JP5379958B2 - battery - Google Patents

Description

  The present invention relates to a battery having a groove portion that is broken when a pressure in a case in which a power generation element is stored rises.

  In recent years, portable electronic devices have become more sophisticated, smaller and lighter, and the use of non-aqueous electrolyte secondary batteries such as lithium-ion batteries has expanded as high-energy density batteries used in these electronic devices. ing. In a nonaqueous electrolyte secondary battery, a power generating element and an electrolytic solution around which a positive electrode plate and a negative electrode plate are wound are stored in a case via a separator, and the case is hermetically sealed.

  By the way, when non-aqueous electrolyte secondary batteries are overcharged beyond specifications or heated beyond specifications, gas is generated inside and the pressure in the case rises above a predetermined value due to the gas. Therefore, as the gas discharge valve, an annular groove that breaks when the pressure in the case rises above a predetermined value is provided in the case, and the internal gas is discharged from the broken portion of the groove, thereby improving the safety of the battery. It is comprised so that it may raise (for example, refer patent document 1).

For example, FIG. 6 is an internal view showing the configuration of a groove portion of a conventional battery, FIG. 7 is a cross-sectional view taken along line VII-VII in FIG. 6, and FIG. 8 is a schematic cross-sectional view showing the configuration of the groove portion. As an annular groove 100 that breaks when the pressure in the case rises above a predetermined value, the groove width H extends from one groove end a to the other groove end b, and from the middle of the groove width H to one groove end a. Further, it is known that the middle part of the groove width H to the other groove end b are formed on the curved surfaces 101, 101 having the same radii R, R.
JP 2004-95457 A

  However, in the conventional battery including the groove portion shown in FIGS. 6 to 8, there is a problem that variation in the rupture operating pressure at the time of rupture is large due to processing variation at the time of forming the groove portion.

  The present invention has been made in view of such circumstances, and the main object is to provide a first curved surface having an appropriate radius from the middle part of the groove width to one groove end, and from the middle part of the groove width to the other groove end. By providing the groove portion having the second curved surface having a radius larger than the radius of the first curved surface, the breakage portion of the groove portion that is broken by the pressure in the case is specified as one of the first curved surfaces, and the variation of the breaking operation pressure is detected. It is an object of the present invention to provide a battery with reduced power consumption.

  Another object of the present invention is to provide a battery in which the variation in the fracture working pressure is further reduced by adopting a configuration in which the second curved surface is formed with a radius that is twice or more the radius of the first curved surface. is there.

Battery according to the first invention, in a case where the power generating element is housed, in a battery pressure within the case is provided by press-forming a groove to break upon rising, the groove is along the groove portion A first curved surface with an appropriate radius from the middle of the groove width to one groove end when viewed from the direction , and a second curved surface with a radius greater than the radius of the first curved surface from the middle of the groove width to the other groove end It has a surface.

In the first invention, when the groove portion formed by press molding is viewed from the direction along the groove portion, the first curved surface having an appropriate radius from the middle portion of the groove width to one groove end , and the groove width The second curved surface having a radius larger than the radius of the first curved surface is provided from the middle part to the other groove end. When such a groove portion is formed, when the groove portion is press-molded in a case made of a metal plate, the stress applied to the second curved surface is more easily dispersed than the stress applied to the first curved surface. Since the stress can be made more difficult to be applied to the second curved surface than the surface, the breakability at the first curved surface is higher than that of the second curved surface, and the groove portion that breaks due to the pressure in the case A fracture location can be specified on one of the first curved surfaces. Furthermore, it is possible to reduce variation in the rupture operating pressure when the groove portion is ruptured. Although it is not clear about the details, it is considered that excessive work hardening of the first curved surface is suppressed by increasing the radius of the second curved surface.

  The battery according to a second aspect is characterized in that, in the first aspect, the second curved surface is formed with a radius that is at least twice the radius of the first curved surface.

  By setting it as such a structure, the variation in fracture | rupture operating pressure can be reduced further.

  According to the first aspect of the invention, it is possible to specify the breakage portion of the groove portion that breaks due to the pressure in the case as one of the first curved surfaces, and thus it is possible to reduce the variation in the break working pressure when the groove portion breaks. It is.

  According to the second aspect of the invention, variation in breaking operating pressure can be further reduced.

  Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof. FIG. 1 is a perspective view showing a configuration of a battery according to the present invention. The battery shown in FIG. 1 is a non-aqueous electrolyte secondary battery in which a power generation element in which a positive electrode plate and a negative electrode plate are wound via a separator and an electrolytic solution are housed in a case 1.

  The case 1 has four side plates connected to the periphery of a rectangular bottom plate, and closes the bottomed case main body 2 having a substantially rectangular parallelepiped shape whose top side is open, and the opening of the case main body 2 being opened. The case body 2 is an external positive electrode.

  The case body 2 is made by press-molding an aluminum plate. The case cover plate 3 is formed by press-molding a relatively thin aluminum plate into a substantially rectangular shape, has a through hole for attaching the negative electrode terminal 4, an oblong shape, and a thin plate portion thinner than the thickness of the case cover plate 3. And the annular groove part 32 hollow in the inner surface of this thin-plate part is shape | molded, and the peripheral part is laser-welded to the case main body 2. FIG.

  2 is an internal view showing the configuration of the groove 32 of the battery, FIG. 3 is a cross-sectional view taken along line III-III in FIG. 2, and FIG. 4 is a schematic cross-sectional view showing the configuration of the groove 32. The groove portion 32 is formed on the inner surface of the thin plate portion 31, and is configured to be broken by the pressure when the pressure in the case 1 rises to a predetermined value or more.

  The groove portion 32 has a groove width H extending over the groove ends a and b that are appropriately separated from each other, and a first curved surface 32a having an appropriate radius R1 is formed from the middle portion of the groove width H to one groove end a. The second curved surface 32b having a radius R2 larger than the radius of the first curved surface 32a, preferably a radius R2 larger than twice the radius R1 of the first curved surface 32a is formed from the midway part to the other groove end b. Thus, when the groove part 32 which has the 1st curved surface 32a and the 2nd curved surface 32b is press-molded, the 1st curved surface 32a and the 2nd curved surface 32b are work-hardened.

  Since the second curved surface 32b shown in FIG. 4 is formed with a radius R2 larger than the radius R1 of the first curved surface 32a, stress applied to the second curved surface 32b is applied to the first curved surface 32a during press molding. It is easier to disperse than the applied stress, and stress is less likely to be applied to the second curved surface 32b than to the first curved surface 32a, so that the breakability at the first curved surface 32a is higher than the second curved surface 32b. Become. By comprising in this way, the fracture | rupture location of the groove part 32 can be specified to the 1st curved surface 32a, and the variation in fracture | rupture operating pressure can be reduced.

  Since the nonaqueous electrolyte secondary battery configured as described above is provided with the groove portion 32 in the case cover plate 3, when the pressure in the case 1 rises to a predetermined value or more due to overcharge or the like, the annular groove portion 32 is broken by the pressure in the case.

[Verification of effect by difference in ratio of radius R1, 2 of first curved surface and second curved surface]
Table 1 shows experimental data obtained by experimenting the relationship between the radii R1 and R2 of the first curved surface 32a and the second curved surface 32b and the rupture operating pressure. In the experiment, the plate thickness t of the case lid 3 is 0.1 mm, the groove width H of the groove 32 is 0.7 mm, the plate thickness h of the groove 32 is 0.03 mm, the radius R1 of the groove 32 is 0.1 mm, and R2 is 0. 1 mm, 0.15 mm, 0.2 mm, and 0.3 mm. The case lid 3 of this size is press-molded, the gas discharge valve portion of the case lid is sealed with a rubber tube, and air is fed until the groove breaks in a state of being fixed by a jig, and the pressure is gradually increased to break the groove. The pressure at the time of the measurement was measured with a pressure gauge, and it was used as the breaking working pressure.

  In Table 1, σ is a standard deviation and indicates an actual variation degree. In addition, C.I. V is a coefficient of variation (σ / average value) and indicates the degree of variation with respect to the average value.

  FIG. 5 is a graph created based on the experimental data in Table 1. As shown in the experimental data shown in Table 1, when the radius R2 of the second curved surface 32b is larger than the radius R1 of the first curved surface 32a, the radius R1 of the first curved surface 32a and the second curved surface 32b. , R2 can be reduced particularly compared to the case where R2 is equal, and by making the radius R2 of the second curved surface 32b larger than the radius R1 of the first curved surface, the variation in the fracture working pressure can be reduced. I understand that.

  Further, as shown in the graph of the experimental data shown in FIG. 5, when the radius R2 of the second curved surface 32b is more than twice the radius R1 of the first curved surface 32a, the values of the standard deviation and the variation coefficient are further increased. It is reduced and becomes almost constant value. Therefore, by setting the radius R2 of the second curved surface 32b to be twice or more the radius R1 of the first curved surface, it is possible to reduce the variation in the fracture operating pressure when the first curved surface 32a of the groove portion 32 breaks. I understand.

  In the embodiment described above, the outer peripheral edge side of the annular groove portion 32 is the second curved surface 32b and the inner peripheral edge side is the first curved surface 32a. In addition, the inner peripheral edge side of the groove portion 32 is the second curved surface. The surface 32b may be used, and the outer peripheral edge may be the first curved surface 32a.

In the embodiment described above, the groove portion 32 is provided on the inner surface of the case cover plate 3, but the groove portion 32 may be provided on the inner surface of the case main body 2. Further, the groove 32 may be provided on the outer surface of the case 1 in addition to the inner surface of the case 1.
Although the groove part 32 of FIG. 2 is an oval annular shape, the shape is not limited as long as the role as a gas discharge valve is not hindered, and examples thereof include a circular shape, an elliptical shape, and a gourd shape.

  Furthermore, in the above embodiment, the average value of the breaking working pressure tended to decrease as the ratio of the radius R2 of the second curved surface 32b to the radius R1 of the first curved surface 32a was increased. The average value of the operating pressure can be adjusted by appropriately changing the thickness of the groove portion 32 and the radii of the first bending portion 32a and the first bending portion 32b.

It is a perspective view which shows the structure of the battery which concerns on this invention. It is an inner surface figure which shows the structure of the groove part of the battery which concerns on this invention. It is sectional drawing of the III-III line | wire of FIG. It is a schematic sectional drawing which shows the structure of the groove part of the battery which concerns on this invention. 3 is a graph created based on the experimental data in Table 1. It is an internal view which shows the structure of the groove part of the conventional battery. It is sectional drawing of the VII-VII line of FIG. It is a schematic sectional drawing which shows the structure of the groove part of the conventional battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Case 32 Groove part 32a 1st curved surface 32b 2nd curved surface R1 Radius of 1st curved surface R2 Radius of 2nd curved surface

Claims (2)

In the battery in which the power generation element is housed, the groove part that is broken when the pressure in the case rises is formed by press molding .
The groove portion has a first curved surface with an appropriate radius from the middle portion of the groove width to one groove end when viewed from the direction along the groove portion , and the first curved surface portion from the middle portion of the groove width to the other groove end. A battery having a second curved surface with a radius larger than the radius.   The battery according to claim 1, wherein the second curved surface is formed with a radius that is twice or more the radius of the first curved surface.

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