JP2006032225A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of preventing drop in battery characteristics caused by widening the distance between electrodes of a power generating element 1 by bulging only bulging parts 21b, 22b of an aluminum laminate films 21, 22 when the internal pressure of the battery is increased. <P>SOLUTION: In the battery using the aluminum laminate films 21, 22 formed by laminating a resin base film layer and a sealant layer on each surface of an aluminum foil, recessed parts 21a, 22a for inserting the power generating element 1 are formed in the aluminum laminate films 21, 22, and the bulged parts 21b, 22b in which the thickness is decreased in the whole part are formed in the four corners of the bottom surface of the recessed parts 21a, 22a. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery using an aluminum laminate film or the like as a battery case.

  FIG. 4 shows a configuration example of a conventional nonaqueous electrolyte secondary battery using an aluminum laminate film as a battery case. In this non-aqueous electrolyte secondary battery, a battery case 2 that houses a power generation element 1 is composed of two rectangular aluminum laminate films 21 and 22. The power generation element 1 has a long cylindrical shape in which a belt-like positive electrode and a negative electrode are wound through a separator, and a positive electrode lead terminal 3 and a negative electrode lead terminal 4 are projected from a front end surface.

  The two aluminum laminate films 21 and 22 constituting the battery case 2 are formed by laminating a base film layer made of nylon resin or the like on one surface of a metal layer made of aluminum foil and a sealant layer made of polypropylene or the like on the other surface. Is a rectangular flexible laminate film having a three-layer structure. In addition, the aluminum laminate films 21 and 22 have the surface on the sealant layer side drawn in advance in the center so that the upper half and the lower half of the long cylindrical power generation element 1 can be fitted. Recessed recesses 21a and 22a are formed. The two aluminum laminate films 21 and 22 are overlapped with the sealant layers facing each other, the power generation element 1 is fitted into the space formed by the recesses 21a and 22a, and the peripheral portion is filled with the electrolytic solution. By heat-welding, the battery case 2 is sealed inside. The lead terminals 3 and 4 projecting from the front end face of the power generation element 1 are sealed through the overlap between the peripheral edges of the two aluminum laminate films 21 and 22 at the front end, and project outside. ing.

  As shown in FIG. 5, the nonaqueous electrolyte secondary battery has flat bottom surfaces of the recesses 21a and 22a of the aluminum laminate films 21 and 22 (however, the upper recess 21a is stacked upside down, This bottom surface appears as a surface on the ceiling side in the figure.) Presses the flat side surface of the long cylindrical power generation element 1 from above and below, so that the distance between the positive electrode and the negative electrode of this power generation element 1 is constant. To be kept.

  However, when this non-aqueous electrolyte secondary battery is used, for example, in a high-temperature atmosphere, the electrolytic solution is decomposed and gas is generated. This gas increases the pressure in the battery case 2. Then, when the battery internal pressure increases in this way, the bottom surfaces of the recesses 21a and 22a of the aluminum laminate films 21 and 22 are pressed from the inside and swell outward as shown in FIG. The side surface is also released from the pressure applied by the bottom surface and bulges outward to increase the distance between the positive electrode and the negative electrode. For this reason, in the nonaqueous electrolyte secondary battery using the conventional aluminum laminate films 21 and 22 for the battery case 2, when the battery internal pressure rises, the bottom surfaces of the recesses 21a and 22a of the aluminum laminate films 21 and 22 bulge outward. For this reason, there has been a problem that the inter-electrode distance of the power generation element 1 is increased and the battery characteristics are deteriorated.

  Some batteries using a metal plate or the like for the battery case include a thin part formed on a part of the metal plate or the like of the battery case (see, for example, Patent Documents 1 and 2). However, these thin portions of Patent Documents 1 and 2 function as a safety valve by opening at break when the battery internal pressure rises, and thus are formed in a groove shape so as to be easily broken. Moreover, although the thin part of patent document 1 blocks | closes an opening hole with metal foil, or when thinning the thickness of metal plates etc. itself is shown (0042 paragraph), when closing an opening hole with metal foil, it is shown. However, since machining such as cold welding is required, and cutting or the like is necessary to reduce the thickness of the metal plate or the like, it takes time and effort for these processes. In addition, even if the thickness of the thin part such as the metal plate is reduced, the material itself hardly expands, so that it hardly swells when the battery internal pressure rises, and when it exceeds a predetermined pressure, it immediately breaks. .

Also, some batteries using a laminate film in which a resin layer is laminated on the front and back surfaces of a metal layer as a battery case include a thin part formed on a part of the laminate film of the battery case (for example, Patent Documents 3 to 3). 4). However, since the thin-walled portion of Patent Document 3 functions as a safety valve by opening at break when the internal pressure of the battery rises, only the thickness of the resin layer having the highest mechanical strength (usually the outermost base film layer) is limited. The metal layer, which is thin and does not easily stretch, is easily broken when the battery internal pressure rises. Furthermore, the thin part of patent document 4 is provided in order to improve the shape stability of the recessed part of the laminate film formed by drawing, For this reason, only the thickness of the metal layer is made thin. .
JP 2001-266812 A JP 2002-237283 A JP 2000-353501 A JP 2002-216711 A

  The present invention seeks to solve the problem that by forming an inflated part in a part of the laminate film, the laminate film is entirely inflated to increase the distance between the electrodes of the power generating element and to deteriorate the battery characteristics. It is.

  The invention of claim 1 is a battery in which a multilayer laminate film in which a resin layer is laminated on the front and back surfaces of a metal layer is used for a battery case. The formed inflatable part is formed.

  In the invention of claim 2, the laminate film is formed with recesses for fitting the power generating elements, and at the four corners of the bottom surface of the recesses, inflated portions each having a thickness reduced in all layers are formed. It is characterized by that.

  According to the first aspect of the present invention, since the thin expanded portion is formed in a part of the laminate film, when the battery internal pressure rises, the expanded portion swells and relaxes the pressure before the other portions. be able to. For this reason, the pressure on the side surface of the power generation element is not weakened by the majority of the laminate film swelled, and the battery characteristics can be prevented from being deteriorated due to the increase in the distance between the electrodes of the power generation element. Become. Moreover, since the thickness of each layer of the inflated portion is not limited to a specific layer, but the entire thickness is reduced, the properties of the laminate film, such as tensile strength, difficulty in stretching, and elasticity, are gradually weakened. The bulge is surely expanded at a lower pressure than the portion having a normal thickness.

  According to the invention of claim 2, since the expanded portions are formed at the four corners of the bottom surface of the concave portion of the laminate film, even when these expanded portions are expanded due to an increase in the battery internal pressure, the central portion of the bottom surface of the concave portion is formed. The side surface of the power generation element can be continuously pressed, and the battery characteristics can be reliably prevented from deteriorating. In addition, the four corners of the bottom surface of the concave portion are portions where the peripheral laminate film is greatly curved in the three-dimensional direction to increase the strength, so even if the inflated portion swells here, the entire bottom surface swells. There is no fear.

  Hereinafter, the best embodiment of the present invention will be described with reference to FIGS. 1 to 3, the same reference numerals are given to the constituent members having the same functions as those of the conventional example shown in FIGS. 4 to 6.

  In the present embodiment, a non-aqueous electrolyte secondary battery using two aluminum laminate films 21 and 22 for the battery case 2 will be described as in the conventional example. Similar to the conventional example shown in FIG. 4, the aluminum laminate films 21 and 22 are rectangular flexible films having a three-layer structure in which a base film layer is laminated on one surface of a metal layer and a sealant layer is laminated on the other surface. It is a laminate film, and concave portions 21a and 22a in which the surface on the sealant layer side is recessed by drawing processing are formed in most of the center in advance. Here, the metal layer is made of an aluminum foil, and is an intermediate layer provided in order to secure the gas barrier property of the battery case 2 and reliably prevent leakage of the non-aqueous electrolyte. The base film layer is a resin layer such as nylon, and is an outer layer provided to increase the strength of the battery case 2. Furthermore, the sealant layer is made of a thermoplastic resin such as polypropylene, and is an inner layer provided for thermally welding the peripheral portions of the aluminum laminate films 21 and 22.

  When the aluminum laminate films 21 and 22 are drawn to form the concave portions 21a and 22a, the expanded portions 21b and 22b are formed at the four corners of the bottom surfaces of the concave portions 21a and 22a, respectively. In the nonaqueous electrolyte secondary battery shown in FIG. 1, the four expanded portions 21 b formed on the upper aluminum laminate film 21 are represented by dot hatching. As shown in FIG. 2, these inflatable portions 21 b are portions where the thickness of the aluminum laminate film 21 is thinner in all layers than in other portions. And the expansion part 22b is formed in the same four places also in the lower aluminum laminate film 22 which is not illustrated. Such inflatable portions 21b and 22b are provided with a slight convex portion on the surface of the corresponding portion in one or both of the drawing molds, so that the aluminum laminate films 21 and 22 of the convex portion can be removed from both sides. It can be formed by pressing more strongly than this part to reduce the thickness. In addition, the thickness of the aluminum laminate films 21 and 22 of the expanding portions 21b and 22b is thin in all layers. That is, only one or two layers of the metal layer, the base film layer, and the sealant layer are the other layers. Rather than being thinner than the part of the layer, it means that all three layers are a little thinner. However, these three layers need not all be thinned at an equal rate, and the degree to which each layer is thinned by the pressure of pressing may be different.

  The aluminum laminate films 21 and 22 are stacked with the sealant layers facing each other in the same manner as in the conventional example, and after the power generation element 1 is fitted into the space formed by the recesses 21a and 22a, and the electrolyte is filled A battery case 2 of a non-aqueous electrolyte secondary battery is obtained by thermally welding the peripheral edge over the entire circumference.

  According to the non-aqueous electrolyte secondary battery having the above configuration, the expanded portion 21b whose thickness is reduced in all layers is formed on a part of the bottom surface of the recesses 21a and 22a of the aluminum laminate films 21 and 22 constituting the battery case 2. 22b is formed, for example, when the internal pressure of the battery rises due to use in a high-temperature atmosphere, the expansion portions 21b and 22b swell before the other portions of the bottom surface to relieve the pressure. . For this reason, since the side surface of the power generation element 1 is continuously subjected to pressure at the bottom surfaces of the recesses 21a and 22a other than the expanded portions 21b and 22b, the battery characteristics are deteriorated by increasing the distance between the positive electrode and the negative electrode. There is nothing wrong. In addition, since the inflating portions 21b and 22b are formed at the four corners of the bottom surfaces of the recesses 21a and 22a, the power generating element 1 can reliably keep pressing the center portion of the side surface that is most likely to bulge at the center portion of the bottom surface. It is possible to reliably prevent the distance between the poles from spreading. In addition, the four corners of the bottom surfaces of the recesses 21a and 22a are high-strength portions in which the aluminum laminate films 21 and 22 on the peripheral side are greatly curved in the three-dimensional direction, so that the expanding portions 21b and 22b are swollen by the internal pressure of the battery. However, there is no risk that the entire bottom surface swells due to bending around the periphery. Further, the expanded portions 21b and 22b are not limited to a specific layer of the three-layered aluminum laminate films 21 and 22, but each layer is thinned by pressing, so that the tensile strength, difficulty of stretching, elasticity, etc. The ratio of these characteristics remains almost the same, and these characteristics are weakened as a whole. Therefore, even if the battery internal pressure rises to some extent, the expansion portions 21b and 22b do not swell sufficiently or break before they fully swell, and the pressure is lower than the internal pressure at which other portions of the bottom surface swell. Will surely swell.

  In the above embodiment, the expansion portions 21b and 22b are formed when the drawing processing for forming the recesses 21a and 22a in the aluminum laminate films 21 and 22 is performed. However, the expansion portions 21b and 22b The formation method is not particularly limited. However, these expanded portions 21b and 22b are formed by reducing the thickness of the aluminum laminate films 21 and 22 in all layers. Can not.

  Moreover, in the said embodiment, although the case where the expansion parts 21b and 22b were formed in the four corners of the bottom face of the recessed parts 21a and 22a in the aluminum laminate films 21 and 22, this formation location and formation number are not limited. That is, if the expansion parts 21b and 22b are parts other than the peripheral part directly overlapping for heat welding in the aluminum laminate films 21 and 22 (parts covering the power generation element 1), the increase in battery internal pressure can be alleviated. Therefore, it may be formed anywhere, for example, it can be formed in a portion other than the four corners of the bottom surface of the recesses 21a and 22a or a portion other than the bottom surface. However, in order to reliably press the central portion of the side surface of the power generating element 1 that is most likely to swell, it is preferably formed on the peripheral edge of the bottom surface of the recesses 21a and 22a, and is formed over the entire periphery of the peripheral edge. Then, since there is a possibility that the central portion of the bottom surface may be lifted together when the battery internal pressure rises, it is preferable to form it by dividing it into several places with sufficient intervals. Furthermore, although the case where the expansion parts 21b and 22b were formed in the bottom face of the recessed parts 21a and 22a of both the aluminum laminate films 21 and 22 was shown in the said embodiment, these expansion parts 21b and 22b raise the battery internal pressure. Since it is for relaxing, it can be formed only on one of the aluminum laminate films 21 or 22.

  Moreover, in the said embodiment, although the case where the bottom face of the recessed parts 21a and 22a of the aluminum laminate films 21 and 22 was a flat surface was shown, these recessed parts 21a and 22a are compressed along the shape of the side surface of the electric power generation element 1. Therefore, the bottom surface and the entire recesses 21a and 22a may be curved surfaces. For example, when the power generation element 1 has an elliptical cylindrical shape, the shape of each of the recesses 21a and 22a can be a shape obtained by dividing the elliptical cylindrical shape into two, and the power generation element 1 has a cylindrical shape. In the case of a thing, these recesses 21a, 22a can also be semi-cylindrical. Furthermore, in the said embodiment, although the case where the recessed part 21a, 22a was formed in both of the two aluminum laminate films 21 and 22 was shown, it can also form only in any one aluminum laminate film 21 or 22, On the other hand, a flat sheet can be used as it is.

  Further, in the above embodiment, the case where the battery case 2 is configured by superimposing the two aluminum laminate films 21 and 22 is shown. However, the configuration of such an aluminum laminate film is arbitrary, for example, one aluminum sheet. The battery case 2 can also be configured by folding the laminate film in half. Furthermore, when the aluminum laminate film is stacked and sealed, other fixing means such as adhesion can be used instead of heat welding.

  Moreover, although the case where the aluminum laminated film was used was shown in the said embodiment, a metal layer is not restricted to aluminum foil, If a laminated film can acquire sufficient barrier property, other metal foil can also be used. Furthermore, this metal layer can be formed of a metal vapor deposition film formed on the inner surface side of the base film layer, for example, instead of the metal foil. Furthermore, the resin material of the base film layer and the sealant layer laminated on the front and back surfaces of the metal layer is also arbitrary, and if the thermal welding is not performed, the thermoplastic resin of the sealant layer is a layer of other resin materials. You can also. Furthermore, since the laminate film is only required to have a resin layer laminated on the front and back surfaces of the metal layer, the metal layer and the resin layer may each further have a multilayer structure.

  Moreover, in the said embodiment, although the case where the lead terminals 3 and 4 were pulled out from the front end surface of the electric power generation element 1 was shown, the lead-out means of these lead terminals 3 and 4 is also arbitrary. Furthermore, although the non-aqueous electrolyte secondary battery has been described in the above embodiment, the type of the battery is arbitrary, and the present invention can be similarly applied to other secondary batteries and primary batteries.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan view of a nonaqueous electrolyte secondary battery using an aluminum laminate film as a battery case according to an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial cross-sectional enlarged perspective view illustrating an embodiment of the present invention and illustrating a configuration of an expanded portion of an aluminum laminate film. 1 is a cross-sectional front view of a nonaqueous electrolyte secondary battery in which an embodiment of the present invention is shown and the internal pressure of the battery is increased. FIG. 9 is a perspective view showing a conventional example, and is an assembled perspective view showing a structure of a nonaqueous electrolyte secondary battery using an aluminum laminate film as a battery case. It is a cross-sectional front view of the nonaqueous electrolyte secondary battery which shows a prior art example and the battery internal pressure rose. It is a cross-sectional front view of the nonaqueous electrolyte secondary battery which shows a prior art example and the battery internal pressure rose.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power generation element 2 Battery case 21 Aluminum laminated film 21a Recessed part 21b Expanding part 22 Aluminum laminated film 22a Recessed part 22b Expanding part

Claims (2)

In a battery using a multilayer laminate film in which a resin layer is laminated on the front and back surfaces of a metal layer for a battery case,
A battery characterized in that an expanded portion having a reduced thickness in all layers is formed in a partial region of the laminate film.   The laminate film is formed with recesses for fitting power generation elements, and at the four corners of the bottom surface of the recesses, expanded portions each having a thickness reduced in all layers are formed. Item 6. The battery according to Item 1.

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