JP5673195B2 - battery - Google Patents

Description

  The present invention includes a battery casing formed by fixing a bottomed cylindrical can and a lid, a power generation element housed in the battery casing, and an electrode terminal disposed in the lid. A current cut-off valve that cuts off a current path between the movable part of the valve body, which is a thin plate-like elastic member, as the internal pressure in the battery housing reaches a set pressure, The posture is changed by elastic deformation from a posture protruding inward to the battery housing to a posture protruding toward the outer side of the battery housing, and the valve element is separated from other current path constituent members along with the posture change. The present invention relates to a battery configured to block a path and configured such that an end edge side of the valve body is caulked at an opening end of the can body together with an end edge of the lid portion.

Such a battery includes a current cutoff valve that prevents a further increase in the internal pressure by interrupting the current path in the battery when the internal pressure in the battery casing increases during charging.
As a configuration of this current cutoff valve, roughly two types of basic configurations are considered.
One is to operate the valve body of the current cutoff valve like a disc spring as described in Patent Document 1 below, and FIG. 8A shows the vicinity of the positive electrode of the battery housing in a cross-sectional view. As shown in the figure, a thin plate-like elastic member is provided with a valve body 102 formed in a shape that has a convex posture (the posture shown by a solid line in FIG. 8A) on the inner side of the battery housing 101. As the internal pressure of the body 101 increases, the valve body 102 uses a movement that changes its posture by elastic deformation to a posture that protrudes outward from the battery housing (the posture indicated by a two-dot chain line in FIG. 8A). Break the current path.
In this configuration, the valve body 102 moves in the same manner as a so-called disc spring, and the valve body 102 is subjected to elastic force to maintain the posture in which the valve body 102 is convex toward the inner side of the battery casing. When the internal pressure in the battery casing that presses the outer side of 101 is overcome, the posture of the valve body 102 changes sharply to a position that protrudes outward from the battery casing. That is, in FIG. 8A, the posture shown by the solid line changes sharply from the posture shown by the two-dot chain line.
As another basic configuration, as described in Patent Document 2 below, a relatively thick plate material is used, and as shown in FIG. 8B, the cross section is bent into a stepped shape. Some of them are provided with the valve body 112.
In this configuration, the posture of the valve body 112 gradually changes from the normal posture indicated by the solid line to the posture indicated by the two-dot chain line in FIG. 8B as the internal pressure of the battery casing 111 increases. .
This posture change is basically plastic deformation, although a slight elasticity remains.

JP-A-6-231743 JP 2008-218193 A

When the above two configurations are compared as the operation of the valve body, in the latter configuration, the posture of the valve body gradually changes as the internal pressure of the battery increases, so that the bonding strength between the valve body and other current path constituent members In relation to the above, the variation in the internal pressure of the battery housing in which the current cutoff valve performs the cutoff operation is relatively large.
On the other hand, in the former configuration, when the internal pressure in the battery housing rises, the posture of the valve body changes sharply against the elastic force of the valve body itself, so the current cutoff valve is shut off. The internal pressure of the battery casing to be set can be set with relatively high accuracy.
On the other hand, the former configuration has a difficulty in handling the valve element.
That is, the valve body formed by the elastic member in the former configuration is formed by a considerably thin plate material as compared with the valve body of the latter configuration. Handling when fixed to the end by caulking becomes difficult.
When crimping the lid and the can body, a very large force is applied to deform the valve body, so that a force is applied to compress the valve body toward its center, and the thin valve body itself is deformed by that force. It will be done.

A specific example will be described with reference to FIG. 7 which shows a cross-section by extracting a portion where the valve element 11 of the current cutoff valve CS is attached to the lid portion 2 constituting the battery casing BC. It will be deformed to the post-caulking posture. The deformation | transformation aspect is a deformation | transformation which the surrounding part of the part which elastically deforms in the valve body 11 hangs down.
If the valve body is deformed in this manner, the setting accuracy of the internal pressure in the battery housing in which the current cutoff valve performs a cutoff operation is lowered.
In order to suppress such deformation of the valve body during the caulking work, for example, as shown in FIG. 8A, the lower plate 103 (usually a current path of the battery is configured on the lower side of the valve body 102). A structure that protects the valve body 102 by bending the caulking portion so as to surround the end edge of the valve body 102 and receiving pressure during caulking at the bent portion. It has been.
Thus, by providing the structure for protecting the valve body 102, deformation of the valve body 102 during caulking can be suppressed, but the lower plate 103 is overlaid with the gasket 104 that is an electrically insulating material. As a result, the structure of the caulking portion is complicated, and both side surfaces of the gasket 104 become leakage paths for the electrolytic solution, and the leakage path for the electrolytic solution is increased.
On the other hand, in the latter configuration, in addition to the thickness of the valve body 112 itself, the shape of the valve body 112 has a stepped shape, so that the resistance to pressure during caulking is high. It is also rare that the operating pressure of the current cutoff valve changes sensitively to slight deformation.
The present invention has been made in view of such circumstances, and an object of the present invention is to satisfactorily maintain the operation accuracy of the current cutoff valve while avoiding complication of the structure as much as possible.

  1st invention of this application is arrange | positioned at the battery housing | casing formed by fixing a bottomed cylindrical can and a cover part, the electric power generation element accommodated in the said battery housing | casing, and the said cover part. A current cut-off valve that cuts off a current path between the electrode terminal and the current terminal. As it reaches, the posture changes from the posture that protrudes inward of the battery housing to the posture that protrudes outward of the battery housing by elastic deformation, and the valve body separates from other current path components along with the posture change. In the battery configured to cut off the current path, the edge of the valve body is caulked at the opening end of the can body together with the edge of the lid portion. , At a position separated from the center of the valve body by a set interval, the position and the center Department in sectional view in the vertical direction of the virtual line, a groove-like portion formed in a curved shape or bent shape is disposed in a state surrounding the center.

That is, the valve body of the current cutoff valve is formed of a thin plate-like elastic member, and is arranged so that the shape of the valve body in a normal state is a convex posture toward the inner side of the battery housing. As the internal pressure of the body rises, the current shut-off valve is configured to shut off by suddenly elastically deforming into a posture that protrudes outward of the battery casing.
By adopting such a configuration, there is a problem of deformation of the valve body when the valve body is caulked to the opening end of the can body together with the lid portion, but the valve body has a groove that is curved or bent in a sectional view. By providing the shape portion, when a large force is applied during caulking, the force acting on the valve body is absorbed by the groove portion.
As a result, deformation of the valve body during caulking is suppressed.

Further, in the second invention of the present application, in addition to the configuration of the first invention, the groove-like portion is formed in a state of being thinner than other portions of the valve body.
That is, by reducing the thickness of the groove-like portion, the groove-like portion is easily deformed with respect to an external force.
Therefore, the force acting on the valve body during caulking can be absorbed more efficiently.

According to a third invention of the present application, in addition to the configuration of the first or second invention, the groove-like portion is perpendicular to an imaginary line connecting the position where the groove-like portion exists and the center. It is formed so as to be V-shaped in a cross-sectional view.
That is, various shapes are conceivable as the specific shape of the groove-shaped portion, but as a result of experiments by the inventors of the present application, the deformation of the valve body is effectively suppressed when formed in a V-shaped cross section. I was able to.

According to the first aspect of the present invention, the valve element of the current cutoff valve is projected from the posture protruding inward to the battery casing to the outer side of the battery casing as the internal pressure of the battery casing increases. As a form in which the posture changes sharply due to elastic deformation, while improving the operation accuracy of the current cutoff valve, the groove is formed in the valve body to suppress deformation of the valve body during caulking. Therefore, it is not necessary to separately provide a structure for suppressing the deformation of the valve body, or a simple structure is sufficient even if it is provided.
Therefore, the operation accuracy of the current cutoff valve can be maintained well while avoiding the complexity of the structure as much as possible.
Further, according to the second aspect of the invention, the force acting during caulking can be absorbed more effectively, so that deformation of the valve body during caulking can be further suppressed.
Moreover, according to the said 3rd invention, the deformation | transformation of the valve body at the time of crimping can further be suppressed by making the cross-sectional shape of a high-order groove part into a V shape.

The expanded sectional view of the battery concerning an embodiment of the invention The perspective view of the valve body of the electric current cutoff valve concerning embodiment of this invention Sectional drawing of the valve body of the electric current cutoff valve concerning embodiment of this invention The enlarged view explaining operation | movement of the electric current cutoff valve concerning embodiment of this invention The principal part expanded sectional view concerning embodiment of this invention The graph which shows the experimental result concerning embodiment of this invention The figure explaining the deformation of the valve element of the current cutoff valve The figure explaining the aspect of the conventional current cutoff valve

Hereinafter, embodiments of the battery of the present invention will be described with reference to the drawings.
In the present embodiment, as the battery BT, a secondary battery, more specifically, a lithium ion battery that is a nonaqueous electrolyte secondary battery will be described as an example.
The battery BT has a cylindrical battery casing BC, and the battery casing BC has a bottomed tube as shown in FIG. 1 showing the upper end side (positive electrode terminal side) of the battery BT in a cross-sectional view. It consists of a can body 1 having a shape (more specifically, a bottomed cylindrical shape) and a lid portion 2 arranged so as to cover the opening end of the can body 1.
The lid portion 2 is formed of a metal material that is a conductor and has a substantially disk shape as a whole, but the center portion thereof is formed in a shape that protrudes outward of the battery casing BC, The convex portion is a positive electrode terminal 2a.
In the vicinity of the positive electrode terminal 2a, an opening 2b for discharging gas in the battery casing BC by an operation of a current cutoff valve CS described later is formed.

The current cutoff valve CS includes a valve body 11 and a lower plate 12 as main parts, both of which are formed of a conductive metal material (specifically, aluminum).
The valve body 11 is formed in a substantially dish-like shape as a whole, as shown in FIG. 2 shown in a perspective view and in FIG. 3 shown in a cross-sectional view, as a shape before mounting the thin plate-like aluminum on the battery BT. Yes.
In the central part of the valve body 11, a recessed part 11 a that is a main part of the valve operation is formed, and in the end edge part of the valve body 11, a rising part 11 b is formed. The rising portion 11b is crushed so as to be in a parallel posture with other portions in the process of fixing the lid 2 described later, and has a shape that sandwiches the edge of the lid 2 as shown in FIG. Therefore, the edge side of the valve body 11 is also caulked at the opening end of the can body 1 together with the lid portion 2.
The valve body 11 becomes an elastic member corresponding to a so-called disc spring by forming the recess 11a. Accordingly, even if the posture shown by the solid line in FIG. 1 is pressed from the lower side, the posture of the solid line is maintained by the elastic force, and when the force pressing from the lower side reaches the set pressure, the two-dot chain line Deforms sharply into the posture shown by.

The lower plate 12 as a whole is formed in a disc shape with a plate material thicker than the valve body 11, and a thin-walled portion 12a welded to the lower end of the recessed portion 11a in the valve body 11 is formed at the center thereof. Is formed.
The lower plate 12 is further formed with an opening 12b that is a flow path for discharging gas in the battery casing BC at a position near the edge.
On the lower surface side of the lower plate 12, one end side of a lead 14 made of a metal material as a conductor is fixed at a position below a connection position (welding position) between the valve body 11 and the lower plate 12. Yes.

The lower plate 12 is held by a resinous gasket 13 that is an electrically insulating material and an airtight seal material.
The gasket 13 holds the edge of the lower plate 12, contacts the lower surface side of the valve body 11 at a portion from the holding position of the lower plate 12 toward the radially outer side of the valve body 11, and the edge of the valve body 11 The rising portion 13a is formed in FIG. 2, and the gasket 13 is formed in a donut shape as a whole. The rising portion 13a is interposed between the can body 1 and the rising portion 11b of the valve body 11 to ensure electrical insulation and an airtight seal between them.
The lower surface side of the gasket 13 extends downward in the vicinity of the holding position of the lower plate 12, and the extended portion 13 b is in contact with the insulating plate 15.
A power generation element 16 schematically shown by a one-dot chain line is disposed below the insulating plate 15.
Although a detailed description is omitted, the power generation element 16 is configured by winding a foil-like positive electrode plate and a foil-like negative electrode plate, each coated with an active material, with a separator interposed therebetween. The lead 14 is electrically connected.

In the battery BT having the above-described configuration, when the internal pressure of the battery casing BC increases and reaches a set pressure (for example, 2 MPa), the posture of the movable portion of the valve body 11 (the formation portion of the recessed portion 11a) is as shown in FIG. In FIG. 1, the posture changes from a convex shape toward the inner side of the battery casing BC to a convex posture toward the outer side of the battery casing BC shown in FIG. 1 by elastic deformation.
Along with this change in posture, the lower surface of the recessed portion 11a of the valve body 11 separates from the lower plate 12 which is another current path constituting member.
The detachment between the valve body 11 and the lower plate 12 will be described in more detail based on FIG. 4 showing an enlarged view of the vicinity of the welded portion between the valve body 11 and the lower plate 12.

As shown in FIG. 4A, on the upper surface side of the thin portion 12a of the lower plate 12, a plan view (viewed in the normal direction of the upper surface of the lower plate 12) around the welded portion with the lower surface of the valve body 11 is shown. The ring-shaped V-shaped groove 12c is formed, and when the valve body 11 is detached from the lower plate 12 due to a change in the posture of the valve body 11, as shown in FIG. The location where 12c is formed breaks.
As a mode in which the valve body 11 is detached from the lower plate 12, a configuration in which the valve body 11 and the thin portion 12a are broken at the welded portion may be considered. However, the V-shaped groove 12c is formed as described above, and the formation position is By rupturing, the variation of the operating pressure of the current cutoff valve CS can be suppressed and the operation can be performed with higher accuracy.
That is, when breaking at the welded portion between the valve body 11 and the thin wall portion 12a, it is not easy to suppress variation in the welding strength between the valve body 11 and the thin wall portion 12a. In the configuration in which the groove 12c is broken, the variation in the operating pressure of the current cutoff valve CS greatly depends on the processing accuracy of the V-shaped groove 12c, and such processing can be performed with high accuracy. Variability can be highly suppressed.
The power generation element 16 and the electrode terminal 2a of the lid portion 2 are electrically connected by a current path passing through the lead 14, the lower plate 12, the valve body 11, and the lid portion 2 itself. This current path is interrupted by the separation of.
The current cutoff valve CS also has a function as a so-called rupture valve. When the internal pressure of the battery casing BC rises excessively, the valve body 11 is broken in the posture shown by a two-dot chain line in FIG. The gas in the battery casing BC is discharged to the outside of the battery casing BC through the opening 2b of the lid 2.

When assembling the battery BT having the above-described structure, the lid 2 and the valve body 11 are welded, and the bent portion is encircled by the rising portion 11b of the valve body 11 so as to surround the edge of the lid portion 2. The gasket 13 and the lower plate 12 are assembled, and the thin portion 12a of the lower plate 12 and the lower surface side of the recessed portion 11a of the valve body 11 are welded to form an assembly on the lid portion 2 side. In addition, the welding part of the cover part 2 and the valve body 11 may be anywhere on the surface where the cover part 2 and the valve body 11 are in contact with each other as long as it is not a caulked part. It is preferable to be closer to the center of the valve body than the formed groove portion SC.
On the can body 1 side, the power generation element 16 to which the lead 14 is connected is accommodated in the can body 1, and a process for forming the constricted portion 1 a in the can body 1 is performed.
Next, the lower plate 12 of the assembly on the lid portion 2 side and the end of the lead 14 on the can body 1 side are welded, and the assembly on the lid portion 2 side is covered on the can body 1 side, so that the can body 1 And the rising edge 13a of the gasket 13 is bent together with the opening end of the can body 1, and the opening end of the can body 1 and the end edge of the lid portion 2 are fixed. The electrolytic solution is injected at an appropriate timing before the caulking operation.
During this caulking work, a large force acts on the edge of the valve body 11.
Therefore, when no countermeasure is taken, the valve body 11 is deformed together with the gasket 13 as shown by a two-dot chain line in FIG.

In order to suppress this deformation, a groove portion SC is formed in the valve body 11.
The groove-shaped portion SC is located at a position spaced from the center of the valve body 11 in a cross-sectional view of FIG. 3 or the like, that is, a vertical direction of an imaginary line connecting the position where the groove-shaped portion SC is present In a cross-sectional view (a cross-sectional view in the circumferential direction), a curved shape or a bent shape is formed and arranged in a ring shape so as to surround the center of the valve body 11.
More specifically, when the can body 1 and the lid portion 2 are caulked, the arrangement position of the groove-shaped portion SC is set slightly closer to the center of the valve body 11 than the portion where the caulking force acts. Yes.

Although various shapes can be used as the cross-sectional shape of the groove-shaped portion SC, FIGS. 1 and 3 and the like illustrate the case where a V-shaped cross-section is shown as enlarged in FIG. 5B. ing.
More specifically, the cross-sectional shape shown in FIG. 5B is thinner than the other part of the valve body 11 in a ring shape having a set width including the groove-shaped portion SC.
If it demonstrates with a concrete numerical value, what is necessary is just to set the thickness of the valve body 11 to 0.2 mm-0.4 mm, For example, when the thickness of the valve body 11 is 0.3 mm, it is 0 by press work. Thinner to 2 mm. In the shape shown in FIG. 5B, a V-shaped groove is further formed by pressing or the like after the thinning.

As another example of the cross-sectional shape of the groove-shaped portion SC, as shown in FIG. 5A, the above-mentioned thinning is performed in addition to the same V-shaped cross section that is not thinned as described above. No cross-section with a round shape (FIG. 5C), cross-section with a round shape after thinning (FIG. 5D), no thinning And a cross section having a square shape (FIG. 5E) and a cross section having a square shape after the thinning (FIG. 5D).
Furthermore, the thing of the above-mentioned each cross-sectional shape arranged side by side, and what was made into the waveform shape etc. may be used.

Next, the effect of suppressing deformation of the valve body 11 during caulking work by forming the groove-shaped portion SC in the valve body 11 will be described based on experimental results.
The sample used for the experiment is a cylindrical battery having a diameter of 42 mm and a total length of 91 mm. The thickness of the valve body 11 is 0.3 mm, and the groove-shaped portion SC is formed as shown in FIGS. 5 (a) to 5 (f). Each cross-sectional shape is used.
The groove-shaped portion SC of each cross-sectional shape has a gap “H” between the top of the groove-shaped portion SC and the upper surface of the valve body 11 and a formation width “W1” in the radial direction shown in FIG. H = 0.8 mm and W1 = 1.0 mm.
In the thinning, a 0.3 mm-thick plate material is thinned to a thickness of 0.2 mm by pressing, and the width “W2” in the radial direction of the thinning portion (FIG. 5B) ))), W2 = 1.2 mm.
The formation position of the groove-shaped portion SC of each cross-sectional shape is the distance “D1” in the radial direction between the center of the valve body 11 and the top of the groove-shaped portion SC shown in FIG. 3 and the center of the region pressed by caulking. The position (position indicated by “C” in FIG. 3) and the distance “D2” in the radial direction from the top of the groove-shaped portion SC are set to D1 = 17 mm and D2 = 2.6 mm.
The dimensions of the above parts are numerical examples of the samples used in the experiment, and the present invention can be applied to batteries having various sizes and shapes such as “18650”, “26650”, and “14450” which are general standards. Of course.

About each said shape sample, the distance of the upper end of the positive electrode terminal 2a and the lower surface of the hollow part 11a of the valve body 11 which are shown by code | symbol "L" in FIG.
The measurement results are shown in FIG. This distance “L” has a value (ie, a design value) before caulking work of 4.3 mm, and the deformation amount of the valve element 11 is smaller as the measurement result of the distance “L” is closer to 4.3 mm. Become.
In FIG. 6, the measurement result about the cross-sectional shape of FIG. 5 (a) and FIG.5 (b) is shown as a "V-shaped rib", and the measurement result about the cross-sectional shape of FIG.5 (c) and FIG.5 (d) is shown. Shown as “round ribs”, and the measurement results for the cross-sectional shapes of FIGS. 5 (e) and 5 (f) are shown as “square ribs”, and those that have not been thinned are white circles and thinned, respectively. The black circles indicate what was done.
In the “no countermeasure” at the left end, for comparison, the measurement result when the groove portion SC is not formed is indicated by a white square.

As is apparent from FIG. 6, the deformation of the valve element 11 is small when the cross-sectional shape of the groove-shaped portion SC is V-shaped, and the deformation is particularly small when the groove-shaped portion SC is thinned. ing.
In addition, when the cross-sectional shape of the groove-shaped portion SC is a square shape, the effect of suppressing the deformation of the valve body 11 is not clear when the groove-shaped portion SC is not thinned. The deformation suppressing effect is large.
Further, when the cross-sectional shape of the groove-shaped portion SC is a round shape, the effect of suppressing the deformation of the valve body 11 is clear when the thinning is not performed, but the valve body is obtained by performing the thinning. The effect of suppressing the deformation of 11 is rather small. Although it is not clear about this reason, the effect which suppresses the deformation | transformation of the valve body 11 by a caulking operation | work at least can be confirmed.

[Another embodiment]
Hereinafter, other embodiments of the present invention will be listed.
(1) In the above-described embodiment, the groove-shaped portion SC formed in the valve body 11 is formed as a V-shaped groove that protrudes downward (convex inward of the battery housing BC). You may form in the shape of a convex groove on the outer side of the battery casing BC.
(2) In the above embodiment, the case where the present invention is applied to a lithium ion battery that is a non-aqueous electrolyte secondary battery is exemplified, but some protection means is required against an increase in the internal pressure of the battery casing BC. The present invention can be applied to various types of batteries.

DESCRIPTION OF SYMBOLS 1 Can body 2 Cover part 2a Electrode terminal 11 Valve body 16 Power generation element
BC Battery housing CS Current cutoff valve SC Groove

Claims (3)

A battery case formed by fixing a bottomed cylindrical can and a lid, and a current path between a power generation element housed in the battery case and an electrode terminal disposed in the lid And a current cutoff valve for shutting off,
The current cutoff valve is a thin plate-like elastic member, and the movable part of the valve body protrudes from the position protruding from the inside of the battery housing to the outside of the battery housing as the internal pressure in the battery housing reaches the set pressure. It is configured to change the posture by elastic deformation to a convex posture, and to interrupt the current path by separating the valve body from another current path constituent member along with the posture change,
The battery is configured such that the end edge side of the valve body is caulked at the open end of the can body together with the edge of the lid portion,
A groove-like portion formed in a curved shape or a bent shape in a cross-sectional view in a vertical direction of an imaginary line connecting the position and the center at a position spaced apart from the center of the valve body on the valve body. A battery arranged in a state surrounding the center.   The battery according to claim 1, wherein the groove-like portion is formed in a state of being thinner than other portions of the valve body.   3. The battery according to claim 1, wherein the groove-shaped portion is formed to have a V shape in a cross-sectional view in a vertical direction of an imaginary line connecting the position where the groove-shaped portion exists and the center.

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