the battery increases, it may be difficult to form the safety valve portion having a thickness that provides a desired valve opening pressure and a suitable thickness at the bottom of the groove as an integral part of the case member.
The disclosure was made in view of the situation as described above, and provides a power storage device in which a safety valve portion of a pressure relief type can be easily provided in a case member, regardless of the thickness and material of the case member made of metal.
In the power storage device described above, the safety valve member including the pressure relief type safety valve portion that fractures and opens when the internal pressure of the case rises is fixed to the case member via the valve fixing resin member encircling the safety valve member or extending endlessly around the safety valve member. The safety valve member is a separate member from the case member and is formed separately from the case member; therefore, the safety valve member of a desired shape can be properly formed without being affected by the thickness and material of the case member. Then, the safety valve member is fixed to the case member via the valve fixing resin member, so that the safety valve portion can be easily provided in the case member.
The valve fixing resin member made of resin is softer than the case member made of metal. Therefore, even if distortion occurs in the case member when the case is formed using the case member, distortion is less likely or unlikely to occur in the safety valve member connected to the case member via the valve fixing resin member. Thus, in the power storage device described above, even if distortion occurs in the case member, there is little distortion in the safety valve member, and the adverse influence on the valve opening pressure of the safety valve portion, for example, can be reduced.
Examples of the “power storage device” include secondary batteries, such as a lithium-ion secondary battery, sodium-ion secondary battery, and a calcium-ion secondary battery, and capacitors, such as a lithium-ion capacitor.
The safety valve member and the valve fixing resin member constitute the thermal relief type safety valve that opens with a rise in temperature. That is, the above power storage device has the thermal relief type safety valve as well as the pressure relief type safety valve portion. This can make the power storage device even safer.
portion of the case member may include a hole surrounding roughened portion that extends endlessly over the entire circumference of the hole surrounding portion and has nanocolumns formed by joining particles derived from the metal that forms the case member together like strings of beads into the form of columns and having a height of 50 nm or more, the nanocolumns standing numerously on the hole surrounding roughened portion, and the valve fixing resin member may be hermetically joined to the hole surrounding roughened portion over the entire circumference such that the resin material that forms the valve fixing resin member fills gaps between the nanocolumns standing numerously.
In the power storage device described above, the hole surrounding portion of the case member is provided with the nano-level (nano-order) hole surrounding roughened portion on which the nanocolumns described above stand numerously, and the valve fixing resin member is hermetically joined to the hole surrounding roughened portion with the resin material filling gaps between the nanocolumns standing numerously. Therefore, the seal performance and joining strength between the hole surrounding portion of the case member and the valve fixing resin member can be enhanced.
In the power storage device described above, the peripheral portion of the safety valve member is provided with the nano-level valve periphery roughened portion on which the nanocolumns stand numerously, and the valve fixing resin member is hermetically joined to the valve periphery roughened portion with the resin material filling gaps between the nanocolumns standing numerously. Therefore, the seal performance and joining strength between the peripheral portion of the safety valve member and the valve fixing resin member can be enhanced.
Since the safety valve member is formed using a thin aluminum plate with the thickness of 500 μm or less, the safety valve portion can be easily and highly accurately formed by press forming. Thus, the power storage device is equipped with the safety valve member in which the valve opening pressure of the safety valve portion is particularly stable.
When the safety valve portion is formed as an integral part of the case member by pressing a part of the case member as in the known power storage device, it may be difficult to press-form the safety valve portion integrally with the case member if the thickness of the case member made of aluminum is equal to or greater than 600 μm. In contrast, in the power storage device described above, the case member and the safety valve member are separate members; therefore, the safety valve portion can be easily and highly accurately press-formed in the safety valve member, regardless of the thickness of the case member. Accordingly, even if the case member is formed from an aluminum plate with the thickness of 600 μm or more, the power storage device is equipped with the safety valve member in which the valve opening pressure of the safety valve portion is particularly stable.
In some cases, it is desirable to use a case member made of a metal, such as stainless steel, other than aluminum as the case member. In the power storage device described above, since the case member and the safety valve member are separate members, the safety valve portion can be easily and highly accurately press-formed in the safety valve member, regardless of the material of the case member. Accordingly, the power storage device described above is equipped with the safety valve member in which the valve opening pressure of the safety valve portion is particularly stable, even though the case member is made of a metal other than aluminum.
In the following, one embodiment of the disclosure will be described with reference to the drawings.
The battery 1 is a sealed lithium-ion secondary battery of a rectangular (rectangular parallelepiped) shape, which is installed on a vehicle, such as a hybrid vehicle, plug-in hybrid vehicle, or an electric vehicle. The battery 1 consists of a case 10 made of metal and provided with the safety valve portion 31, an electrode body 50 and electrolyte 5 housed in the case 10, positive and negative terminal members 60 fixed to the case 10 via respective terminal fixing resin members 70, and so forth. The electrode body 50 is covered with an insulating holder 7 in the case 10. The insulating holder 7 is formed from an insulating film and shaped like a bag that opens to the upper side AH1 in the battery height direction AH.
The electrode body 50 is of a rectangular parallelepiped, stacked type, and has a plurality of rectangular positive electrode sheets 51 and a plurality of rectangular negative electrode sheets 52 alternately stacked in the battery thickness direction CH via rectangular separators 53 each made from a porous resin film. In the electrode body 50, on one side BH1 in the battery width direction BH, current collecting foils of the respective positive electrode sheets 51 are superposed in the battery thickness direction CH to form a positive current collector 50c. Also in the electrode body 50, on the other side BH2 in the battery width direction BH, current collecting foils of the respective negative electrode sheets 52 are superposed in the battery thickness direction CH to form a negative current collector 50d.
The case 10 is shaped like a rectangular parallelepiped box and made of metal (aluminum in this embodiment). The case 10 consists of a case body 11 that is in the form of a rectangular tube with a bottom and a rectangular opening portion 11c and houses the electrode body 50 therein, and a case lid member 21 in the form of a rectangular plate that closes the opening portion 11c of the case body 11. The opening portion 11c of the case body 11 and a peripheral portion 21f of the case lid member 21 are hermetically welded together over the entire circumference thereof. In this embodiment, the case lid member 21 corresponds to the “case member” mentioned above. The case lid member 21 is formed from an aluminum plate having a thickness ta (see
In the case lid member 21, an elliptic valve hole 21i is provided around the center as viewed in the battery width direction BH. A safety valve member 30 in the form of an elliptic plate including a safety valve portion 31 of a pressure relief type is mounted in the valve hole 21i via an elongated annular valve fixing resin member 40 (see
The safety valve member 30 is a metal plate (an aluminum plate in this embodiment) in the shape of an ellipse that is slightly smaller than the valve hole 21i and has a thickness tb of 500 μm or less (the thickness tb is equal to 80 μm in this embodiment) that is smaller than the thickness ta of the case lid member 21. The dimension of the safety valve member 30 measured in the long-side (major-axis) direction (the battery width direction BH) is 15 mm, and the dimension measured in the short-side (minor-axis) direction (the battery thickness direction CH) is 5 mm. In this embodiment, the whole of the central portion of the safety valve member 30 excluding the peripheral portion 33 provides the pressure relief type safety valve portion 31 that fractures and opens when the internal pressure of the case 10 exceeds the valve opening pressure. The safety valve portion 31 is press-formed, and has a fracture section 32 of a predetermined shape consisting of V-shaped grooves. The thickness measured at the bottom of the V-shaped grooves of the fracture section 32 (i.e., the thickness of the thinnest part of the safety valve portion 31) is 50 μm.
The valve fixing resin member 40 is joined to the peripheral portion 33 of the safety valve member 30. Specifically, regions of the surface 33m of the peripheral portion 33 excluding an outer peripheral end surface, i.e., a peripheral portion outer surface 33ma facing the outside (the upper side AH1 in this embodiment) and a peripheral portion inner surface 33mb facing the inside (the lower side AH2 in the battery height direction AH in this embodiment), each have an elongated annular shape extending over the entire circumference of the peripheral portion 33, and provide valve periphery roughened portions 34 (a first valve periphery roughened portion 34a and a second valve periphery roughened portion 34b) that are roughened. The width (sealing width) of each of the first valve periphery roughened portion 34a (the peripheral portion outer surface 33ma) and the second valve periphery roughened portion 34b (the peripheral portion inner surface 33mb) is 0.5 mm or more (0.5 mm in this embodiment).
The valve periphery roughened portion 34 is a nano-level nano-roughened portion that is roughened with a pulsed laser beam LB that will be described below (see
The valve fixing resin member 40 is also joined to the hole surrounding portion 23 of the case lid member 21. Specifically, regions of the surface 23m of the hole surrounding portion 23 excluding a hole inner circumferential surface, i.e., a surrounding portion outer surface 23ma facing the outside (the upper side AH1 in this embodiment) and a surrounding portion inner surface 23mb facing the inside (the lower side AH2 in this embodiment), each have an elongated annular shape extending over the entire circumference of the hole surrounding portion 23, and provide hole surrounding roughened portions 24 (a first hole surrounding roughened portion 24a and a second hole surrounding roughened portion 24b) that are roughened. The width (sealing width) of each of the first hole surrounding roughened portion 24a (the surrounding portion outer surface 23ma) and the second hole surrounding roughened portion 24b (the surrounding portion inner surface 23mb) is 0.5 mm or more (0.5 mm in this embodiment).
Like the valve periphery roughened portion 34 of the safety valve member 30 described above, the hole surrounding roughened portion 24 is a nano-level nano-roughened portion. Specifically, the hole surrounding roughened portion 24 has numerous bowl-shaped recesses 25 (see
The valve fixing resin member 40 is made of a thermoplastic resin material 41. The resin material 41 includes a thermoplastic main resin (polyphenylene sulfide (PPS) in this embodiment), a thermoplastic elastomer (thermoplastic polyurethane elastomer in this embodiment), and a filler (fibrous glass filler in this embodiment). With the resin material 41 filling gaps between the nanocolumns 36 standing numerously on the valve periphery roughened portions 34 of the safety valve member 30, the valve fixing resin member 40 is hermetically joined with strong joining force to the valve periphery roughened portions 34 over the entire circumference. With the resin material 41 filling gaps between the nanocolumns 26 standing numerously on the hole surrounding roughened portions 24 of the case lid member 21, the valve fixing resin member 40 is also hermetically joined with strong joining force to the hole surrounding roughened portions 24 over the entire circumference.
The above resin material 41 that forms the valve fixing resin member 40 softens or melts at approximately 250° C. Therefore, the valve fixing resin member 40 and the safety valve member 30 described above constitute a thermal relief type safety valve 45 that opens as the resin material 41 softens or melts when the temperature of the valve fixing resin member 40 rises, more specifically, when the temperature of the valve fixing resin member 40 reaches about 250° C.
Next, the terminal members 60 and the terminal fixing resin members 70 will be described (see
Each terminal member 60 is formed by pressing a metal plate (an aluminum plate for the positive electrode, a copper plate for the negative electrode). The terminal member 60 consists of a terminal top plate 60a in the form of a rectangular plate located on the upper side AH1 of the case lid member 21 and extending in the battery width direction BH and the battery thickness direction CH, and a terminal extension 60b extending from the terminal top plate 60a to the lower side AH2 in the battery height direction AH. The terminal extension 60b is bent at an end portion of the terminal top plate 60a on one side CH1 in the battery thickness direction CH and extends to the lower side AH2 through the insertion hole 21h of the case lid member 21, and further through the terminal fixing resin member 70. The terminal extension 60b of the positive electrode is welded at its distal end portion on the lower side AH2 to the positive current collector 50c of the electrode body 50. On the other hand, the terminal extension 60b of the negative electrode is welded at its distal end portion on the lower side AH2 to the negative current collector 50d of the electrode body 50.
The terminal fixing resin member 70 is made of a thermoplastic resin material 71. The resin material 71 is the same as the resin material 41 that forms the valve fixing resin member 40 in this embodiment, but the resin material 71 and the resin material 41 may be different resin materials. The terminal fixing resin member 70 is hermetically joined to a portion of the case lid member 21 surrounding the insertion hole 21h, and also hermetically joined to a portion of the terminal member 60 near the insertion hole 21h, to fix the terminal member 60 to the case lid member 21.
Although detailed description is omitted, the portions of the case lid member 21 to which the terminal fixing resin members 70 are joined and the portions of the terminal members 60 to which the terminal fixing resin members 70 are joined are respectively provided with nano-level nano-roughened portions on which the nanocolumns as described above stand together in large numbers. Thus, the terminal fixing resin members 70 are hermetically joined with strong joining force to the case lid member 21 and the terminal members 60 with the resin material 71 filling gaps between the nanocolumns standing numerously on the nano-roughened portions.
In the battery 1 of this embodiment, the safety valve member 30 including the pressure relief type safety valve portion 31 that fractures and opens when the internal pressure of the case 10 rises is fixed to the case lid member 21 via the valve fixing resin member 40. Since the safety valve member 30 is a separate member from the case lid member 21 and is formed separately from the case lid member 21, the safety valve member 30 of a desired shape can be properly formed without being affected by the thickness ta and material of the case lid member 21. The safety valve member 30 is then fixed to the case lid member 21 via the valve fixing resin member 40, so that the safety valve portion 31 can be easily provided in the case lid member 21.
The valve fixing resin member 40 made of resin is softer than the case lid member 21 made of metal. Therefore, even if distortion occurs in the case lid member 21 when the case 10 is formed by welding the peripheral portion 21f of the case lid member 21 all around to the opening portion 11c of the case body 11, distortion is less likely or unlikely to occur in the safety valve member 30 connected to the case lid member 21 via the valve fixing resin member 40. Thus, in the battery 1, even if distortion occurs in the case lid member 21, there is little distortion in the safety valve member 30, and the adverse influence on the valve opening pressure of the safety valve portion 31, for example, can be reduced.
Furthermore, in this embodiment, the valve fixing resin member 40 is made of the thermoplastic resin material 41, and the safety valve member 30 and the valve fixing resin member 40 constitute the thermal relief type safety valve 45 that opens as the temperature rises. That is, the battery 1 has the pressure relief type safety valve portion 31 and also has the thermal relief type safety valve 45. Thus, the battery 1 can be an even safer battery.
In this embodiment, the nano-level hole surrounding roughened portions 24 on which the nanocolumns 26 stand numerously are provided in the hole surrounding portion 23 of the case lid member 21, and the valve fixing resin member 40 is hermetically joined to the hole surrounding roughened portions 24 with the resin material 41 filling gaps between the nanocolumns 26 standing numerously. Therefore, the seal performance and joining strength between the hole surrounding portion 23 of the case lid member 21 and the valve fixing resin member 40 can be enhanced.
The nano-level valve periphery roughened portions 34 on which the nanocolumns 36 stand numerously are provided in the peripheral portion 33 of the safety valve member 30, and the valve fixing resin member 40 is hermetically joined to the valve periphery roughened portions 34 with the resin material 41 filling gaps between the nanocolumns 36 standing numerously. Therefore, the seal performance and joining strength between the peripheral portion 33 of the safety valve member 30 and the valve fixing resin member 40 can be enhanced.
In this embodiment, a thin aluminum plate having a thickness tb of 500 μm or less is used as the safety valve member 30; therefore, the safety valve portion 31 can be easily and highly accurately formed by press forming. Thus, the battery 1 is equipped with the safety valve member 30 in which the valve opening pressure of the safety valve portion 31 is particularly stable.
Since the case lid member 21 and the safety valve member 30 are separate members, the safety valve portion 31 can be easily and highly accurately press-formed in the safety valve member 30 regardless of the thickness ta of the case lid member 21. Accordingly, the battery 1 is equipped with the safety valve member 30 in which the valve opening pressure of the safety valve portion 31 is particularly stable, even though the case lid member 21 is formed from an aluminum plate with the thickness ta of 600 μm or more.
Next, a method of manufacturing the battery 1 described above will be described (see
Then, in a case roughening step S1 (see
In the portions of the case lid member 21Z which are irradiated with the pulsed laser beam LB, metal (specifically, aluminum) near the surface is melted and further turned into vapor. As the temperature of the vapor then decreases, the vapor turns into the particles 26p of aluminum and aluminum oxide, which are then deposited on the bowl-shaped recesses 25. By intermittently applying the pulsed laser beam LB to the case lid member 21Z while shifting the irradiation position, the particles 26p are deposited and joined together like strings of beads into the form of columns, to form the nanocolumns 26 standing together in large numbers (see
Meanwhile, in a valve roughening step S2 (see
Meanwhile, in a terminal roughening step S3 (see
Then, in a resin molding step S4, with the use of a molding die (not shown), the safety valve member 30 is disposed in the valve hole 21i of the case lid member 21, and the positive and negative terminal members 60 are inserted through the pair of insertion holes 21h of the case lid member 21. Then, the molten resin of the resin materials 41, 71 is injected into each cavity (not shown), so that the valve fixing resin member 40 joined to the case lid member 21 and the safety valve member 30 is insert-molded, and a pair of terminal fixing resin members 70 joined to the case lid member 21 and the positive and negative terminal members 60 is insert-molded.
Then, in an electrode body connecting step S5, the electrode body 50 obtained by stacking the positive electrode sheets 51, negative electrode sheets 52, and separators 53 is prepared, and the terminal extension 60b of the terminal member 60 of the positive electrode is ultrasonically welded to the positive current collector 50c of the electrode body 50. The terminal extension 60b of the terminal member 60 of the negative electrode is also ultrasonically welded to the negative current collector 50d of the electrode body 50. The electrode body 50 is then wrapped with the bag-like insulating holder 7.
Then, in an electrode body housing and case forming step S6, the case body 11 is prepared, the electrode body 50 covered with the insulating holder 7 is inserted into the case body 11, and the opening portion 11c of the case body 11 is closed with the case lid member 21. Then, the opening portion 11c of the case body 11 and the peripheral portion 21f of the case lid member 21 are laser welded hermetically over the entire circumference to form the case 10.
Then, in a pouring and sealing step S7, the electrolyte 5 is poured into the case 10 through the liquid inlet 21k, so that the electrode body 50 is impregnated with the electrolyte 5. Then, the liquid inlet 21k is hermetically sealed with the sealing member 15.
Then, in an initial charging and aging step S8, initial charging is performed on the battery 1. Then, the battery 1 is left to stand for a predetermined time so that the battery 1 is aged. In this manner, the battery 1 is completed.
Next, a modified embodiment of the disclosure will be described (see
In the modified embodiment, too, the case lid member 121 and the safety valve member 30 are separate members. Therefore, the safety valve portion 31 can be easily and highly accurately press-formed in the safety valve member 30 regardless of the material of the case lid member 121. Accordingly, the battery 100 is equipped with the safety valve member 30 in which the valve opening pressure of the safety valve portion 31 is particularly stable, even though the case lid member 121 is made of a metal other than aluminum. The other portions of the battery 100 of the modified embodiment similar to those of the embodiment provide substantially the same effects as those provided by the embodiment.
While the disclosure has been described in the light of the embodiment and the modified embodiment, it is to be understood that the disclosure is not limited to the embodiment and the modified embodiment, but may be applied by making changes as needed, without departing from the principle of the disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2024-003420 | Jan 2024 | JP | national |
