This application is based upon and claims the benefit of priority to a Japanese Patent Application No. 2022-086250 filed on May 26, 2022, the entire contents of which are incorporated herein by reference.
The present disclosure relates to a sealed battery.
Japanese unexamined patent application publication No. 2018-041668 discloses a sealed battery including an electrode body, and a metal battery case accommodating the electrode body. The battery case is provided with a rectangular box-shaped case body having an opening, and a metal lid member closing the opening of the case body. The case body and the lid member are integrated together by welding, constituting the battery case. The lid member is provided, at its center, with a safety valve. This safety valve is integrated with the lid member.
The safety valve is thinner than other portions of the lid member and formed with a groove portion on the top surface. Thus, the safety valve actuates when the internal pressure of the battery case reaches a predetermined pressure (i.e., a pressure at which the safety valve opens, hereinafter referred to as a valve opening pressure). Specifically, when the internal pressure of the battery case reaches the valve opening pressure, the groove portion ruptures to open the safety valve, thus releasing gas out of the battery case. This configuration can prevent the internal pressure of the battery case from excessively rising, i.e., from reaching a dangerous internal pressure.
Meanwhile, the foregoing safety valve is integrated together with the lid member made of aluminum. To be concrete, the safety valve is formed in the lid member at the same time of press-molding the lid member from an aluminum plate. However, a method for forming a safety valve in a lid member by the press-molding has limitations on the thickness and the material of a metal plate to be molded into the lid member. This method is therefore difficult to address a wide variety of sealed batteries.
From those circumstances, it has been required to make a safety valve from a different member from a metal wall portion, such as a lid member, that makes up a battery case. Specifically, it has been required that the battery case is formed as a battery case having a metal wall portion formed with a gas vent hole, the safety valve is formed as a safety valve member that closes the gas vent hole. Furthermore, a safety valve member made of resin is demanded for easy production. In other words, a sealed battery has been required in which the gas vent hole formed in the metal wall portion of the battery case is sealed with-a resin safety valve member made of resin, and this resin safety valve member opens when the internal pressure of the battery case reaches the valve opening pressure.
The present disclosure has been made to address the above problems and has a purpose to provide a sealed battery in which a gas vent hole formed in a metal wall portion of a battery case is sealed with a resin safety valve member made of resin, which can open when the internal pressure of the battery case reaches a valve opening pressure.
(1) To achieve the above-mentioned purpose, one aspect of the present disclosure provides a sealed battery comprising: a battery case including a metal wall portion formed with a gas vent hole; and a safety valve member closing the gas vent hole, wherein the safety valve member is a resin safety valve member made of resin, the metal wall portion includes an annular seal surface that surrounds an opening edge of the gas vent hole, the resin safety valve member includes: an annular joined portion hermetically joined to the annular seal surface; and an inside portion located more inside than the annular joined portion in a radial direction, and the inside portion is configured to break when an internal pressure of the battery case reaches a valve opening pressure to open the resin safety valve member.
The above-described sealed battery includes the safety valve member, which closes the gas vent hole formed in the metal lid of the battery case. The safety valve member is a resin safety valve member made of resin. This resin safety valve member includes the annular joined portion hermetically joined to the annular seal surface, which is a part of the metal wall portion and surrounds the opening edge of the gas vent hole. With this annular joined portion, the resin safety valve member is hermetically joined to the metal wall portion, and hence the gas vent hole is sealed with the resin safety valve member.
In this sealed battery, moreover, when the internal pressure of the battery case reaches the valve opening pressure, the inside portion of the resin safety valve member (i.e., the portion located more inside than the annular joined portion in the radial direction) breaks, or ruptures, thus opening the resin safety valve member, that is, releasing the sealing of the gas vent hole sealed with the resin safety valve member. To be concrete, when the internal pressure of the battery case reaches the valve opening pressure, the stress caused in the inside portion of the resin safety valve member by the internal pressure of the battery case reaches a breaking strength of the inside portion, thereby breaking, e.g., rupturing, the inside portion and thus releasing the gas vent hole from sealing by the resin safety valve member. Accordingly, the inside of the battery case is maintained hermetic with the annular joined portion of the resin safety valve member hermetically joined to the annular seal surface of the metal wall portion, whereas once the internal pressure of the battery case reaches the valve opening pressure, the resin safety valve member opens, releasing the gas out of the battery case to prevent the internal pressure of the battery case from excessively rising. As described above, the foregoing sealed battery is a sealed battery in which
the gas vent hole formed in the metal wall portion of the battery case is sealed with the resin safety valve member made of resin and further the resin safety valve member opens when the internal pressure of the battery case reaches the valve opening pressure.
(2) In the sealed battery described in (1), furthermore, the annular seal surface is an annular roughened surface having an uneven shape with pits and protrusions, and the resin safety valve member is hermetically joined to the annular roughened surface by the annular joined portion made of part of the resin forming the safety valve member, the part of the resin forming the annular joined portion entering into the pits of the annular roughened surface.
In the foregoing sealed battery, the annular joined portion of the resin safety valve member is hermetically joined to the annular roughened surface having an uneven shape with pits and protrusions by entering or penetrating of the resin that forms the annular joined portion into the pits of the annular roughened surface of the metal wall portion. In other words, the annular joined portion of the resin safety valve member is hermetically joined to the annular roughened surface by the anchor effect exerted by biting of the protrusions of the annular roughened surface of the metal wall portion into the annular joined portion of the resin safety valve member. This can enhance the hermeticity between the annular joined portion of the resin safety valve member and the annular roughened surface of the metal wall portion and hence increase the hermeticity of the sealed battery.
(3) In the sealed battery described in (1) or (2), furthermore, the inside portion includes a thinnest portion, which is a part of the inside portion and has a thinnest thickness in the inside portion, and the thinnest portion breaks when the internal pressure of the battery case reaches the valve opening pressure to open the resin safety valve member.
In the foregoing sealed battery, the inside portion of the resin safety valve member is not constant in thickness, i.e., wall thickness and includes the thinnest portion with a smallest thickness in the inside portion. Therefore, the valve opening position, where the inside portion is to break when the internal pressure of the battery case reaches the valve opening pressure, can be set at that thinnest portion. This configuration can set the valve opening pressure with high accuracy. The thus configured sealed battery is a sealed battery with accurately set valve opening pressure.
(4) In the sealed battery described in (3), furthermore, the valve opening pressure is determined by a thickness of the thinnest portion.
Since the inside portion of the resin safety valve member includes the thinnest portion, this thinnest portion can be determined as a valve opening position, where the inside portion is to break when the internal pressure of the battery case reaches the valve opening pressure. Further, adjusting the thickness of the thinnest portion enables control of the valve opening pressure. This is because the breaking strength of the thinnest portion depends on the thickness of the thinnest portion. Hence, the valve opening pressure of the above-described sealed battery is determined by the thickness of the thinnest portion. Since the valve opening pressure thus is determined by the thickness of the thinnest portion, the valve opening pressure can be set with high accuracy. This sealed battery is a sealed battery with an accurately set valve opening pressure.
(5) In the sealed battery described in (3) or (4), the inside portion may include a groove, and the thinnest portion may be a bottom of the groove.
Since the inside portion of the resin safety valve member is provided with the groove as the thinnest portion, the valve opening position, where the inside portion is to break when the internal pressure of the battery case reaches the valve opening pressure, can be set at the bottom of the groove. This configuration can set the valve opening pressure with high accuracy. The thus configured sealed battery is a sealed battery with accurately set valve opening pressure.
(6) In the sealed battery described in (5), the groove may be located in a position where the central axis of the annular joined portion passes through the bottom of the groove.
Since the groove is provided so that the central axis of the annular joined portion passes through the bottom of the groove, the internal pressure of the battery case, that is, the valve opening pressure, when the bottom of the groove is to break can be set with high accuracy. Therefore, this sealed battery is a sealed battery with an accurately set valve opening pressure.
A detailed description of an embodiment of this disclosure will now be given referring to the accompanying drawings. A sealed battery 1 in the present embodiment is a lithium-ion secondary battery and includes a battery case 30, an electrode body 50 accommodated in the battery case 30, a positive terminal 41, and a negative terminal 42 (see
The metal lid 11 has two through holes 16 and 17 each having a rectangular tubular shape as shown in
The electrode body 50 includes positive electrode sheets 60, negative electrode sheets 70, and separators 80 each interposed between the positive electrode sheet 60 and the negative electrode sheet 70. More concretely, the electrode body 50 is a lamination electrode body provided with a plurality of positive electrode sheets a plurality of negative electrode sheets 70, and a plurality of separators 80, in which the positive electrode sheets 60 and the negative electrode sheets 70 are alternately laminated, or stacked, with the separators 80 each interposed therebetween in a lamination direction DL as shown in
The metal lid 11 (concretely, the metal wall portion 15) includes an annular seal surface 14 having a circular annular shape surrounding the opening edge 12b of the gas vent hole 12 as shown in
Furthermore, the sealed battery 1 is provided with a resin safety valve member 18 for closing the gas vent hole 12 of the metal lid 11 (concretely, the metal wall portion 15). This resin safety valve member 18 has a closed-bottom cylindrical shape with a flange, including an annular joined portion 18b hermetically joined to the annular seal surface 14 and an inside portion 18c located more inside than the annular joined portion 18b in a radial direction of the resin safety valve member 18, as shown in
The resin safety valve member 18 may be made of a resin with low permeability to an electrolytic solution, for example, polyphenylene sulfide (PPS), polyarylene sulfide (PAS), olefin resin, or fluororesin. In the present embodiment, the resin safety valve member 18 is made of PPS.
The resin safety valve member 18 includes an annular joined portion 18b hermetically joined to the annular seal surface 14 as shown in
In the present embodiment, especially, the annular seal surface 14 of the metal lid 11 (concretely, of the metal wall portion 15) is an annular roughened surface 14 having an uneven shape with pits 14b and protrusions 14c as shown in
The annular roughened surface 14 can be formed by a well-known surface roughening treatment applied to the hole-surrounding surface 13 of the outer surface 11b of the metal lid 11. This treatment may include for example a laser surface treatment, a sandblasting treatment, and an anodizing treatment. One example of the laser surface treatment is disclosed in Japanese unexamined patent application publication No. 2022-028587. In the present embodiment, the hole-surrounding surface 13 of the metal lid 11 is roughened by the laser surface treatment to form the annular roughened surface 14.
The metal lid 11 and the resin safety valve member 18 are integrated by insert molding. Specifically, the metal lid 11 and the resin safety valve member 18 are insert-molded to form a lid 10 equipped with a safety valve, hereinafter referred to as a safety valve-equipped lid 10, which is an insert molded product including the metal lid 11 integrated with the resin safety valve member 18 as shown in
By use of the safety valve-equipped lid 10 including the metal lid 11 and the resin safety valve member 18 integrated together by insert molding, the sealed battery 1 can be easily and appropriately manufactured with the gas vent hole 12 of the metal lid 11 sealed with the resin safety valve member 18. It is noted that a part of the resin injected to mold the resin safety valve member 18, that is, a resin forming the annular joined portion 18b, enters into the pits 14b of the annular roughened surface 14 of the metal lid 11, so that the annular joined portion 18b of the resin safety valve member 18 is hermetically joined to the annular roughened surface 14 of the metal lid 11 shown in
In the sealed battery 1, moreover, when the internal pressure of the battery case 30 reaches the valve opening pressure, the inside portion 18c of the resin safety valve member 18 breaks, e.g., cleaves, to open the resin safety valve member 18. More specifically, when the internal pressure of the battery case 30 rises due to the generation of gas in the battery case 30, the force that pushes upward a lower surface 18g of the resin safety valve member 18 (concretely, the lower surface 18g of the inside portion 18c) becomes larger, and thus the stress occurring in the inside portion 18c becomes larger (see
In the sealed battery 1, specifically, the inside portion 18c of the resin safety valve member 18 is not constant thickness, or wall thickness, and a part of the inside portion 18c, that is, a second portion 18k, is formed as a thinnest portion 18h having a smallest thickness in the inside portion 18c. The inside portion 18c consists of a first portion 18j of a cylindrical shape extending in the thickness direction of the metal lid 11, i.e., in a vertical direction in
Since the valve opening position where the inside portion 18c is to break when the internal pressure of the battery case 30 reaches the valve opening pressure is determined to the thinnest portion 18h, which is a part of the inside portion 18c, the valve opening pressure can be set with high accuracy. The sealed battery 1 is thus a sealed battery with the accurately set valve opening pressure.
As described above, the sealed battery 1 in the present embodiment is configured such that the annular joined portion 18b of the resin safety valve member 18 is hermetically joined to the annular seal surface 14 of the metal lid 11 (concretely, of the metal wall portion 15) to maintain the hermeticity of the battery case 30, whereas once the internal pressure of the battery case 30 reaches the valve opening pressure, the resin safety valve member 18 opens to release the gas out of the battery case 30 in order to prevent the internal pressure of the battery case 30 from excessively rising. Thus, the sealed battery 1 is achieved as a sealed battery in which the gas vent hole 12 of the metal wall portion 15 of the battery case 30 is sealed with the resin safety valve member 18 made of resin, and further the resin safety valve member 18 opens when the internal pressure of the battery case 30 reaches the valve opening pressure.
Meanwhile, the valve opening pressure of the resin safety valve member 18 can be controlled by adjusting the thickness of the thinnest portion 18h of the resin safety valve member 18, i.e., the thickness of the valve opening position of the resin safety valve member 18. This is because the breaking strength of the thinnest portion 18h is different depending on the thickness of the thinnest portion 18h. The valve opening pressure of the resin safety valve member 18 corresponds to the internal pressure of the battery case 30 at which the thinnest portion 18h of the resin safety valve member 18 breaks to release the sealing of the gas vent hole 12.
In the sealed battery 1 in the present embodiment, in this respect, the valve opening pressure of the resin safety valve member 18 is determined by the thickness T of the thinnest portion 18h. Since the valve opening pressure is thus set by the thickness T of the thinnest portion 18h, the valve opening pressure can be accurately set. Consequently, the sealed battery 1 is a sealed battery with the accurately set valve opening pressure.
Table 1 shows the correspondence relationship between the thickness T (mm) of the thinnest portion 18h and the valve opening pressure (MPa). For example, as shown in Table 1, for a sealed battery 1 with the thinnest portion 18h having a thickness T of 0.06 mm, the valve opening pressure can be set to 1.4 MPa. For another sealed battery 1 with the thinnest portion 18h having a thickness T of 0.10 mm, the valve opening pressure can be set to 2.0 MPa. For another sealed battery 1 with the thinnest portion 18h having a thickness T of 0.15 mm, the valve opening pressure can be set to 2.7 MPa. In this way, the valve opening pressure of the resin safety valve member 18 can be determined by the thickness T of the thinnest portion 18h of the resin safety valve member 18.
The present disclosure is described in the above embodiment, but is not limited thereto. It should be understood that the present disclosure may be embodied in other specific forms without departing from the essential characteristics thereof.
For example, the above-described embodiment adopts the safety valve-equipped lid 10 provided with the metal lid 11 and the resin safety valve member 18 integrated together by insert molding. However, the safety valve-equipped lid 10 may be a safety valve-equipped lid provided with the metal lid 11 and a resin safety valve member made of a resin film welded to the metal lid 11. This safety valve-equipped lid can be produced as below. Specifically, the metal lid 11 with the annular roughened surface 14 (see
The second portion 18k of the inside portion 18c of the resin safety valve member 18 may be formed with a groove so that the bottom of this groove is a thinnest portion. Therefore, the bottom of the groove can be determined as the valve opening position where the inside portion 18c is to break when the internal pressure of the battery case 30 reaches the valve opening pressure. Accordingly, the valve opening pressure can be set accurately.
The groove may be formed at a position where the central axis of the annular joined portion 18b, which coincides with the central axis of the gas vent hole 12, passes through the bottom of the groove. In other words, the groove may be formed so that its bottom extends intersecting with the central axis of the annular joined portion. This configuration enables accurate setting of the internal pressure of the battery case when the bottom of the groove is to break, that is, the valve opening pressure.
The above-described embodiment exemplifies the sealed battery 1 in which the gas vent hole 12 is formed in the metal wall portion 15 of the metal lid 11 and closed with the resin safety valve member 18. As an alternative, however, the present disclosure includes a sealed battery in which a gas vent hole is formed in a metal wall portion of the case body 21 and closed with a resin safety valve member.
Number | Date | Country | Kind |
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2022-086250 | May 2022 | JP | national |