JP2005310671A - Sealed battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sealed battery capable of effectively preventing deformation of a battery and reducing dimensional change in use for allowing highly precise layout designing. <P>SOLUTION: This sealed battery is provided with an armor material 4 formed of a metal laminated resin film having a drawn part 5 formed by drawing, a power generation element 1 housed in the drawn part 5 of the armor material 4, and external terminals 2 and 3 electrically connected to the power generation element 1. The circumference part of the armor material 4 is sealed by heat sealing, while the external terminals 2 and 3 are led to the outside via a part heat sealed to the metal laminated resin film serving as the armor material 4. In this sealed battery, a projection part 6 protruding to the sealed side of the external terminals 2 and 3 is formed on the side face of the drawn part 5 housing the power generation element 1. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sealed battery, and in particular, is a sealed battery in which a power generation element is housed in a drawn part of a drawn metal laminate resin film outer package, and then a peripheral part of the outer package is sealed. The present invention relates to a hermetic battery that can effectively suppress the dimensional change during use and can be highly accurately arranged.

  In recent years, there have been remarkable developments in technologies aimed at rapid performance enhancement, multifunctionalization, weight reduction, and miniaturization in portable electronic devices such as video cameras, headphone stereos, and portable terminals. Technical demands for higher energy and higher capacity of secondary batteries, which serve as drive power sources for time operation, are further increasing.

  In order to meet these technical demands, the development of non-aqueous electrolyte secondary batteries using materials that can occlude and release lithium, such as lithium metal, lithium alloys, or carbonaceous materials, is actively promoted. It became so. Among these non-aqueous electrolyte secondary batteries, from the technical point of view that reducing the volume occupied by elements other than the power generation element of the battery is advantageous for increasing the energy and size of the battery, it has been conventionally used as a battery exterior material. Instead of the metal cans made of iron or aluminum, a sealed battery using a metal laminate resin film that can be made thinner as an exterior material has attracted attention.

  The metal laminate resin film is formed by laminating and laminating a soft metal film such as an aluminum foil capable of preventing permeation of electrolyte solution, moisture and gas, and a plastic film such as nylon, polyethylene, and polypropylene. . When this metal laminate resin film is used as a battery exterior material, a structure in which the outer periphery of the exterior material is sealed by thermal fusion in a state where the power generation element is accommodated is generally employed.

  When adopting the above sealing structure, the form of the metal laminate resin film is roughly divided into two types, and as one conventional form, a laminated sheet metal laminate resin film is formed as a bag as it is, A configuration is adopted in which a power generation element (battery body) is housed inside (see, for example, Patent Document 1).

  Another form is a form in which the metal laminate resin film is subjected to a drawing process, and the power generation element is housed in the drawing part. In this case, in the latter form, since the drawn portion that matches the shape of the power generation element to be accommodated is formed, the ratio of the power generation element to the entire battery volume compared to the former bag-shaped exterior material There is an advantage that the battery capacity can be increased.

Furthermore, a structure in which a protruding portion that protrudes to the inside of the drawing portion is formed on the side wall of the deep drawing portion so as to approach the power generation element along the direction in which the electrode terminals extend (for example, Patent Documents). 2). According to the battery structure in which the projecting portion is formed, the projecting portion positions the power generation element in the drawing portion, so that the power generation element can be effectively prevented from moving in the drawing portion. As a result, since it is possible to prevent the power generating element from exerting stress on the electrode terminal, disconnection of the electrode terminal is avoided, and a battery with high reliability can be supplied.
Japanese Patent Laid-Open No. 11-40114 (page 1-3, FIG. 3) JP 2003-77426 A (page 1-3, FIG. 1)

  However, in the conventional battery in which the metal laminate resin film is formed in a bag shape as described in Patent Document 1 and the power generation element is housed therein, the battery is compared with a battery using a metal can as an exterior material. As a result, the battery is liable to be deformed. This is because the resin film is soft and flexible, and the strength of the exterior material itself is smaller than that of the metal can. For this reason, when gas is generated inside the battery due to overcharge operation, etc., the battery expands and deforms, making the battery thicker than the predetermined size, making layout design difficult, and applying stress to peripheral parts. There was a problem such as.

  In addition, with respect to deformation due to such an increase in battery internal pressure, a battery in which a metal laminate resin film is subjected to drawing may be more disadvantageous than a battery that is not subjected to drawing. In other words, in the case of a cell in which a metal laminate resin film is drawn, the drawn portion can be formed in almost the same shape as the outer shape of the power generation element, resulting in less wasted space in the battery. There is a problem that the battery is greatly deformed even by a slight amount of generated gas.

  On the other hand, as described in Patent Document 2, a protruding portion that protrudes inside the drawn portion is formed on the side wall of the deep drawn portion so as to approach the power generation element along the direction in which the electrode terminal extends. In the conventional battery, the overhang portions formed on both sides of the protruding portion are formed at positions that interfere with the heat fusion portion of the external terminal. For this reason, the width of the heat-sealed portion of the external terminal is reduced by an amount corresponding to the overhang height of the above-mentioned overhang portion, the hermetic sealing performance at the heat-welded portion is reduced, and the battery characteristics are reduced due to moisture mixing. There was also a problem that decreased.

  The present invention has been made in order to solve the problems occurring in the above-described conventional sealed battery, and in particular, the battery can be effectively prevented from being deformed, and the dimensional change during use is small and the layout design is highly accurate. An object of the present invention is to provide a sealed battery capable of achieving the above.

  In order to achieve the above object, a sealed battery according to the present invention includes an exterior material made of a metal-laminated resin film formed by drawing and forming a drawn portion, and a power generation housed in the drawn portion of the exterior material. The metal laminate resin comprising an element and an external terminal electrically connected to the power generation element, the peripheral portion of the exterior material being sealed by thermal fusion, and the external terminal being an exterior material In a sealed battery having a structure that is led to the outside via a portion that is heat-sealed to a film, a protrusion that protrudes toward the fusion side of the external terminal is formed on a side surface of the drawing portion that houses the power generation element. A portion is formed.

  That is, in the present invention, the convex portion is formed so as to protrude from the side surface of the drawn portion of the metal laminated resin film used as the exterior material. When gas is generated inside the battery, the generated gas is accommodated and absorbed by the convex portion, so that deformation of the battery can be effectively suppressed. That is, when gas is generated in the battery, it is possible to avoid swelling of the secondary battery by allowing the generated gas to escape and accumulate on the convex portions that do not affect the external dimensions of the battery. As a result, it is possible to supply a sealed battery having a stable quality with a large proportion of power generation elements in the battery and a high capacity and a small dimensional change during use.

  Further, in the sealed battery, it is preferable that a convex portion protruding from a side surface of the draw forming portion is formed at a position where it does not interfere with the heat fusion portion of the external terminal.

  If the formation position of the convex portion overlaps and interferes with the heat fusion portion of the external terminal, the width of the heat fusion portion of the external terminal is reduced by an amount corresponding to the overlap width, so that the sealing property is improved. The battery characteristics are likely to deteriorate. Therefore, as a position where the convex portion does not interfere with the heat fusion portion of the external terminal, for example, the heat fusion portion is formed by forming the convex portion at an intermediate position of the positive cathode external terminal or an outer position of each external terminal. The reduction in the width is avoided, the sealing performance is not lowered, and the deterioration of the battery characteristics can be reduced.

  Furthermore, in the sealed battery, when the peripheral portion of the metal laminate resin film exterior material containing the power generation element in the drawing molded portion is sealed by thermal fusion, the metal laminate resin film exterior material is formed. It is preferable that the inside of the drawn portion is sealed in a state where the pressure is reduced.

  As described above, by performing sealing work in a reduced pressure environment and sealing the inside of the drawn-formed part formed on the exterior material in a pre-reduced state, the useless space inside the battery can be reduced as much as possible. The effects of gas components and the like remaining in the battery from the battery manufacturing stage can be effectively avoided, and in particular, the effect of effectively preventing the deformation of the battery due to the increase in internal pressure accompanying the aging of the battery can be obtained.

  Further, in the sealed battery, a portion of the peripheral portion of the metal laminate resin film exterior material in which the power generation element is accommodated in the draw molding portion, the external terminal being thermally fused to the metal laminate resin film as the exterior material The length L (shown in FIG. 2) is preferably 3 mm or more.

  As described above, if the width of the portion where the external terminal is heat-sealed to the metal laminate resin film which is an exterior material is less than 3 mm, the sealing property of the heat-sealed portion becomes insufficient and moisture or the like is contained in the battery. There is a high risk that the battery characteristics will be impaired by mixing. For this reason, the length of the heat-sealed portion of the external terminal is preferably 3 mm or more. Furthermore, the length of the heat fusion part of the external terminal is more preferably in the range of 4 to 5 mm from the viewpoint of the volumetric efficiency of the battery.

  According to the sealed battery according to the present invention, since the convex portion is formed so as to protrude from the side surface of the drawn portion of the metal laminate resin film used as the exterior material, when gas is generated inside the battery, Since the generated gas is accommodated and absorbed in the convex portion, it is possible to effectively suppress the deformation of the battery. That is, when gas is generated in the battery, it is possible to avoid swelling of the secondary battery by allowing the generated gas to escape and accumulate on the convex portions that do not affect the external dimensions of the battery. As a result, it is possible to supply a sealed battery having a stable quality with a large proportion of power generation elements in the battery and a high capacity and a small dimensional change during use.

  Hereinafter, an example of an embodiment of a sealed battery according to the present invention will be described more specifically with reference to the accompanying drawings.

  FIG. 1 is an exploded perspective view showing a state where a power generation element 1 and an exterior material 4 constituting a sealed battery to which the present invention is applied are assembled. The power generation element 1 includes a negative electrode plate in which a negative electrode material is held on a negative electrode current collector that is a support, a positive electrode plate in which a positive electrode active material is held on a positive electrode current collector that is a support, and the negative electrode The separator is interposed between the plate and the positive electrode plate to hold the electrolytic solution and prevent a short circuit between the two electrodes. The negative electrode plate, the positive electrode plate, and the separator are all formed into a thin sheet shape or foil shape, and these laminated bodies are pressed around a predetermined winding axis and then pressed into a flat long cylindrical shape. Formed. The power generation element 1 is provided with a negative electrode lead 2 electrically connected to the negative electrode and a positive electrode lead 3 electrically connected to the positive electrode, both of which generate the power generation in a direction parallel to the winding axis. It extends from element 1.

  The power generating element 1 has a configuration in which a separator is disposed between a positive electrode plate and a negative electrode plate, and the separator holds the electrolytic solution. However, a solid electrolyte or a gel electrolyte is interposed between the positive electrode plate and the negative electrode plate. It is also possible to employ a power generation element formed by disposing.

  As the exterior material 4 that houses the power generating element 1, a metal laminate resin film that has been subjected to a drawing process to form a drawing part 5 and a convex part 6 is used. The metal laminate resin film is formed by bonding a thermoplastic metal film such as polyethylene, polypropylene, nylon, etc., for heat-sealing after housing the power generating element 1 to a soft metal thin film such as aluminum.

  The draw forming part 5 for storing the power generation element includes a molding part having a rectangular cross section slightly larger than that of the power generation element 1, and is formed on a side surface of the rectangular molding part and protrudes to the fusion side of the external terminal. Convex part 6 is provided. In addition, the dimension of the convex part 6 to form changes with size specifications of the electric power generation element 1 to be used. For example, when the width of the power generation element 1 is 30 to 40 mm, the width of the convex portion 6 is in the range of 8 to 12 mm, the protrusion amount is about 1 to 4 mm, and the height is the same as the height of the power generation element 1. A range of 4 to 5 mm is desirable from the viewpoint of the generated gas absorption capacity and the sealing property of the heat fusion part.

  As shown in FIG. 1, the method of housing the power generating element 1 in the metal laminate resin film exterior material 4 is to fold one side of the exterior material 4 formed with the rectangular drawn portion 5 and the convex portion 6. The power generating element 1 is housed so that the negative electrode lead 2 and the positive electrode lead 3 are pulled out from the side opposite to the valley-folded side, and the three peripheral edges other than the valley-folded side are heat-sealed. Thus, the final sealing method was adopted.

  In the above three-side fusion process, first, one side out of the side (top seal portion) from which the positive and negative electrode leads 2 and 3 are drawn and the two sides (side seal portion) parallel to the positive and negative electrode leads 2 and 3 are used. At the stage of heat sealing, the electrolyte is injected from the remaining one side (side seal part) side where heat sealing is not performed. Furthermore, when performing the thermal fusion of the unfused side (side seal part) after the electrolyte injection, the inside of the battery is brought into a decompressed state by adopting a method such as thermal fusion in a reduced pressure environment. The useless space inside the battery was reduced as much as possible.

  In a battery using a metal laminate resin film as an exterior material, the negative electrode terminal 2 and the positive electrode terminal 3 are pulled out to the outside via a heat-sealed portion (top seal portion) of the exterior material 4 as shown in FIG. It serves as an external terminal.

  Since the fused portion of the negative electrode terminal 2 and the positive electrode terminal 3 has a weak joint structure in which a metal and a resin are fused, sealing performance is improved as compared with a strong joint structure portion in which the resin of the exterior material is fused. Inferior. For this reason, it is desirable to seal the side from which the external terminal is drawn out before injecting the electrolyte. Further, in order to improve the sealing performance of the portion where the negative electrode lead 2 and the positive electrode lead 3 are heat-sealed to the outer packaging material 4, the negative electrode lead 2 and the positive electrode lead 3 are packaged via another resin film that is easily bonded to a metal. It is preferable to fuse with the material 4.

  Furthermore, in the sealed battery according to the present embodiment, the greater the distance (heat fusion width) at which the exterior material 4 and the external terminal are fused, the easier it is to obtain excellent sealing performance. Therefore, it is desirable to form the convex portion 6 to be formed at a position where it does not overlap with the fused portion of the external terminal, that is, at a position intermediate between the positive cathode external terminals or an outer position of each external terminal.

  Moreover, it is desirable to seal in the state which pressure-reduced the inside of a battery as a means to make the magnitude | size of a battery small as much as possible in this sealing operation.

[Example]
Next, embodiments to which the present invention is applied will be described more specifically with reference to the following examples and comparative examples.

[Example 1]
As shown in FIG. 1, a power generation element 1 having dimensions such that the length in the direction parallel to the winding axis is 34 mm, the width is 29 mm, and the thickness is 6 mm was prepared. The widths of the negative electrode lead 2 and the positive electrode lead 3 serving as external terminals were each 2 mm. The negative electrode lead 2 and the positive electrode lead 3 extend from the power generation element 1 in a direction parallel to the winding axis, and the distance between the positive and negative electrode leads is 6 mm from the center of the width of the power generation element 1. Was connected to be 12 mm.

  As a metal laminate resin film used as the exterior material 4, an aluminum laminate film composed of three layers of a nylon layer having a thickness of 25 μm, a soft aluminum layer having a thickness of 40 μm, and a polypropylene layer having a thickness of 30 μm was prepared. Next, the exterior material 4 is subjected to a drawing process so that the nylon layer is on the outside using a drawing machine comprising a punch and a die, and a rectangular drawing part 5 as shown in FIG. And the exterior material 4 which formed the convex part 6 was manufactured.

  The drawing portion 5 includes a rectangular portion in which the power generation element 1 is accommodated and a convex portion 6 protruding from the side surface of the rectangular portion. The size of the rectangular portion is 35 mm in length and width. Was 30 mm and the depth was 6 mm. As shown in FIG. 2, the convex portion 6 is located at the center of the side surface on the side where the external terminals 2 and 3 are fused and drawn to the outside, and the entire portion having a molding depth of 6 mm is the external terminals 2 and 3. It was formed at a position where it does not overlap with the heat-sealed part, and the width was 9 mm and the protruding amount was 3 mm.

  The exterior material 4 was sealed by folding the side facing the side surface on which the convex portion 6 was formed to accommodate the power generating element 1 and heat-sealing three sides other than the side folded. This sealing operation was performed by sandwiching and heat-sealing the portion of the outer packaging material 4 that was overlapped by being bent by a heater or a metal plate incorporating the heater. In the above three-side fusion process, first, one side of the side (top seal portion) from which the positive and negative electrode leads 2 and 3 are drawn and the two sides (side seal portion) parallel to the positive and negative electrode leads 2 and 3 is thermally fused. At the stage of wearing, the electrolytic solution was injected from the remaining one side (side seal portion) side where heat fusion was not performed.

  The width of the heat fusion is such that the exterior material 4 is cut so that the length of the folded exterior material 4 is 41 mm on the side surface where the convex portion 6 for heat-sealing the external terminals 2 and 3 is located. Prepare a heater with a shape such that the fusion width of the portion where the convex portion 6 exists is 2 mm, while the fusion length of the portion where the external terminals 2 and 3 are fused is 5 mm, and rectangular drawing The immediate outside of the part 5 and the convex part 6 was heat-sealed. In addition, the two sides were heat-sealed so that the fusion width was 2 mm, but the inside of the fusion part (one side of the side seal part) that was to be finally sealed after the electrolyte injection was reduced in pressure. Fused in the state. As a result, a sealed battery according to Example 1 having a shape and structure as shown in FIG. 2 was finally prepared.

[Example 2]
In addition to the convex portion 6 formed at the center of the side surface of the drawn portion 5 in the first embodiment, as shown in FIG. 3, at the two sides on the side surface side of the same drawn portion 5 and outside the outer terminal fusion portion. The power generation element 1 having the same specifications as in Example 1 is used except that the protrusions 6a and 6b each having a width of 6 mm and a protrusion amount of 3 mm are formed, respectively, A sealed battery according to Example 2 having a shape and a structure as shown in FIG. 3 was finally prepared by performing the injection of the electrolytic solution and the heat fusion treatment.

[Comparative Example 1]
Except that no convex portion is formed on the side surface and the fusion width on the side surface from which the external terminals 2 and 3 are pulled out is all 5 mm, the power generation element 1 having the same specifications as in Example 1 is used, A sealed battery according to Comparative Example 1 having a conventional shape and structure as shown in FIG. 4 was finally prepared by carrying out a molding process, injection of an electrolytic solution, and heat fusion treatment.

[Comparative Example 2]
Instead of forming a locally projecting protrusion on the side surface of the drawn portion 5, a space that extends in the pull-out direction of the external terminals 2, 3 of the power generation element 1 is formed on the entire end surface of the power generation element 1. The dimensions of the drawn portion 5 are 38 mm in length, the width is 30 mm, and the fusion width on the side surface from which the external terminals are drawn out is all 2 mm including the fusion portions of the external terminals 2 and 3. A sealed battery according to Comparative Example 2 having a conventional structure was prepared by using a power generation element 1 having the same specifications as in Example 1 and performing drawing processing of an exterior material, injection of an electrolytic solution, and heat fusion treatment. .

  The thickness of each battery sample before and after the endurance test in which the samples of 100 sealed batteries according to each Example and Comparative Example prepared as described above were left in a high temperature environment of 90 ° C. for 24 hours. Were measured with a micrometer, and the average values of changes in battery thickness before and after the durability test were compared.

Moreover, the sealing part of each battery was inspected by visual observation after the high-temperature endurance test, and the number of samples that generated leakage (leakage) of the electrolyte was counted. These measurement count results are shown in Table 1 below.

  As is clear from the results shown in Table 1 above, the first and second embodiments in which the convex portions 6, 6 a, 6 b are formed so as to protrude from the side surface of the drawn portion 5 of the metal laminate resin film used as the exterior material 4. According to the sealed battery according to the present invention, even when gas is generated inside the battery in a high temperature environment, the generated gas is accommodated and absorbed by the convex portions 6, 6 a, and 6 b, so that the amount of change in battery thickness is small. It has been found that small battery deformation can be effectively suppressed. In other words, even when gas is generated in the battery, it is possible to avoid the swelling of the secondary battery by letting the generated gas escape and accumulate in the convex portions 6, 6 a, 6 b that do not affect the external dimensions of the battery. did it. As a result, it is possible to supply a sealed battery having a stable quality with a large proportion of power generation elements in the battery and a high capacity, and a small dimensional change during use.

  On the other hand, in the battery sample according to Comparative Example 1 in which no convex portion is formed, the battery thickness after being left in a high temperature environment has increased by an average value of 0.5 mm, depending on the use conditions. It was found that the amount of deformation increased. In contrast, all the samples according to Examples 1 and 2 in which the convex portions 6, 6a and 6b are locally formed have a smaller thickness increase than the sample of Comparative Example 1, and the shape stability is excellent. Yes. From this, it has been found that an increase in battery thickness due to gas generation inside the battery can be effectively suppressed by forming convex portions.

  On the other hand, in the battery sample according to the comparative example 2 in which the length in the longitudinal direction of the drawing portion 5 is 3 mm longer than the length in the longitudinal direction of the power generating element 1, the escape space for the generated gas in the drawing portion 5 is sufficiently large. Therefore, the amount of increase in battery thickness before and after the durability test is as small as that in Example 1. However, since the fusion length of the external terminal is as short as 2 mm, the ratio of the batteries in which the sealing property of the terminal fusion part deteriorates in a high temperature environment and the electrolyte solution leaks rapidly. Further, even after the endurance test, a further increasing tendency of the thickness of the battery was observed because of the intrusion of moisture from the outside.

  Furthermore, in the sealed battery according to Example 1 shown in FIG. 2, the length L of the portion where the external terminals 2 and 3 are thermally fused to the metal laminate resin film which is the exterior material 4 varies from 1 to 5 mm. When various types of sealed batteries were prepared and the percentage of batteries that had leaked after the same high-temperature durability test as described above was counted, the length L of the heat-sealed portion was 3 mm or more. It was confirmed that the number of leaking batteries can be made almost zero.

  From the above durability test results, the battery samples of Examples 1 and 2, which are embodiments of the present invention, are smaller in the amount of change in battery thickness when generating internal gas than the battery sample of the comparative example, and sealed. It was proved that a battery with high reliability of the part could be obtained.

The disassembled perspective view which shows the state which assembled the electric power generation element and exterior material which comprise the sealed battery to which this invention was applied. The perspective view which shows roughly the external structure of the sealed battery to which this invention was applied. The perspective view which shows schematically the external structure of the sealed battery which concerns on the other Example of the sealed battery to which this invention was applied. The perspective view which shows roughly the external structure of the sealed battery of a prior art example.

Explanation of symbols

1 Power generation element 2 Negative electrode lead (negative electrode terminal)
3 Positive lead (positive terminal)
4 Exterior material (metal laminate resin film)
5 Drawing forming parts 6, 6a, 6b Convex part L Length of heat-sealed part of external terminal

Claims (4)

An exterior material made of a metal-laminated resin film formed by drawing to form a drawn part, a power generation element housed in the drawing part of the exterior material, and an external terminal electrically connected to the power generation element And the outer periphery of the exterior material is sealed by thermal fusion, and the external terminal is led out to the outside via a portion that is thermally fused to the metal laminate resin film as the exterior material. In the sealed battery having the above structure, a projecting portion that protrudes toward the fusion side of the external terminal is formed on a side surface of the drawn portion that houses the power generating element. The sealed battery according to claim 1, wherein a convex portion protruding from a side surface of the draw-molded portion is formed at a position where it does not interfere with the heat fusion portion of the external terminal. When the peripheral part of the metal laminate resin film exterior material containing the power generation element in the draw molding part is sealed by thermal fusion, the inside of the draw part formed in the metal laminate resin film exterior material is decompressed The sealed battery according to claim 1, wherein the sealed battery is sealed with. Of the peripheral portion of the metal laminate resin film exterior material in which the power generation element is housed in the drawing portion, the length of the portion where the external terminal is heat-sealed to the metal laminate resin film as the exterior material is 3 mm or more. The sealed battery according to claim 1.

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