JP2008262744A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery with a high reliability which can prevent an occurrence of a dislocation (peeling) of a welded portion between a rupture plate (a safety valve) and a terminal plate due to an external shock on the battery. <P>SOLUTION: A projected portion 7B of a rupture plate 7 is welded on a terminal plate 4, and an insulation plate 6 contacting with the rupture plate 7 and a reinforcing plate 5 contacting with the terminal plate 4 are lapped together and inserted around the projected portion 7B between the rupture plate 7 and the terminal plate 4, and an outer circumferential portion 5A of the reinforcing plate 5 is embedded into and fixed with a ring-shaped gasket 3. The reinforcing plate 5 is held tight by the gasket 3 and the reinforcing plate 5 does not move up and down and a force added on a welded portion 11 between the rupture plate 7 and the terminal plate 4 becomes very small, and troubles occurring due to a dropping of the battery or the like, such as a dislocation or a peeling of the welded portion between the rupture plate and the terminal plate, can be prevented at a high level. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a sealed battery, and more particularly to a sealed battery that can prevent detachment (peeling) of a welded portion of a rupture plate and a terminal plate at a very high level caused by an external impact on a terminal plate. .

  Conventionally, secondary batteries such as lithium batteries and carbon lithium batteries have been widely used in cameras, videos, mobile phones and the like.

  Since this type of battery adopts a hermetically sealed configuration, there is a risk of battery explosion if the power generation element housed in the battery undergoes a chemical change and the internal pressure increases. For example, in the case of a lithium secondary battery, when a non-aqueous electrolytic battery is in an overcharged state due to an overcurrent flow, the electrolytic solution decomposes and generates gas. Rapid decomposition of the substance occurs, the temperature in the battery rises, the internal pressure further increases, and the battery is ruptured.

  Therefore, in this type of sealed battery, a safety mechanism is usually provided to prevent the battery from rupturing due to an increase in the internal pressure of the battery as described above. FIG. 2 shows a conventional rupture plate (safety plate) that cuts off the current when the internal pressure of the battery exceeds a predetermined value and partially breaks to prevent the battery from bursting when a further increase in internal pressure occurs. This is an example of a sealed lithium ion secondary battery.

  In this sealed lithium ion secondary battery 50, the opening 1 a of the outer can 1 in which the power generation element 21 is accommodated is formed by the plate group 2 including the terminal plate 8 and the ring-shaped gasket 3 that holds the plate group 2. The sealing structure is formed by sealing.

  The plate group 2 including the terminal plate 8 includes a terminal plate 4, a reinforcing plate 5, an insulating plate 6, a rupture plate 7 and a PTC element 9 in addition to the terminal plate 8. The terminal plate 8, the PTC element 9 and the rupture plate 7 are overlapped on the outer peripheral edge thereof, and covered with the first receiving portion 3 </ b> A of the ring-shaped gasket 3, so that the end of the side wall of the outer can 1 on the opening 1 a side. Caulked and held. On the other hand, the terminal plate 4, the reinforcing plate 5, and the insulating plate 6 are stacked, and their outer peripheral ends extend from the inner peripheral edge of the lower ring plate portion 3 a of the first receiving portion 3 A of the ring-shaped gasket 3 to the power generation element 21 side. It is held by the provided second receiving part (step part) 3B.

  The resistance of the PTC element 9 increases as the temperature rises so that the current is cut off when the temperature exceeds a predetermined value. On the other hand, the rupture plate 7 is formed in a dish shape that bulges toward the power generation element 21 from the outer peripheral edge (flange) held by the first receiving portion 3A of the ring-shaped gasket 3, and the bulge portion A protrusion 7B protruding toward the power generation element 21 is formed at the approximate center of 7A, and the protrusion 7B contacts the terminal plate 4 through the through holes 5a and 6a formed in the insulating plate 6 and the reinforcing plate 5. The terminal plate 4 is welded to the upper surface. Reference numeral 11 denotes a welded portion. On the other hand, a positive electrode tab 10 is welded to the lower surface of the terminal plate 4, and the terminal plate 4 is electrically connected to the power generation element 21 through the positive electrode tab 10.

  The insulating plate 6 is an annular plate made of an insulating material, and is provided so that other portions of the rupture plate 7 except for the protrusions 7 </ b> B are not electrically connected to the terminal plate 4. Further, the reinforcing plate 5 is a metal annular plate material, and the terminal plate 4 is prevented so that the welded terminal plate 4 does not move with the deformation of the rupture plate 7 when the rupture plate 7 is deformed by an increase in internal pressure of the battery. Is held down (power generation element 21 side). That is, for some reason, when gas is generated in the housing portion of the power generation element 21 and the internal pressure rises, the rupture plate passes through the through holes 4a, 5a, 6a formed in the terminal plate 4, the reinforcing plate 5 and the insulating plate 6, respectively. This internal pressure is applied to 7, and as shown in FIG. 3, the rupture plate 7 bulges and deforms toward the terminal plate 8 side. At this time, the terminal plate 4 welded to the protrusion 7 </ b> B of the rupture plate 7 tries to lift, but the terminal plate 4 cannot move due to the presence of the reinforcing plate 5. For this reason, the welding part 11 of the protrusion 7B of the rupture plate 7 to the terminal plate 4 is peeled off, the electrical connection between the terminal plate 4 and the rupture plate 7 is cut off, the current is cut off, and the gas generation is stopped. As a result, an increase in battery internal pressure is suppressed. The groove 7a formed around the protrusion 7B of the rupture plate 7 is used when the internal pressure rises further for some reason even if the electrical connection between the terminal plate 4 and the rupture plate 7 is broken. The rupture plate 7 is provided to prevent the battery 7 from being broken by the groove 7a.

  By the way, in such a conventional sealed lithium ion secondary battery 50, the second receiving portion 3B of the ring-shaped gasket 3 is extended from the inner peripheral edge of the lower ring plate portion 3a of the first receiving portion 3A to the power generation element 21 side. A cylindrical portion 3b and a projecting piece 3c connected to the end of the cylindrical portion 3b. The inner peripheral surface of the cylindrical portion 3b contacts the outer peripheral end portions of the terminal plate 4, the reinforcing plate 5 and the insulating plate 6. At the same time, since the projecting piece 3c directly supports the terminal plate 4, even if an impact is applied to the terminal plate 8 due to a drop of the battery or the like, the terminal plate 4 is not easily moved. A force is applied to the welded portion 11 with the plate 7 so that the welded portion 11 is detached or peeled off, and the electrical connection is not easily broken.

In Patent Document 1, similarly to the above-described sealed lithium secondary battery 50, the ring-shaped gasket is provided with a step for restricting the movement of the metal annular plate (disk) corresponding to the terminal plate 4. Displacement of the welded part of the rupture plate (safety valve) caused by external impact on the terminal plate due to battery dropping etc. by holding the annular plate (disk) at the step (step) It has been proposed to suppress (peeling).
Japanese Patent No. 3555240

  However, as a result of the inventor's research, the above-mentioned gasket is provided with protrusions or steps, and the terminal plate is supported by the protrusions or steps, thereby restricting the movement of the terminal plate. Although it is possible to suppress the detachment (peeling) of the welded part with the rupture plate (safety valve) due to the movement of the terminal plate, even if the movement of the terminal plate itself is restricted, the reinforcement plate moves up and down to force it on the terminal plate. It was found that this force caused the weld between the rupture plate (safety valve) and the terminal plate to come off or peel off. That is, the plate materials (insulating plate, reinforcing plate, terminal plate, etc.) arranged below the rupture plate (around the rupture plate protrusion) are held by the inner peripheral surface of the ring gasket and the protruding piece (step). It was found that the detachment (peeling) of the welded portion of the rupture plate (safety valve) caused by an external impact on the terminal plate could not be sufficiently suppressed only by regulating the movement of the rupture plate.

  The present invention has been made in view of such circumstances, and the problem to be solved is the occurrence of detachment (peeling) of the welded portion between the rupture plate (safety valve) and the terminal plate due to external impact on the battery. To provide a highly reliable sealed battery that can be prevented at a high level.

  As a result of earnest research to solve the above problems, the present inventor has fixed the outer peripheral end of the reinforcing plate in contact with the terminal plate to the ring-shaped gasket, so that a rupture plate (safety valve) when an impact is applied to the terminal plate. ) And the terminal plate were found to be extremely difficult to come off (peel), and the present invention was completed.

That is, the present invention is as follows.
(1) A sealed battery in which an opening of an outer can containing an electric power generation element is sealed by a plate material group including a terminal plate, a rupture plate, and a terminal plate, and a ring-shaped gasket that holds the plate material group,
The plate material group welds a protrusion provided on a rupture plate to a terminal plate, and an insulating plate in contact with the rupture plate and a reinforcing plate in contact with the terminal plate are stacked around the protrusion between the rupture plate and the terminal plate. A sealed battery characterized in that it has a stacked plate structure, and the outer peripheral end of the reinforcing plate is fixed to a ring-shaped gasket.
(2) The sealed battery according to (1) above, wherein the outer peripheral end of the reinforcing plate is embedded in a ring-shaped gasket and fixed.
(3) The sealed battery according to (2) above, wherein the reinforcing plate is insert-molded when the ring-shaped gasket is molded, and the outer peripheral end of the reinforcing plate is embedded in the ring-shaped gasket.

  In the sealed battery of the present invention, since the outer peripheral end of the reinforcing plate is fixed to the gasket, the reinforcing plate is held by the gasket and the reinforcing plate does not substantially move up and down. The force applied to the welded portion of the rupture plate and the terminal plate when impact is applied is greatly reduced, and as a result, the welded portion between the rupture plate (safety valve) and the terminal plate is prevented from coming off and peeling at a higher level than before. can do.

Hereinafter, the present invention will be described in more detail with reference to the drawings.
FIG. 1 is a cross-sectional view of a sealed lithium ion secondary battery according to an example of the present invention. In FIG. 1, the same reference numerals as those in FIGS.

  As shown in the lithium ion secondary battery 100 (FIG. 1) of the example, the sealed battery of the present invention includes a plate material group 2 including a terminal plate 8 and a ring-shaped gasket 3 that holds the plate material group 2. And, it has a sealed structure in which the opening 1a of the outer can 1 containing the power generation element 21 is sealed.

  The outer can 1 is usually composed of a thin iron can body having a bottomed cylindrical shape, and its bottom is usually used as a negative electrode. The plate group 2 includes a terminal plate 4, a reinforcing plate 5, an insulating plate 6, a rupture plate 7 and a PTC element 9 in addition to the terminal plate 8.

  The terminal plate 8 is usually a positive electrode and is made of, for example, an iron-based metal material such as stainless steel, iron, or nickel-plated iron.

  The rupture plate 7 is usually formed of a plate-like member made of aluminum and having a thickness of about 0.1 to 1 mm, and its outer peripheral edge (flange portion) is held by the first receiving portion 3A of the ring-shaped gasket 3. . Moreover, it has the bulging part 7A which bulges in the electric power generation element 11 side, and the protrusion 7B is formed in the approximate center of this bulging part 7A. A circular groove 7a surrounding the protrusion 7B and a plurality of linear grooves (not shown) extending radially from the circular groove 7a are formed on the plate surface on the terminal board 8 side. As with the circular groove 7a, the plurality of linear grooves can cause the battery to rupture when the internal pressure rises further for some reason even if the electrical connection between the terminal plate 4 and the rupture plate 7 is broken. This is a groove that breaks the rupture plate 7 in order to prevent it from reaching, and is provided in addition to the circular groove 7a to make the rupture plate 7 easier to break. These circular grooves 7a and linear grooves are formed so that the plate thickness under the grooves is about 0.01 to 0.1 mm.

  The PTC element 9 is formed of, for example, a plate-like member having a thickness of about 0.1 to 1 mm made of a carbon sheet-dispersed resin sheet with a nickel foil attached to the both sides. A circular through-hole 9a is formed in the bottom.

  The protrusion 7B formed at the approximate center of the bulging portion 7A of the rupture plate 7 is in contact with the terminal plate 4 through the through holes 5a and 6a formed in the insulating plate 6 and the reinforcing plate 5, for example, by laser welding or the like. It is welded to the plate 4 to form a weld 11. That is, between the rupture plate 7 and the terminal plate 4, an annular plate-shaped insulating plate 6 in contact with the rupture plate 7 and a metal ring-plate-shaped contact in contact with the terminal plate 4 are provided around the protrusion 7 B of the terminal plate 4. A stack structure in which the reinforcing plates 5 are inserted in a stacked manner is formed. On the other hand, a positive electrode tab 10 is welded to the lower surface of the terminal plate 4, and the terminal plate 4 is electrically connected to the power generation element 21 through the positive electrode tab 10.

  The configuration of the plate group 2 including the terminal plate 8, the terminal plate 4, the reinforcing plate 5, the insulating plate 6, the rupture plate 7 and the PTC element 9 described above is the same as that of the conventional sealed lithium ion secondary battery 50 described above. Although it is basically the same as that shown in FIG. 1, in the sealed battery of the present invention, when the rupture plate 7 is deformed by an increase in the internal pressure of the battery, the terminal plate 4 welded to the rupture plate 7 is the rupture plate. 7 is characterized in that the outer peripheral end 5A of the annular plate-like reinforcing plate 5 that serves to hold the terminal plate 4 downward (to the power generation element 21 side) so as not to move together with the ring 7 is fixed to the ring-shaped gasket 3.

  The above “adhesion” refers to the contact of the outer peripheral end 5A of the reinforcing plate 5 with the inner surface of the ring-shaped gasket 3 or the step provided on the ring-shaped gasket 3 as in the conventional battery of this type (FIG. 2). As a result of the terminal plate 4 being supported by the part or the like, the outer peripheral end 5A of the reinforcing plate 5 is not fixed, but the terminal plate of the ring-shaped gasket as in the battery 100 (FIG. 1) of the example. 8, a cylindrical portion 3b ′ (second receiving portion 3B) extending from the inner peripheral edge of the lower ring plate portion 3a of the first receiving portion 3A that holds the outer peripheral edge portions of the rupture plate 7 and the PTC element 9 to the power generation element 21 side. This means that the outer peripheral end portion 5A of the reinforcing plate 5 is attached to the ring-shaped gasket 3 in a restrained state, for example, by embedding (embedding and fixing) the outer peripheral end portion 5A of the reinforcing plate 5.

  In the sealed battery of the present invention, as shown in FIG. 1, the insulating plate 6 is placed on the reinforcing plate 5, and the outer peripheral end of the insulating plate 6 contacts the inner surface of the cylindrical portion 3 b ′ of the gasket 3. The terminal plate 4 is inserted (inserted) into the cylindrical portion 3b ′ of the gasket 3 below the reinforcing plate 5, and the protrusion 7B of the rupture plate 7 is welded to the terminal plate 4. Is held by.

  Thus, in the sealed battery of the present invention, since the outer peripheral end 5A of the reinforcing plate 5 is fixed to the gasket 3 and the reinforcing plate 5 is held by the gasket 3, the reinforcing plate 5 does not move up and down. The force applied to the rupture plate 7 when the battery receives an external impact can be made extremely small, and the detachment (peeling) of the welded portion between the rupture plate 7 and the terminal plate 4 can be prevented at a higher level than before.

  In the present invention, when the outer peripheral end 5A of the reinforcing plate 5 is embedded and fixed in the gasket 3 as in the example of FIG. 1, the embedding depth is preferably at least 1.5 mm. If it is less than 1.5 mm, there is a possibility that sufficient fixing force (holding force) of the reinforcing plate 5 cannot be obtained. Moreover, although the reinforcement board 5 is normally comprised with an aluminum plate, it is preferable that thickness is about 0.25-0.3 mm. If the thickness exceeds the range, it is necessary to make the protrusion 7B of the rupture plate 7 longer and the rupture plate 7 may be difficult to bulge and deform toward the terminal plate 8 when the internal pressure rises. If too large, the movement of the terminal plate 4 becomes difficult to be prevented when the rupture plate 7 is deformed due to an increase in internal pressure, which is not preferable.

  In the sealed battery of the present invention, when the outer peripheral edge of the reinforcing plate is embedded and fixed (embedded) in the gasket, the method is not particularly limited. For example, the outer peripheral end of the reinforcing plate is formed on the inner surface of a predetermined portion of the gasket. A groove to be inserted is formed, inserted into the outer peripheral edge of the reinforcing plate in the groove, and fixed with an adhesive (adhesion method), or when forming a ring-shaped gasket, the reinforcing plate is insert-molded, A method of inserting and fixing the outer peripheral end portion of the reinforcing plate in the gasket (insert method) is preferable, but an insert method is more preferable because a stable fixing structure (holding structure) of the reinforcing plate can be easily obtained. Note that polypropylene is usually used for gaskets from the standpoint of heat resistance, etc., but polypropylene shows good adhesion to a reinforcing plate made of an aluminum plate, and the outer peripheral end of the reinforcing plate is firmly adhered to the molded product. Form.

  Further, in the present invention, as a method for fixing the outer peripheral edge of the reinforcing plate to the gasket other than the method for embedding and fixing (embedding) the outer peripheral edge of the reinforcing plate in the gasket, for example, the inner surface of the gasket can be used. On the other hand, a protrusion for supporting the reinforcing plate with the pin raised is formed, and a hole (hole) into which the pin is fitted is provided in the outer peripheral edge of the reinforcing plate, and the outer peripheral edge of the reinforcing plate is formed by fitting between them. And the like, and the like is attached to the protruding piece in a restrained state.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples.
Example 1
A sealed lithium ion secondary battery having the structure of FIG. 1 (cylindrical outer can with an outer diameter of 18 mm and a height of 65 mm: made of aluminum having a thickness of 0.3 mm by insert molding when molding a polypropylene ring-shaped gasket. The outer peripheral edge of the reinforcing plate is fixed to a gasket with a 0.2mm embedding and fixed 24 pieces, and the battery is dropped from a height of 1.5m onto the concrete floor and the bottom of the outer can is directed downward in the vertical direction. The drop test was repeated 15 times.
In the drop test, the electrical resistance value between the terminal plate and the rupture plate after dropping was measured for each drop, and when the resistance value became ∞, it was judged that the welded part was detached (peeling).

(Comparative Example 1)
The sealed lithium ion secondary battery of the conventional structure shown in FIG. 2 (cylindrical outer can as in Example 1; the outer peripheral end of the terminal plate is supported by a protruding piece of 0.25 mm protruding from the lower end of the gasket) Ten pieces were produced and subjected to the same drop test as in Example 1.

(Test results and discussion)
None of the 24 batteries of Example 1 had any detachment (peeling) of the welded parts even after being dropped 15 times. On the other hand, the 10 batteries of Comparative Example 1 are one battery whose electric resistance value between the terminal plate and the rupture plate becomes ∞ after the seventh drop, and the electric resistance between the terminal plate and the rupture plate after the tenth drop. One battery with a value of ∞ was generated. From this result, it was found that the sealed battery of the present invention is a highly reliable battery in which the detachment (peeling) of the welded portion of the rupture plate and the terminal plate against an external impact is prevented at an extremely high level.

1 is a cross-sectional view of a sealed lithium secondary battery according to an example of the present invention. It is sectional drawing of the conventional sealed lithium secondary battery. It is a figure which shows the state which the rupture board act | operated in the battery of FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Exterior can 2 Board material group 3 Ring-shaped gasket 4 Terminal board 5 Reinforcement board 5A Outer peripheral edge 6 Insulation board 7 Rupture board 7B Protrusion 8 Terminal board (positive electrode)
9 Conductive plate 11 Welded part

Claims (3)

A sealed battery formed by sealing an opening of an outer can containing a power generation element by a plate material group including a terminal plate, a rupture plate, and a terminal plate, and a ring-shaped gasket that holds the plate material group,
The plate material group welds a protrusion provided on a rupture plate to a terminal plate, and an insulating plate in contact with the rupture plate and a reinforcing plate in contact with the terminal plate are stacked around the protrusion between the rupture plate and the terminal plate. A sealed battery characterized in that it has a stacked plate structure, and the outer peripheral end of the reinforcing plate is fixed to a ring-shaped gasket.   The sealed battery according to claim 1, wherein an outer peripheral end portion of the reinforcing plate is embedded and fixed in a ring-shaped gasket.   The sealed battery according to claim 2, wherein the reinforcing plate is insert-molded at the time of forming the ring-shaped gasket, and the outer peripheral end portion of the reinforcing plate is embedded in the ring-shaped gasket.

Images