JP5309434B2 - Thin battery - Google Patents

Description

  The present invention relates to a thin battery used as a power source for a hybrid vehicle.

  Regarding a thin battery, a thin battery including a power generation element in which a plurality of electrode plates each having a positive electrode plate and a negative electrode plate are stacked via a separator is known. The thin battery is being researched and developed as a secondary battery for automobiles such as a lithium ion secondary battery.

  The power generation element of this thin battery is accommodated between two laminated films as an exterior body, and the outer peripheral edge portions of these laminate films are welded together, thereby sealing the power generation element together with the electrolyte inside the exterior body. It has stopped.

  In such a thin battery in which the power generation element is sealed inside the exterior body, the power generation element generates heat and gas is generated due to overcharge or internal short circuit, and this gas generation causes the inside of the exterior body. A case where the pressure increases is conceivable. If the gas is suddenly released from the exterior body due to an increase in the internal pressure of the exterior body, the internal electrolyte may scatter and affect the electrical equipment around the battery. When the internal pressure increases, it is desirable that the internal pressure can be quickly reduced by a safety valve or the like.

  In order to reduce the internal pressure of the exterior body, a weak part with weak peel strength is provided at a part of the outer peripheral edge of the laminate film constituting the exterior body as a safety valve part. When the internal pressure increases, this safety valve It has been considered that the gas inside the battery is led out to the outside by opening the part with internal pressure (for example, Patent Document 1).

In order to operate the safety valve with high accuracy, it has been proposed to provide a safety member made of a low melting point resin with a transmission member that transmits heat from the power generation element (for example, Patent Document 2).
JP 2003-132868 A JP 2005-116474 A

  However, as described in Patent Document 1, in a battery in which a weak portion having a weak peel strength is provided in a part of the welded portion on the outer peripheral edge of the outer package, the welded portion during normal use (normal time) of the battery is used. It is necessary to set the peel strength so that the peel strength is peeled off when there is an abnormality such as overcharge or internal short circuit while ensuring a sufficient peel strength, but it is difficult to adjust the peel strength of this fragile part and the intended internal It was difficult to surely peel the fragile part with pressure.

  Further, as disclosed in Patent Document 2, the battery provided with the transmission member has a problem that the cost increases due to the provision of the heat transfer member.

The thin battery of the present invention that advantageously solves the above problems has a positive electrode plate and a negative electrode plate as electrode plates, and has a planar separator larger than these electrode plates, and these positive electrode plate and negative electrode A power generation element formed by laminating a positive electrode plate and a negative electrode plate through a separator with a distance between the outer peripheral edge of the plate and the outer peripheral edge of the separator. In a thin battery that seals the inside of an exterior body having a welded portion welded at a predetermined welding width to each other, and peels off the welded portion and opens the exterior body when the power generation element generates heat above a predetermined value. Provided in a part of the outer peripheral edge of at least one of the separator and electrode plate of the power generating element is a portion where the distance between the separator outer peripheral edge and the outer peripheral edge of the electrode plate is shorter than other parts. , At the time of the abnormality , The separator by heat generation of the power generating element is thermally contracted, and summarized in that the other shorter portions than sites were configured to internal short circuit quickly preferentially than the other sites.

  According to the thin battery of the present invention, it is possible to quickly and surely mitigate an increase in internal pressure when an abnormality occurs.

  Embodiments of the thin battery of the present invention will be specifically described with reference to the drawings. FIG. 1 is a plan view of a thin battery 10 according to the first embodiment of the present invention. FIG. 2 is an enlarged perspective view of the region A of the thin battery 10 shown in FIG.

  A thin battery 10 shown in FIG. 1 has a power generation element 11. The power generation element 11 is accommodated in an exterior body 12 made of two laminated films together with an electrolytic solution. The power generation elements 11 are connected to the positive electrode terminal 13 and the negative electrode terminal 14, respectively. The outer peripheral edge of the laminate film of the outer package 12 is welded in such a manner that the positive electrode terminal 13 and the negative electrode terminal 14 extend from the outer package 12 to the outside. It is sealed by.

  The power generation element 11 includes a positive electrode plate 111a in which a positive electrode active material or the like is applied and formed on the surface of the metal foil, a negative electrode plate 111b in which a negative electrode active material or the like is applied and formed on the surface of the metal foil, and the positive electrode plate 111a and And a separator 112 made of a resinous porous sheet interposed between the negative electrode plates 111b. A plurality of these positive electrode plates 111a, negative electrode plates 111b, and separators 112 are alternately stacked to form the power generating element 11. Regarding the size relationship between the separator 112 and the positive electrode plate 111a and the negative electrode plate 111b as electrode plates, the separator 112 has a larger planar shape. As an example, the separator 112 is the same as or larger than the negative electrode plate 111b and larger in size than the positive electrode plate 111a. The power generation element 11 formed by stacking the separator 112 and the electrode plates 111a and 111b having such a size relationship includes an outer peripheral edge portion of the positive electrode plate 111a or the negative electrode plate 111b, and an outer peripheral edge portion of the separator 112. The predetermined distance is open.

  The thin battery 10 according to the present embodiment shown in FIG. 1 includes an outer peripheral edge portion of the separator 112 and a part of at least one outer peripheral edge portion of the separator 112 and the electrode plates 111a and 111b in the power generation element 11. The part which made the distance with the outer-periphery edge part of electrode plate 111a, 111b shorter than another site | part is provided. More specifically, in FIG. 1, a notch 111n is formed in the vicinity of the center of one long side of the separator 112 having a substantially rectangular planar shape.

  As shown in FIG. 2 by enlarging the region including the notch 112n, in the present embodiment, the separator 112 is more than the outer peripheral edge of the positive electrode plate 111a and the negative electrode plate 111b constituting the electrode plate of the power generation element 11. The outer peripheral edge of the outer body 12 extends toward the welded portion of the exterior body 12, and a notch 112 n is formed in a part of the region where the separator 112 extends. The cutout portion 112n has a smaller amount of extension than other portions. That is, the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate is shortened.

  FIG. 3 is a perspective view showing the positional relationship of the overlap between the separator 112 having the notch 112n and the positive electrode plate 111a and the negative electrode plate 111b as electrode plates. As shown in FIG. 3, the power generation element 11 is provided with a separator 112 so as to be interposed between a positive electrode plate 111a and a negative electrode plate 111b having a substantially rectangular planar shape. A notch 112n is formed in a part of the long side of the separator, and the notch 112n is positioned so as to slightly extend from the outer peripheral edges of the positive electrode plate 111a and the negative electrode plate 111b. It has become. The actual power generation element 11 is a laminated body in which the positive electrode plate 111a, the negative electrode plate 111b, and the separator 112 are integrated.

  The effect of the thin battery of this embodiment which has the notch part 112n in the separator 112 of the electric power generation element 11 is demonstrated. When the battery generates heat during an abnormality such as overcharge or dead short, the porous separator 112 is thermally contracted. Then, the distance between the outer peripheral edge of the separator 112 and the outer peripheral edge of the positive electrode plate 111a or the negative electrode plate 111b disappears in the notch portion 112n of the separator 112, and the positive electrode plate 111a and the negative electrode plate 111b become the notch portion. At 112n, the internal short circuit is preferentially performed earlier than other parts. Due to this internal short circuit, current concentrates only in the notch 112n and its vicinity, and heat is rapidly generated at a high temperature. Accordingly, the two portions of the exterior body that are opposed to the notch 112n are heated and softened by the heat generation in the notch portion 112n and the vicinity thereof, and are overlapped and welded to form the exterior body. Since the welding power of the laminate film decreases, the outer package is opened at this site. That is, the welded portion of the exterior body at a portion facing the notch 112n of the separator 112 serves as a safety valve. From this, it is possible to sufficiently secure the peel strength of the laminate sheet at normal time when no abnormality has occurred in the battery, and at the time of abnormality such as overcharge or dead short, the part of the exterior body facing this 112n, Since the package is surely preferentially opened, the exterior body can be reliably opened when the battery is abnormal. Moreover, since the battery of this embodiment can implement | achieve an effect mentioned above only by forming notch part 112n in a part of outer peripheral part of a separator, it is necessary to provide a special heat-transfer member. Absent. The notch 112n can be easily formed by punching or the like, for example, at the time of manufacturing the separator. Therefore, it is not necessary to add a special process to form the notch 112n, and the manufacturing cost is reduced. Does not bring rise.

  In the thin battery 10 of the present embodiment shown in FIGS. 1 to 3, the notch 111n is provided in the central portion on the long side of the separator 112 having a substantially rectangular planar shape. The position of the part is not limited to the illustrated example. In short, it is only necessary to provide a notch in a part of the outer peripheral edge of the separator 112 so that the positive electrode plate 111a and the negative electrode plate 111b can be preferentially short-circuited and generate heat in the event of an abnormality. The position of the notch is not limited. However, providing the notch 112n on the long side as shown in the drawing is advantageous in that there is no interference with the electrode terminal 13 or 14.

  Further, the distance between the outer peripheral edge of the notch 112n and the outer peripheral edge of the positive electrode plate 111a or the outer peripheral edge of the negative electrode plate 111b, which is shortened by forming the notch 112n, is determined by the material of the separator 112, the separator Based on the area and the like, it can be appropriately determined as a value that can be preferentially short-circuited at the notch 112n in the event of an abnormality.

  In the illustrated notch 112n, the planar shape of the notch is trapezoidal, but the planar shape of the notch is not limited to a trapezoidal shape. For example, it may be semicircular or triangular. In addition to the notches, by forming a hole in the vicinity of the outer peripheral edge of the separator 112, the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate can be reduced.

  In the first embodiment illustrated in FIGS. 1 to 3, the structure of the exterior body 12 has the same structure as that of a conventionally known exterior body. The structure of the exterior body 12 can also be devised corresponding to the fact that the separator 112 has the notch 112n.

  An example of a thin battery in which the exterior body 12 is devised is shown in FIGS. 4 is a plan view of the thin battery 20, and FIG. 5 is an enlarged perspective view of a region B in FIG. 4 and 5, the same members as those in FIGS. 1 to 3 are denoted by the same reference numerals, and redundant description is omitted below.

  The thin battery 20 of the present embodiment shown in FIGS. 4 and 5 has a welding width of two laminated films at a portion of the exterior body 12 at a position facing the notch 112 n of the separator 112 of the power generation element 11. It is narrower than the welding width of other parts. As shown in an enlarged view of this region A in FIG. 5, the welding width of the portion facing the notch 112 n in the welded portion of the exterior body 12 close to the separator 112 is the welded portion of the other portion. A narrow portion 12n that is narrower than the width is formed.

  By forming the narrow width portion 12n, the positive electrode plate 111a and the negative electrode plate 111b are located at the position of the notch 112n due to the thermal contraction of the separator 112 when the power generation element 11 generates heat. When the internal short circuit preferentially generates heat, the narrow width portion 12n is easier to open because the welding width is narrower than other portions of the exterior body. Therefore, it can open more reliably and rapidly compared with embodiment described using FIGS. 1-3.

  The planar shape of the narrow portion 12n of the exterior body 12 is not limited to the trapezoid shown in FIGS. 4 and 5, but may be a semicircular shape or a triangular shape. In addition, the narrow width portion 12n of the outer body 12 is sufficient if the welding width at the position facing the notch portion 112n is narrower than the welding width of other portions. As described above, it is not limited to the one formed on the inner peripheral edge of the welded portion of the outer package, but may be formed on the outer peripheral edge of the welded portion of the outer package. Moreover, you may form the area | region where a welding width | variety is narrow by forming a hole between the inner periphery part and outer periphery part of the welding part of an exterior body. The planar shape of these narrow portions 12n can be easily formed by making the crimping die into a predetermined shape when the outer peripheral edge portions of the two laminate films are overlapped and thermocompression bonded. In order to form the portion 12n, it is not necessary to add a special process and the manufacturing cost is not increased.

  FIG. 6 and FIG. 7 show another example of the thin battery in which the exterior body 12 is devised. FIG. 6 is a plan view of the main part of the thin battery 30, and FIG. 7 is an enlarged perspective view of a region C in FIG. 6. 6 and 7, the same members as those in FIGS. 1 to 5 are denoted by the same reference numerals, and redundant description is omitted below.

  The thin battery 30 of the present embodiment shown in FIGS. 6 and 7 has a material 12a having a melting point lower than that of the other part in the part where the outer package 12 faces the notch part 112n of the separator 112 of the power generation element. doing. Specifically, for example, a material 12a having a melting point lower than that of the laminate seal material is interposed between the two laminate seals of the outer package 12 at the outer peripheral edge portion of the portion facing the notch portion 112n. By welding the outer peripheral edge portions of the two laminate sheets with the low-melting-point material 12a sandwiched therebetween, the low-melting-point material 12a is provided at the above-described portion.

  By having this low melting point material 12a, when the power generation element 11 generates heat, the separator 112 is thermally contracted and the positive electrode plate 111a and the negative electrode plate at the position of the notch 112n. When heat is generated by preferentially short-circuiting 111b or the like, the portion having the low melting point material 12a has a lower melting point than other portions of the outer package, and thus is more easily opened. Therefore, similarly to the embodiment described with reference to FIGS. 4 and 5, it can be reliably and quickly opened.

  The low-melting-point material 12a is a material that can be welded to the laminate film of the outer package 12, and has characteristics such as peel strength after welding required as a part of the outer package and anti-electrolytic solution properties, and an appropriate melting point. The material which has can be selected suitably.

  Each embodiment described above has shown an example in which the separator 112 of the power generation element 11 has the notch 112n. However, in the thin battery of the present invention, the outer peripheral edge of the separator 112 and the electrode plate 111a or 111b. The configuration for providing a portion whose distance from the outer peripheral edge of the other portion is shorter than other portions is not limited to the example in which the notch 112n is formed. As another example, there is an example in which a convex portion toward the outer peripheral edge of the separator is formed on a part of the outer peripheral edge of the electrode plate 111a or 111b.

  An embodiment in which a convex portion toward the outer peripheral edge of the separator is formed on a part of the outer peripheral edge of the positive or negative electrode plate 111a or 111b will be described with reference to FIGS. FIG. 8 is a plan view of the thin battery 40 of the present embodiment, and FIG. 9 is an enlarged perspective view of a region D of FIG. 8 and 9, the same members as those in FIGS. 1 to 7 are denoted by the same reference numerals, and redundant description is omitted below.

  As shown in FIG. 9, the thin battery 40 of the present embodiment shown in FIG. 8 and FIG. 9 is the outer peripheral edge of the positive electrode plate 111a and the negative electrode plate 111b constituting the electrode plate of the power generation element 11, as clearly shown in FIG. The outer peripheral end of the separator 112 extends toward the welded portion of the exterior body 12 rather than the portion. And the convex part 111c which goes to the outer-periphery edge part of the separator 112 is formed in a part of outer-periphery edge part of this positive electrode plate 111a or the negative electrode plate 111b. By forming the convex portion 111c, the distance between the tip end portion of the convex portion 111c of the electrode plate and the outer peripheral edge portion of the separator 112 is shorter than other portions. As a result, when the battery generates heat during an abnormality such as overcharge or dead short, the porous separator 112 thermally contracts. Then, in the convex part 111c part of the electrode plate, the distance between the outer peripheral edge of the separator 112 and the outer peripheral edge of the positive electrode plate 111a or the negative electrode plate 111b disappears, and the positive electrode plate 111a and the negative electrode plate 111b become In the convex part 111c of the electrode plate, the internal short circuit is preferentially performed earlier than other parts. Therefore, similarly to the embodiment shown in FIGS. 1 to 3, the welded portion of the exterior body at a portion facing the convex portion 111 c of the electrode plate serves as a safety valve. From this, it is possible to sufficiently secure the peel strength of the laminate sheet when the battery is normal and normal, and when the battery is abnormal such as overcharge or dead short, the exterior body near the convex portion 111c of the electrode plate Therefore, when the battery is abnormal, the exterior body can be reliably opened. In addition, the battery according to the present embodiment can realize the above-described effects only by simply forming the convex portion 111c cutout portion 112n at a part of the outer peripheral edge portion of the electrode plate. There is no need to provide. The notch 112n can be easily formed by punching or the like, for example, at the time of manufacturing the separator. Therefore, it is not necessary to add a special process to form the notch 112n, and the manufacturing cost is reduced. Does not bring rise.

  In the thin battery 40 of the present embodiment shown in FIGS. 8 and 9, the convex portion 111c of the electrode plate is provided at the central portion on the long side of the electrode plate having a substantially rectangular planar shape. The position of the part 111c is not limited to the illustrated example. In short, it is only necessary to provide a convex portion at any one of the outer peripheral edges of the electrode plate so that the positive electrode plate 111a and the negative electrode plate 111b can be preferentially short-circuited and generate heat in the event of an abnormality. And the position of the convex part is not limited. However, it is advantageous to provide the convex portion 111a on the long side as shown in the figure because there is no interference with the electrode terminal 13 or 14.

  In addition, the distance between the tip of the convex portion 111c and the outer peripheral edge of the separator 112, which is shortened by forming the convex portion 111c of the electrode plate, depends on the material of the separator 112, the area of the separator, and the like. Based on this, it can be appropriately determined as a value that can be preferentially short-circuited by the convex portion 111c in the event of an abnormality.

  Although the illustrated convex portion 111c has a trapezoidal planar shape, the planar shape of the convex portion 111c is not limited to a trapezoidal shape. For example, it may be semicircular or triangular.

  In the embodiment shown in FIGS. 8 and 9, as in the embodiment shown in FIGS. 4 and 5, the exterior body 12 is devised, that is, two laminated films are formed on a part of the exterior body 12. The narrow width portion 12n is formed so that the welding width is narrower than the welding width of other portions. This portion is a position facing the convex portion 111 c of the electrode plate of the power generation element 11.

  By forming the narrow width portion 12n, the separator 112 is thermally contracted at the time of an abnormality in which the power generation element 11 generates heat, and the positive electrode plate 111a and the negative electrode plate 111b are positioned at the convex portion 112c. When the internal short circuit preferentially generates heat, the narrow width portion 12n is easier to open because the welding width is narrower than other portions of the exterior body. Therefore, it can open more reliably and rapidly like embodiment described using FIG.4 and FIG.5.

  The thin battery according to the present invention has been described above with reference to the drawings. However, the thin battery according to the present invention is not limited to the embodiment shown in the drawings, and does not depart from the gist of the present invention. Many variations can be made. For example, in the embodiment shown in FIGS. 8 and 9, the outer body 12 is formed with a narrow width portion 12n, but the outer body 12 is shown in FIGS. 6 and 7 instead of the narrow width portion 12n. A configuration having the low melting point material 12a shown can also be employed.

It is a top view of the thin battery which concerns on embodiment of this invention. FIG. 2 is an enlarged perspective view of FIG. 1. It is a perspective view explaining the structure of an electric power generation element. It is a top view of the thin battery which concerns on embodiment of this invention. FIG. 5 is an enlarged perspective view of FIG. 4. It is a top view of the thin battery which concerns on embodiment of this invention. FIG. 7 is an enlarged perspective view of FIG. 6. It is a top view of the thin battery which concerns on embodiment of this invention. FIG. 9 is an enlarged perspective view of FIG. 8.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Thin battery 11 Electric power generation element 12 Exterior body 13 Electrode terminal 14 Electrode terminal 111a Positive electrode side electrode plate 111b Negative electrode side electrode plate 111c Convex part 112 Separator 112n Notch

Claims (6)

It has a positive electrode plate and a negative electrode plate as electrode plates, and has a planar separator larger than these electrode plates, and an outer peripheral edge portion of these positive electrode plate and negative electrode plate and an outer peripheral edge portion of the separator A power generating element in which a positive electrode plate and a negative electrode plate are laminated via a separator in a state where a distance is provided between them, and an outer package having a welded portion in which peripheral edges of two laminate sheets are welded to each other with a predetermined weld width In a thin battery that is sealed inside, the power generation element peels off the welded part at the time of abnormality that generates heat above a predetermined value, and opens the exterior body.
Provided in a part of the outer peripheral edge of at least one of the separator and electrode plate of this power generation element is a portion in which the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate is shorter than other parts. ,
When the abnormality occurs, the separator is thermally contracted by heat generation of the power generation element, and a portion that is shorter than the other part is configured to be short-circuited preferentially earlier than the other part. Thin battery. The thin battery has an outer periphery surrounded by four sides and is formed in a rectangular shape in plan view,
The positive electrode plate and the negative electrode plate are each connected to an electrode terminal, and the electrode terminal is led to the outside of the exterior body,
That the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate is shorter than the other part is provided at a position corresponding to a side other than the side from which the electrode terminal is derived. The thin battery according to claim 1.   By forming a notch portion toward the outer peripheral edge of the electrode plate in a part of the outer peripheral edge of the separator, the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate is increased. The thin battery according to claim 1, wherein the thin battery is shorter than other portions.   By forming a convex portion toward the outer peripheral edge of the separator on a part of the outer peripheral edge of the electrode plate, the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate is increased. The thin battery according to claim 1, wherein the thin battery is shorter than other portions.   A part of the outer peripheral edge of the laminate sheet of the exterior body, wherein the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate in the power generation element is shorter than other parts. The thin battery according to any one of claims 1 to 4, wherein a portion where the welding width is shorter than a welding width of another portion is provided in a portion at an opposing position.   A part of the outer peripheral edge of the laminate sheet of the exterior body, wherein the distance between the outer peripheral edge of the separator and the outer peripheral edge of the electrode plate in the power generation element is shorter than other parts. The thin battery according to any one of claims 1 to 4, wherein a portion having a melting temperature lower than that of the other portion is provided in a portion of the facing position.

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