JP2006004730A - Assembled sealing plate and battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance reliability of welding strength in connecting an assembled sealing plate composed of a positive electrode terminal cap, a valve body composed of a disciform metal thin plate which is broken at a prescribed pressure, a ring shaped valve body support plate, and a hat shaped bottom plate to electrically connect the positive electrode terminal cap and a positive electrode of a power generating element, with an electrode plate reed connected to the power generating element. <P>SOLUTION: In the assembled sealing plate, the disciform bottom plate 3 having a plurality of through-holes 3a in the vicinity of the center avoiding the center, a ring shaped stainless plate 5, the valve body 4 composed of the disciform metal thin plate which is broken at the prescribed pressure, a ring shaped PTC element plate 6, and a terminal cap 7 having a through-hole 7a are laminated in this order, and these are integrated by a ring shaped insulating gasket 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery and an assembly sealing plate thereof, in particular, a positive terminal cap, a ring-shaped PTC element plate, a valve body made of a disk-shaped metal thin plate that breaks at a predetermined pressure, a ring-shaped stainless steel plate, and a disk-shaped The present invention relates to an assembly sealing plate which is composed of a bottom plate and is electrically connected to the bottom plate from a power generation element via an electrode plate lead.

  Generally, an assembly sealing plate such as a lithium battery includes a positive electrode terminal cap, a valve body made of a disk-shaped thin metal plate that is broken at a predetermined pressure, a ring-shaped valve body support plate, and a positive electrode terminal cap and a positive electrode of a power generation element. It consists of a hat-shaped bottom plate that is electrically connected. Then, the valve body and the valve body support plate are overlapped on the flange portion of the bottom plate, the flange portion is folded back, the bottom plate, the valve body, and the valve body support plate are integrated, and a through hole is provided in the recess of the terminal cap and the bottom plate. Yes. Then, the power generation element is accommodated in a battery case that also serves as a negative electrode terminal, the assembly sealing plate is attached to the opening of the battery case via a gasket, and the concave portion of the bottom plate of the assembly sealing plate and the positive electrode of the power generation element are connected to the electrode plate. The battery is configured by connecting with leads and caulking the opening of the battery case. The electrode plate lead is connected to the bottom plate by spot welding or the like for electrical connection from the power generation element while avoiding the through hole in the recess. Here, the reliability of the welded part and the sealing plate is ensured by ensuring the thickness of the bottom plate so as not to be plastically deformed by the applied pressure during welding.

A cylindrical lithium primary battery having such a sealing plate structure is described in Patent Document 1, for example. FIG. 4 shows a cross-sectional view of the main part of such a cylindrical lithium primary battery. A battery power generation element 22 is housed inside the battery case 21 in which a positive electrode plate, a separator, and a negative electrode plate are overlapped and wound in a spiral shape. Here, the positive electrode plate is an electrode plate in which a metal core material is filled with manganese dioxide powder or the like, the separator is made of PP (polypropylene), and the negative electrode plate is obtained by processing metallic lithium into a sheet shape. In addition, an organic electrolyte is injected into the battery case 21. As an example, the solvent is PC (propylene carbonate), DME (1,2-dimethoxyethane), and the solute is LiCF ₃ SO ₃ (lithium trifluoromethanesulfonate). Is used. In the upper part of the battery power generation element 22, a valve body 24 made of a thin metal plate for having an explosion-proof mechanism to break at a predetermined pressure at a flange portion of a stainless steel hat-like bottom plate 23 having a through hole 23 a in a recess. The lower part is the one obtained by caulking and integrating the ring-shaped stainless steel plate 25 with a hole 25a in the center, and the ring-shaped PTC element plate 26 is placed on the upper part. A structure in which the positive electrode terminal caps 27 are stacked is configured by caulking the opening of the battery case 21 with an annular gasket 28 sandwiched in a U-shaped cross section. In addition, the electrode plate lead 29 connected to the positive electrode plate is spot-welded at one point or two points in a part of the concave portion so as to avoid the through hole 23a of the hat-shaped bottom plate 23.
Japanese Utility Model Publication No.4-112459

  In the sealing plate structure as described above, for example, when the width of the electrode plate lead is narrow or the thickness of the hat-shaped bottom plate is thin, the number of spot welds is increased in order to improve the reliability of the welding strength, It is preferable to change the position of the welding part from the peripheral part of the bottom plate to the central part. However, if the plate thickness is thin, displacement due to pressurization during welding is large, leading to a decrease in reliability of welding strength, which is not preferable.

As an example, if the thickness of the bottom plate is 0.2 mm, changing the one-point spot welding at the peripheral part to the two-point spot welding at the central part will increase the burden of the pressing force, and will also be hat-shaped It was found that the bottom plate was plastically deformed during spot welding due to an increase in the pressure load due to an increase in the distance from the bottom end of the metal to the central pressure point.

  Therefore, in order to realize the two-point spot welding at the center of the bottom plate without plastic deformation, it has been found that the thickness of the bottom plate should be 0.3 mm or more. The thickness of the folded portion when the valve body support plate is folded back is increased by 0.2 mm, so that the entire bottom plate is increased by 0.3 mm, and the electrode plate lead strongly presses the lower battery power generation element portion. Since this increases the possibility of inducing an internal short circuit between the electrode plates, it is not preferable.

  Therefore, the present invention increases the spot welding location from 1 point to 2 points, for example, without increasing the volume of the sealing plate even if the thickness of the bottom plate is increased from 0.2 mm to 0.3 mm, for example. An object of the present invention is to provide a sealing plate structure that can change the peripheral part from the peripheral part to the central part and a battery using the same.

  In order to solve the above-described conventional problems, the assembly sealing plate of the present invention breaks at a predetermined pressure with a disc-shaped bottom plate having a plurality of through holes in the vicinity of the center, avoiding the center, and a ring-shaped stainless steel plate. A valve body made of a disk-shaped metal thin plate, a ring-shaped PTC element plate, and a terminal cap having a through hole are laminated in this order, and these are integrated by an annular insulating gasket.

  The battery of the present invention includes a battery case that houses a power generation element and also serves as a terminal of one polarity, and an assembly sealing plate that includes an annular insulating gasket in an opening of the battery case, the assembly sealing plate includes: A disc-shaped bottom plate having a plurality of through holes in the vicinity of the center, avoiding the center, a ring-shaped stainless steel plate, a valve body made of a disc-shaped metal thin plate that breaks at a predetermined pressure, and a ring-shaped PTC element plate The terminal cap having a through hole is laminated in this order, and these are integrated by the annular insulating gasket, and the bottom plate and the electrode of the other polarity of the power generation element are connected by the electrode plate lead. It is characterized by becoming.

  When a battery is assembled using such an assembly sealing plate, the bottom plate is formed into a disk shape, and the stainless plate, the valve body, and the PTC element plate are laminated in this order, so the volume of the assembly sealing plate can be reduced. In addition, the reliability of the welding strength with the electrode plate lead can be improved by increasing the thickness of the bottom plate.

  The through-holes in the bottom plate release gas when the internal pressure rises due to gas generation inside the battery. To facilitate this, a hole diameter of 0.5 mm or more is preferable. An electrode plate lead is welded in the vicinity of the center, and a hole diameter of 2 mm or less is preferable in order to secure the welding space. Moreover, the opening of the ring-shaped stainless steel plate to which the bottom plate is bonded is sized so as to surround the projected portion of the through hole of the bottom plate on the stainless steel plate, so that the gas release when the internal pressure rises is more reliable. .

  According to the present invention, even if the thickness of the bottom plate is increased, the volume of the assembly sealing plate is not increased, thereby enabling two-point spot welding in the center portion of the bottom plate, and the bottom plate and the electrode plate lead. A battery with improved welding strength and reliability can be provided.

  Further, depending on the battery, the volume of the assembly sealing plate can be reduced, and the capacity of the battery can be increased by increasing the volume of the battery power generation element in the battery case.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

As one embodiment of the present invention, a cylindrical lithium primary battery will be described. FIG. 1 shows a cross-sectional view of the main part of a cylindrical lithium primary battery according to an embodiment of the present invention. This battery is manufactured as follows. First, a positive electrode plate, a separator, and a negative electrode plate are stacked inside a bottomed cylindrical battery case 1 and wound in a spiral shape, and the battery power generation element 2 having the electrode plate lead 9 connected to the positive electrode plate is accommodated. The negative electrode and the battery case 1 are connected. Here, the positive electrode plate is an electrode plate in which a metal core material is filled with manganese dioxide powder or the like, the separator is made of PP (polypropylene), and the negative electrode plate is obtained by processing metallic lithium into a sheet shape. Next, an assembly sealing plate is prepared as follows. The bottom plate 3 and the ring-shaped stainless steel plate 5 are bonded together by resistance welding or ultrasonic welding, and an aluminum valve body 4 is overlapped on the stainless steel plate 5 and fixed by welding by high frequency heating. The bottom plate 3 is provided with through holes 3a having a diameter of 0.8 mm at eight positions in the center portion, avoiding the center, and the stainless plate 5 is surrounded by a portion where the through holes 3a are projected onto the stainless plate 5. An opening 5a having a diameter of 9 mm is provided. Then, the ring-shaped PTC element plate 6 and the positive electrode terminal cap 7 provided with the through holes 7a are overlapped with each other and inserted into an annular gasket 8 made of an insulating resin to complete an assembly sealing plate. The assembly sealing plate is inserted into the battery case 1 and the end portion of the electrode plate lead 9 connected to the positive electrode plate of the power generating element 2 is spot welded to the bottom plate 3 of the assembly sealing plate at one point or two points. An electrolyte is injected. As an example of the organic electrolyte, PC (propylene carbonate) and DME (1,2-dimethoxyethane) are used as a solvent, and LiCF ₃ SO ₃ (lithium trifluoromethanesulfonate) is used as a solute. Finally, the battery is completed by crimping the opening of the battery case 1 inward.

FIG. 4 is a cross-sectional view of the main part of the conventional sealing plate of this battery. The hat-shaped bottom plate 23 used in the battery is made of stainless steel, and the bottom surface has a diameter of 8 mm and a plate thickness of 0.2 mm. is there. Further, a gas vent hole having a diameter of 4 mm is opened at the center of the bottom plate. The electrode plate lead 29 is spot-welded to a part of the peripheral portion of the bottom plate 23 at a point of 3 kg / cm ² and is electrically connected to the positive electrode terminal cap 27.

(Test 1)
In order to evaluate the welding strength, etc. in the connection between the bottom plate and the electrode plate lead, the electrode plate and the stainless plate are integrated into a hat-shaped bottom plate with the same configuration as a conventional battery, and only the electrode plate lead is simulated. Spot welding was performed.

  5 and 6 show a cross-sectional view of a spot welded portion and a bottom view as seen from the electrode plate lead side in a conventional battery. At this time, since spot welding was performed at one point, there was no deformation due to pressurization, but there was a case where sufficient welding strength was not obtained.

Next, in order to change the one-point spot welding to the peripheral part of the bottom plate of this electrode plate lead to the two-point spot welding to the central part, first, the hole at the central part of the bottom surface is closed with the plate thickness remaining 0.2 mm. Change to the bottom plate, apply a weight of 5 kg / cm ² higher than the applied pressure during spot welding to the center of the bottom plate, and confirm the expected deformation at the time of spot welding. Plastic deformation was observed in the pressure part.

(Test 2)
Therefore, a CAE simulation is performed to obtain a guideline of the plate thickness that is not plastically deformed, and the plate thickness is calculated to be 0.3 mm. With the conventional structure using the same hat-shaped bottom plate, only the plate thickness is 0.2 mm to 0.2 mm. The same pressure test was conducted after changing to 3 mm. In this case, visual plastic deformation could not be found in the pressurizing portion.

  However, in this case, the thickness is increased by 0.2 mm due to the folded structure at the flange portion of the hat-shaped bottom plate, and the height of the entire sealing plate is 0.1 mm in addition to the increase of 0.1 mm in the thickness of the welded portion. 3mm higher. Therefore, the positive lead spot-welded to the bottom plate is not preferable because the risk of inducing a micro short circuit due to the pressure on the lower power generation element is increased.

(Test 3)
Therefore, the thickness of the bottom plate is increased to 0.3 mm, and at the same time, the shape of the bottom plate is reduced to reduce the volume of the sealing plate, and as shown in FIGS. The plate 5 and the aluminum valve body 4 were laminated in this order, and the bottom plate 3 and the stainless steel plate 5 were bonded together by ultrasonic bonding in order to block the leakage path. The bottom plate 3 is provided with through holes 3a having a diameter of 0.8 mm at eight positions in the center portion, avoiding the center, and the stainless plate 5 is surrounded by a portion where the through holes 3a are projected onto the stainless plate 5. An opening 5a having a diameter of 9 mm is provided. By sandwiching the stainless steel plate 5 between the bottom plate 3 and the valve body 4 and leaving a predetermined spatial distance, the influence of pressurization and heating at the time of spot welding becomes difficult to appear on the valve body. With such a configuration, a pressure test similar to that described above was carried out and the degree of deformation was confirmed. As a result, no plastic deformation was observed and the valve body 4 was not torn.

  Then, as shown in FIG. 2 and FIG. 3, a two-point spot welded electrode plate lead 9 was prepared at the center of the flat bottom plate 3, and the initial tensile strength was confirmed, but the strength sufficiently exceeded the current standard. It was possible to confirm that the reliability was improved.

  Next, the battery shown in FIG. 1 was assembled with the same configuration as that shown in FIGS. In the battery of the present invention, since spot deviation in the sampling inspection after battery assembly has been eliminated, the time required for re-inspection and process analysis that has been performed in the past is no longer necessary, greatly contributing to man-hour reduction and productivity improvement. became. In addition, the structure of caulking the stainless steel plate and aluminum valve body with the bottom plate is stopped, and each is flat and integrated with the upper PTC element plate and the positive terminal cap together with the annular insulating gasket. Can be reduced.

  The battery using the battery assembly sealing plate according to the present invention has an electrode plate lead to the center of the bottom plate without increasing the volume of the assembly sealing plate even if the thickness of the bottom plate constituting the assembly sealing plate is increased. By making it possible to perform a plurality of spot welding or ultrasonic welding of the connection, it contributes to the improvement of the reliability of the welded part of the battery more than before.

Sectional drawing of the principal part of the cylindrical lithium primary battery of the Example of this invention Sectional drawing of the state in which the positive electrode lead is spot welded to the bottom plate of the present invention Bottom view of the state where the positive electrode lead is spot welded to the bottom plate of the present invention Sectional view of the main part of a conventional cylindrical lithium primary battery Sectional view of positive electrode lead spot welded to conventional bottom plate Bottom view of positive electrode lead spot welded to conventional bottom plate

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery case 2 Battery power generation element 3 Bottom plate 3a Through-hole (phi0.8mmx8 location)
4 Valve body 5 Stainless steel plate 5a Opening 6 PTC element plate 7 Positive terminal cap 7a Through hole 8 Gasket 9 Electrode plate lead 10 Spot weld (2 points)
21 Battery case 22 Battery power generation element 23 Bottom plate 23a Through-hole (φ4 mm × 1 location)
24 Valve body 25 Stainless steel plate 26 PTC element plate 27 Positive electrode terminal cap 27a Through hole 28 Gasket 29 Electrode plate lead 30 Spot weld (1 point)

Claims (5)

A disc-shaped bottom plate having a plurality of through holes in the vicinity of the center avoiding the center, a ring-shaped stainless steel plate, a valve body made of a disc-shaped metal thin plate that breaks at a predetermined pressure, and a ring-shaped PTC element plate; An assembly sealing plate, wherein terminal caps having through holes are laminated in this order and are integrated by an annular insulating gasket. The assembly sealing plate according to claim 1, wherein the through hole of the bottom plate has an inner diameter of 0.5 to 2 mm. The assembly sealing plate according to claim 1, wherein a projection portion of the through hole of the bottom plate onto the stainless plate is surrounded by the opening of the stainless plate. The assembly sealing plate according to claim 1, wherein the bottom plate and the stainless steel plate are bonded together by resistance welding or ultrasonic welding. A battery case that houses a power generation element and also serves as a terminal of one polarity, and an assembly sealing plate including an annular insulating gasket at the opening of the battery case, the assembly sealing plate is located near the center avoiding the center A disk-shaped bottom plate having a plurality of through holes, a ring-shaped stainless steel plate, a valve body made of a disk-shaped metal thin plate that is broken by a predetermined pressure, a ring-shaped PTC element plate, and a terminal cap having a through-hole In this order, these are integrated by the annular insulating gasket, and the bottom plate and the electrode of the other polarity of the power generation element are connected by an electrode plate lead. .

Images