JP4233830B2 - Flat rectangular battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
TECHNICAL FIELD The present invention relates to a flat rectangular battery having a structure that enables a reduction in the thickness of a rectangular battery, and relates to a flat rectangular battery having a structure that prevents the device on which the battery is mounted from being affected by the swelling of a battery case. is there.
[0002]
[Prior art]
Portable electronic devices such as mobile phones and PDAs are becoming increasingly smaller and thinner with higher functionality, and the batteries applied to them are required to be smaller and thinner and have a higher energy density. As a result, demand for flat rectangular lithium-ion secondary batteries is increasing. The recent trend of portable electronic devices is toward thinning rather than downsizing, and since it is easy to put in a pocket or bag and does not impair usability, there are also products that compete for thinning.
[0003]
In order to reduce the thickness of the device, it is required to reduce the thickness of the battery as the power source. However, there is a limit to the reduction in thickness in the battery case manufacturing methods currently in practical use. In other words, the battery case is formed into a bottomed rectangular shape having a rectangular or oval cross-sectional shape by drawing or handling, and the opening of the battery case containing the electrode plate group is sealed by the sealing plate. In order to reduce the thickness, the battery case is formed so that the opening area becomes smaller with respect to the depth in the processing direction. However, as the short side length of the opening shape becomes smaller, processing becomes more difficult, and it becomes difficult to insert the electrode plate group into the battery case. In order to further reduce the thickness of the current flat rectangular battery, it is necessary to fundamentally change the structure of the battery case, and the electrode plate group is accommodated in the recess of the main body case formed in a half shell. A battery structure has been developed in which a main body case is closed by a flat or half-shell lid.
[0004]
For example, a flat shape in which the electrode plate group is accommodated in a container formed in a half-shell, a cover plate is disposed at the opening of the container, and the inside of the container is sealed by laser welding the periphery of the cover plate to the container Is known (see Patent Document 1). The structure in which the large opening of such a half-shell battery case is sealed with a flat plate forms a stepped portion where the battery lid fits into the opening end of the battery case formed in the half-shell, and the electrode plate group Is stored in the battery case, and then the battery case is fitted into the stepped portion, and the battery case and the battery case are laser-welded around the battery case (Patent Document). 2). Further, the electrode plate group is accommodated in the recesses of the pair of half-shell members provided with the collar portion, and the two members accommodating the electrode plate group are sealed by welding both members at the collar portion. A battery is also known (see Patent Document 3).
[0005]
[Patent Document 1]
JP-A-9-213286 (pages 5-7, FIG. 4)
[0006]
[Patent Document 2]
JP 2001-52658 A (pages 5-7, FIG. 1)
[0007]
[Patent Document 3]
Japanese Patent Laid-Open No. 2001-167744 (pages 5-9, FIG. 1)
[0008]
[Problems to be solved by the invention]
However, in the case of a flat rectangular battery, the expansion of the electrode plate causes the battery case that accommodates the battery to swell. In addition, when the battery is exposed to a high temperature environment, or when the temperature becomes high due to an external short circuit or overcharge, the reaction between the positive and negative electrode active materials and the electrolytic solution, decomposition and vaporization of the electrolytic solution occur, and they generate heat. Therefore, the reaction is accelerated and gas is generated, and the battery case is swollen by the increase in internal pressure.
[0009]
In conventional portable electronic devices, etc., a gap is provided between the prismatic battery and the wall of the device in anticipation of the swelling of the prismatic battery, and the swelling of the prismatic battery is absorbed by the gap to affect the device. It is preventing. However, since a useless space for providing a gap in the device is required, the device is prevented from being thinned. If a prismatic battery is installed in a device without providing a gap in order to prioritize thinning, the wall surface of the device in contact with the prismatic battery may be deformed to the outside, or it may contact or apply pressure to the internal components of the device. Sometimes.
[0010]
In the flat prismatic battery pursuing thinning as in the above-described conventional configuration, the battery case has a thin plate thickness, and inferior rigidity such as aluminum or aluminum alloy is used for weight reduction. Since the area occupied by the flat surface becomes large, the battery case tends to swell due to the expansion of the electrode plate and the increase in internal pressure. Further, since the flat battery case has wide flat surfaces on both sides in the thickness direction, the battery case bulges on both sides, making it difficult to form a structure for suppressing the influence.
[0011]
An object of the present invention is to provide a flat prismatic battery provided with a structure that does not affect the bulging of a battery case that is likely to occur in a thin prismatic battery.
[0012]
[Means for Solving the Problems]
The first invention of the present application for achieving the above object is characterized in that a body case is formed in a half-shell having a flange formed around the opening of a recess by processing a metal plate, and the electrode plate group is accommodated in the recess. In a flat rectangular battery formed by welding a metal lid plate and a flange that are arranged with a peripheral portion superimposed on a flange, the battery thickness is reduced on the main body case and / or the lid plate. A depression is formed in the direction , and a heel part is formed around the depression .
[0013]
According to the above configuration, the depression formed in the main body case and / or the cover plate in the direction of decreasing the battery thickness presses the electrode plate group accommodated in the recess so as to compress, so that the electrode plate group expands. When the electrode plate group expands or when the internal pressure of the battery rises, the dent is pushed outward, but by forming the dent formation depth more than the expected amount of bulge, the dent formation depth Since the battery bulges outwardly, the battery thickness hardly changes, and the influence of the battery bulge on the device is suppressed. In addition, since the heel portion is formed around the dent, it is absorbed by deformation of the heel portion that the outward bulge of the dent extends to the main body case and / or the cover plate so that only the dent surface swells. Thus, deformation of the entire battery case is suppressed.
[0014]
Further, in the second invention of the present application, a body case is formed on a half-shell having a flange formed around the opening of the recess by processing a metal plate, and the electrode plate group is accommodated in the recess and the peripheral portion is provided on the flange. In a flat rectangular battery formed by welding between a metal lid plate and a flange that are arranged in a stacked manner, the lid plate has a lower deformation strength than the main body case, and the lid plate A recess is formed in the direction of decreasing the battery thickness , and a heel portion is formed around the recess .
[0015]
According to the above configuration, when the electrode plate group expands or when the battery internal pressure rises, the dent of the cover plate with low deformation strength is pushed outward, but the formation depth of the dent is formed more than the expected amount of bulge. In this case, the thickness of the battery is unlikely to change because the bulge bulges outward within the formation depth of the depression, and the influence on the device due to the swelling of the battery is suppressed. In addition, since the pressure in the bulging direction from the inside of the battery reaches the cover plate side with low deformation strength, it is difficult for the main body case side to bulge. There is no contact or pressure on the internal components. In addition, since the heel part is formed around the dent, it is absorbed by deformation of the heel part that the outward bulge of the dent reaches the entire cover plate, and only the dent surface swells, and the entire battery case Is prevented from deforming.
[0016]
In the above configuration, the deformation strength of the cover plate is reduced by forming the cover plate thinner than the case thickness of the main body case, or by forming the cover plate less rigid than the case of the main body case. Can be made lower than the main body case, and the cover plate side can be deformed by the pressure in the bulging direction from the inside of the battery, and the main body case can be prevented from being deformed.
[0017]
[0018]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, reference examples and embodiments of the present invention will be described with reference to the accompanying drawings to provide an understanding of the present invention. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
[0019]
FIG. 1 shows an external shape of a flat rectangular battery 1 according to a reference example, and is configured as a lithium ion secondary battery. As shown in FIG. 2, the flat rectangular battery 1 includes a main body case 2 formed in a half shell and a cover plate 3 that closes an open portion thereof to form a battery case 50. The electrode plate group 4 is accommodated in the recess 5 of the main body case 2, and the open portion of the main body case 2 is sealed with the lid 3.
[0020]
As shown in FIG. 2, the main body case 2 is formed by pressing a metal plate to form the concave portion 5 provided with the stepped portion 6 and providing a welding allowance 8 in a flange shape around the concave portion 5. The step portion 6 is a portion for forming the positive and negative external connection terminals. Here, the terminal hole 7 formed in the step portion 6 is insulated from the main body case 2 by the outer gasket 11 and the inner gasket 12, and airtightness is ensured. Thus, the rivet 10 serving as the positive electrode external connection terminal is fastened and fixed. Further, an electrolyte inlet 14 is formed in the stepped portion 6.
[0021]
An electrode plate group 4 in which a positive electrode plate and a negative electrode plate are wound via a separator is accommodated in the recess 5 of the main body case 2. The positive electrode lead 15 drawn from the positive electrode plate of the electrode plate group 4 is joined to the rivet 10, and the negative electrode lead 16 drawn from the negative electrode plate is joined to the step portion 6.
[0022]
As shown in FIG. 3, the electrode plate group 4 has different winding directions in which the positive electrode plate and the negative electrode plate are wound via a separator. The positive electrode lead 15 is drawn from the winding end of the positive electrode plate, and the negative electrode lead 16 is The electrode plate group 4a drawn from the winding end of the negative electrode plate can be used, so that the positive electrode lead 15 can be easily joined to the rivet 10 and the negative electrode lead 16 can be joined to the step portion 6.
[0023]
A cover plate 3 is placed on the open portion of the main body case 2 that accommodates the electrode plate group 4, and the peripheral portion of the cover plate 3 and the welding allowance 8 are welded to form the recess 5 of the main body case 2. The inside is sealed by the cover plate 3. The welding method is not particularly limited, and laser welding, electron beam welding, seam welding, ultrasonic welding, and the like can be used. By joining the welding allowance and the cover plate 3, the concave portion 5 can be used. The inside is sealed.
[0024]
A predetermined amount of electrolytic solution is injected into the sealed recess 5 from the electrolytic solution injection port 14, and after the completion of injection, a plug 13 is inserted into the electrolytic solution injection port 14. The inside of the recess 5 is sealed by welding.
[0025]
As shown in FIG. 1, the flat rectangular battery 1 manufactured by the above manufacturing procedure has a rivet 10 formed on the step portion 6 as a positive external connection terminal, and the surface of the step portion 6 serves as a negative external connection terminal. Can be used for. Since the positive and negative external connection terminals are formed on the step portion 6, the leads connected to the external connection terminals can be processed within the thickness of the flat rectangular battery 1. In addition, a contact structure can be formed within the thickness of the flat rectangular battery 1 when contact-connected to the external connection terminal. Therefore, the flat rectangular battery 1 configured to be thin can be mounted on the device without impairing the characteristics.
[0026]
The depression 20 formed in the cover plate 3 constituting the flat rectangular battery 1 having the above-described configuration is formed when the battery case 50 is swollen due to expansion of the electrode plate group 4 or an increase in internal pressure. Absorbing within the depth so as not to cause a change in the thickness of the flat rectangular battery 1, the formation structure of the recess 20 will be described below with reference to FIGS. 4 and 5.
[0027]
FIG. 4 shows a longitudinal section of the battery case 50. The main body case 2 and the lid plate 3 are formed by pressing a metal plate made of the same material. From the calculation formula of the deformation amount of the rectangular plate with four sides fixed at the equally distributed load, the deformation amount of the main body case 2 is δ1, the Young's modulus is E1, the plate thickness is t1, the lid plate 3
(Δ1 / δ2) = (E2 / E1) × (t2 / t1) ³ where δ2 is the deformation amount, E2 is the Young's modulus, and t2 is the plate thickness. When the material of the main body case 2 and the cover plate 3 is the same, if δ1 is suppressed to 0.05 mm and the allowable value of δ2 is 0.40 mm, the plate thickness of the cover plate 3 is ½ of the plate thickness of the main body case 2. It is preferable to make it.
[0028]
The main body case 2 and the cover plate 3 are joined by welding between a welding allowance 8 formed in a flange shape around the main body case 2 and the peripheral portion of the cover plate 3, and the inside of the concave portion 5 of the main body case 2 is formed. Sealed. Although not shown, the flat plate battery 1 is configured by sealing the electrode plate group 4 and the electrolyte in the recess 5 as described above.
[0029]
When the electrode plate group 4 swells due to thermal expansion or aging, the thickness of the flat prismatic battery 1 is exerted by pushing out the planar portion occupying most of the surface area of the main body case 2 and the cover plate 3 outward. May change. Further, when the internal pressure in the recess 5 rises due to decomposition or vaporization of the electrolytic solution when exposed to a high temperature, swelling may occur and the thickness of the flat battery 1 may change. When such a swelling pressure from the inside is applied, the surface of the battery case 50 having the lowest deformation strength is affected.
[0030]
As described above, since the cover plate 3 is formed thinner than the main body case 2, it is possible to prevent the cover plate 3 from being deformed when deformation pressure is applied and the main case 2 to be deformed. . In addition, since the lid plate 3 has a large planar portion, it tends to be deformed to bulge outward when an internal pressure is applied, but a depression 20 is formed in the majority of the center. As a result, the outward bulge of the cover plate 3 reaches the dent 20 and causes the bulge to be arcuate. However, since the swelling occurs within the formation depth of the recess 20, it is possible to prevent the thickness of the flat rectangular battery 1 from changing.
[0031]
As in the embodiment of the present invention shown in FIG. 5, to form a fold region 21 which is uneven formed around the recess 20, as in the case of expansion in the electrode plate group 4 in contact with the cover plate 3 has occurred, the cover plate 3 Even when pressure is applied from the inside to the whole, deformation occurs in the heel portion 21, so that the periphery of the cover plate 3 is not affected, and only the recess 20 bulges outward, and the thickness of the flat rectangular battery 1 is increased. The change can be suppressed more effectively.
[0032]
In the configuration of the reference example and the embodiment described above, the material thickness of the main body case 2 and the cover plate 3 is made different so that there is a difference in deformation strength. However, the rigidity of the plate material constituting the main body case 2 is different. Even if the rigidity of the plate member constituting the cover plate 3 is increased, the deformation strength of the main body case 2 can be increased. From the above-described calculation formula for the deformation amount of the rectangular plate with fixed four sides at the equally distributed load, when the plate thickness of the main body case 2 and the lid plate 3 is the same, δ1 is suppressed to 0.05 mm, and the allowable value of δ2 is 0. When the thickness is 30 mm, it is preferable that the Young's modulus E2 of the cover plate 3 is 1/6 with respect to the Young's modulus E1 of the main body case 2, and when the deformation pressure is applied, the cover plate 3 side is deformed. Can be suppressed.
[0033]
【The invention's effect】
According to the onset bright, even when the increase in the expansion or pressure of the electrode plate group accommodated in the battery case bulging force to the battery case is applied occurs, hardly occurs a change in thickness of the battery, Since the influence on the device due to the swelling of the battery is suppressed, it can contribute to the achievement of thinning of the device.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an external shape of a flat rectangular battery according to a reference example .
FIG. 2 is an exploded perspective view showing each component of the flat rectangular battery.
FIG. 3 is an exploded perspective view showing each component of a flat rectangular battery having a different configuration of an electrode plate group.
FIG. 4 is a longitudinal sectional view of a battery case showing a recess formed in a lid plate.
FIG. 5 is a cross-sectional view showing an embodiment of the present invention .
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Flat rectangular battery 2 Main body case 3 Cover plate 4, 4a Electrode plate group 5 Recessed part 6 Step part 8 Welding allowance 20 Depression 21 襞 part

Claims (4)

A metal case in which a body case is formed in a half-shell body that is formed by processing a metal plate and has a flange around the opening of the recess, and the electrode plate group is accommodated in the recess and the periphery is overlapped with the flange. In the flat rectangular battery formed by welding between the lid plate and the flange made by welding,
A depression is formed in the main body case and / or the cover plate in the direction of decreasing the battery thickness ,
A flat prismatic battery characterized in that a heel part is formed around the depression . A metal case in which a body case is formed in a half-shell body that is formed by processing a metal plate and has a flange around the opening of the recess, and the electrode plate group is accommodated in the recess and the periphery is overlapped with the flange. In the flat rectangular battery formed by welding between the lid plate and the flange made by welding,
The lid plate is formed with a lower deformation strength than the body case, a depression is formed in the lid plate in the direction of decreasing the battery thickness , and a heel portion is formed around the depression. A flat rectangular battery.   The flat rectangular battery according to claim 2, wherein the cover plate is thinner than the main body case.   3. The flat rectangular battery according to claim 2, wherein the lid plate has a smaller rigidity than that of the main body case.

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