JP2005141955A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery surely achieving sealing by heat bonding in a case where a lead terminal is very thick and preventing the contact of the lead terminal with a barrier metal layer. <P>SOLUTION: A power generating element 3 is housed between aluminum laminate sheets 1, 2 in which sealant layers 13, 23 made of thermoplastic resin are formed on the insides of the barrier metal layers 12, 22, lead terminals 4, 5 are taken out of the overlapped part of the aluminum laminated sheets 1, 2, and the battery is sealed by heat bonding the sealant layers 13, 23 of the overlapped part. The thickness T<SB>t</SB>of the lead terminals 4, 5 is in a range of 0.15 mm<T<SB>t</SB><0.5 mm, and the aluminum laminate sheets 1, 2 in which the thickness T<SB>s</SB>of the sealant layers 13, 23 satisfies the relation of 0.8T<SB>t</SB><2T<SB>s</SB><1.0T<SB>t</SB>are used. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a battery in which a power generation element is housed in an exterior body such as an aluminum laminate sheet.

  In portable electronic devices and the like, batteries that are thin and light have been conventionally used by using an aluminum laminate sheet for an exterior body that houses a power generation element. FIG. 4 shows a conventional configuration example of a lead-out portion of the positive electrode lead terminal 4 or the negative electrode lead terminal 5 in the nonaqueous electrolyte secondary battery in which the power generation element 3 is accommodated between two aluminum laminate sheets 1 and 2. The aluminum laminate sheets 1 and 2 are flexible films in which base film layers 11 and 21 made of nylon resin, barrier metal layers 12 and 22 made of aluminum foil, and sealant layers 13 and 23 made of thermoplastic resin are laminated in a laminate. It is a sheet. The positive electrode lead terminal 4 is made of strip-shaped aluminum foil, the base is ultrasonically welded to the positive electrode aluminum foil protruding on one end face of the power generation element 3, and the negative electrode lead terminal 5 is made of strip-shaped copper foil, The base is ultrasonically welded to the negative copper foil protruding on the other end face of the power generation element 3. These lead terminals 4, 5 protrude to the outside through the gaps between the peripheral edges of the upper and lower aluminum laminate sheets 1, 2. In addition, the peripheral portions of the upper and lower aluminum laminate sheets 1 and 2 are pressed and heated from above and below with the lead terminals 4 and 5 sandwiched therebetween, so that the thermoplastic resins of the sealant layers 13 and 23 are melted and thermally welded. Therefore, the heat welding parts 1b and 2b are formed and the inside is sealed.

Here, the sealant layers 13 and 23 of the aluminum laminate sheet 2 has a thickness _{T s} is a layer of thermoplastic resin of about 0.025Mm～0.03Mm. In addition, since the conventional non-aqueous electrolyte secondary batteries using such aluminum laminate sheets 1 and 2 as the exterior body have a relatively small capacity, the current flowing through the lead terminals 4 and 5 is also relatively small. , and the thickness _{T t} of aluminum or copper foil of lead terminals 4 and 5, it was used of about 0.07Mm～0.1Mm. When such thin lead terminals 4 and 5 are used, the heat-welded portions 1b and 2b of the aluminum laminate sheets 1 and 2 are also slightly spread between the sheets at the portion sandwiching these lead terminals 4 and 5. Therefore, the sealant layers 13 and 23 having a thickness T _s of about 0.025 mm to 0.03 mm can be sufficiently surely sealed.

However, recently, with the increase in capacity of nonaqueous electrolyte secondary batteries, there has been a demand to make the thickness _Tt of the aluminum foil and copper foil used for the lead terminals 4 and 5 extremely thicker than before. It is getting stronger. Specifically, there is a demand to make the thickness T _t of the lead terminals 4 and 5 thicker than 0.15 mm and thinner than 0.5 mm. Then, use this when very thick lead terminals 4 and 5, conventional aluminum laminate sheet 2 having a thin sealant layer 13 and 23 of thickness _{T s} of about the same 0.025mm~0.03mm In this case, the heat-welded portions 1b and 2b sandwiching the lead terminals 4 and 5 become insufficiently sealed, or the lead terminals 4 and 5 come into contact with the barrier metal layers 12 and 22 to cause a short circuit. There was a problem that there was a case.

That is, when the thickness T _t of the lead terminals 4 and 5 becomes 0.15 mm to 0.5 mm, which is much thicker than before, the thickness T _s of the sealant layers 13 and 23 remains 0.025 mm to 0.03 mm as before. If it is, these total thickness 2T _s of the combined thickness of each _{T s} of the upper and lower sealant layers 13 and 23, is 10% to 40% of the thickness _{T t} of the lead terminals 4 and 5, Compared to the thickness T _t of the lead terminals 4 and 5, the thickness T _s of the sealant layers 13 and 23 is extremely thin. In addition, in the heat-welded portions 1b and 2b of the aluminum laminate sheets 1 and 2, the space between the sheets is greatly expanded vertically between the extremely thick lead terminals 4 and 5, so the aluminum laminate is formed on the side surfaces of these lead terminals 4 and 5. Sheets 1 and 2 are not sufficiently along. For this reason, even if the sealant layers 13 and 23 are melted by thermal welding, the gaps between the side surfaces of the lead terminals 4 and 5 cannot be sufficiently filled, and a slight gap may remain. Further, if the thickness _Tt of the lead terminals 4 and 5 is thick, the heat applied to the aluminum laminate sheets 1 and 2 at the time of heat welding passes through the aluminum foil or copper foil of the lead terminals 4 and 5 having good thermal conductivity. Since a large amount of heat is dissipated, the amount of heat is insufficient near the lead terminals 4 and 5, and the sealant layers 13 and 23 are not sufficiently melted and the lead terminals 4 and 5 are easily separated. Further, if the thickness _Tt of the lead terminals 4 and 5 is thick, the upper and lower aluminum laminate sheets 1 and 2 are greatly curved at the side end portions of the lead terminals 4 and 5, so that the resin of the thin sealant layers 13 and 23 is obtained. As a result, the barrier metal layers 12 and 22 are exposed, and the side ends of the lead terminals 4 and 5 may be in direct contact with each other. In particular, if a large amount of heat is applied during heat welding in order to prevent the above sealing from becoming insufficient, the resin of the sealant layers 13 and 23 tends to flow out, and the lead terminals 4 and 5 and the barrier metal Contact with the layers 12 and 22 is likely to occur.

Note that proposals thicker than the thickness T _t of the upper and lower aluminum laminate thickness combined sealant layers 13, 23 of the sheet 1, 2 2T _s lead terminals 4 and 5 have been conventionally made (e.g., JP 1 and 2). For example, in the invention described in Patent Document 1, the thickness T _t of the lead terminals 4 and 5 is proposed to satisfy the relationship of about 1.026T _t <2T _s <10T _{t. In} the invention described in Patent Document 2, It is proposed that the thickness T _s of the sealant layers 13 and 23 satisfies the relationship of 1.0T _t <2T _s .

However, when the thickness T _t of the lead terminals 4 and 5 is larger than 0.15 mm as described above, the combined thickness 2T _s of the upper and lower sealant layers 13 and 23 is the thickness T of the lead terminals 4 and 5. _{When t} is exceeded, the thickness T _s of each sealant layer 13, 23 becomes extremely thick. Therefore, the sealant layers 13, 23 are formed on the end surfaces of the heat-welded portions 1 b, 2 b where the upper and lower aluminum laminate sheets 1, 2 overlap. The end face of this will be exposed widely. The end face exposed to the outside leads to the inside of the aluminum laminate sheets 1 and 2 through only the resin of the sealant layers 13 and 23 without passing through the barrier metal layers 12 and 22, and thus the layer thickness of this end face As the thickness increases, the barrier properties decrease. In particular, in the case of a non-aqueous electrolyte secondary battery, gas is generated when moisture enters the inside, so that a certain barrier property against moisture is required. Therefore, when the thickness T _t of the lead terminals 4 and 5 exceeds 0.15 mm, the inventions of Patent Documents 1 and 2 cannot be adopted.
Japanese Patent Laid-Open No. 11-329397 JP 2000-173560 A

  The present invention has a problem that when the lead terminal is very thick, sealing by heat welding of the laminate sheet may be insufficient, or the lead terminal may contact the barrier metal layer of the laminate sheet and cause a short circuit. Is to solve.

According to a first aspect of the present invention, there is provided a battery in which a power generating element is housed in an exterior body made of a laminate sheet having a thermoplastic resin layer formed inside a metal layer, and the lead terminal is drawn out from a joint portion between the exterior bodies. the thickness _{T t} together with used within the scope of 0.15mm _<T t _<0.5mm of thickness _{T s} of the thermoplastic resin layer is a relationship of 0.8T _{t <2T} s <1.0T _t It is characterized by satisfying.

According to the invention of claim 1, since the thickness 2T _s of the thermoplastic resin layer of the laminate sheet has a sufficient thickness exceeding 80% of the thickness T _t of the lead terminal, the thickness T _t is 0.15 mm. Even if an extremely thick lead terminal of ˜0.5 mm is sandwiched between the laminate sheets and thermally welded, the resin of the thermoplastic resin layer melts and sufficiently wraps around the side surface of the lead terminal and can be reliably sealed. It becomes like this. In addition, since the thermoplastic resin layer has a sufficient thickness, there is no possibility that the lead terminal and the metal layer come into contact with each other to cause a short circuit because the layer thickness becomes too thin due to melting of the thermal welding. Further, since the thickness 2T _s of both the thermoplastic resin layers is made thinner than the thickness T _t of the lead terminal, the layer thickness exposed on the end face of the laminate sheet becomes too thick and the barrier property is lowered. There is no such thing.

  Hereinafter, the best embodiment of the present invention will be described.

  In the present embodiment, a nonaqueous electrolyte secondary battery in which the power generation element 3 is housed between two aluminum laminate sheets 1 and 2 will be described as in the conventional example. As shown in FIG. 1, the aluminum laminate sheets 1 and 2 used as the exterior body of the nonaqueous electrolyte secondary battery are also composed of base film layers 11 and 21, barrier metal layers (metal layers) 12 and 22, and a sealant layer ( It is a flexible sheet in which thermoplastic resin layers 13 and 23 are laminated in a laminate. Since the base film layers 11 and 21 cover the outermost layers of the aluminum laminate sheets 1 and 2 as the exterior body of the nonaqueous electrolyte secondary battery, a strong resin such as nylon resin or PET (polyethylene terephthalate) is used. Used. However, the base film layers 11 and 21 can have any configuration as long as the strength of the sheet can be ensured, and other resins or other than resins can be used. You can also use the The barrier metal layers 12 and 22 are metal layers for ensuring a barrier property against moisture, gas, and the like that are insufficient only with a resin, and an aluminum vapor deposition film or the like can be used in addition to an aluminum foil. In particular, in a non-aqueous electrolyte secondary battery, gas is generated when moisture enters the inside, so that a certain barrier property against moisture is required, and a barrier property against non-aqueous electrolyte is also required. The sealant layers 13 and 23 are layers that are made of a thermoplastic resin such as PP (polypropylene) or PE (polyethylene), which are superposed and thermally welded to be sealed. However, in this embodiment, as will be described later, the thickness of the sealant layers 13 and 23 is larger than that of the conventional one.

  As shown in FIG. 2 and FIG. 3, the two aluminum laminate sheets 1 and 2 are used by overlapping the same size of a square with each other so that the sealant layers 13 and 23 are in contact with each other. In addition, these two aluminum laminate sheets 1 and 2 are formed in accordance with the shape of the power generation element 3 accommodated therebetween, and the power generation element storage portions 1a and 2a whose inner surface side is recessed in a concave shape by drawing in advance in the center of the center in advance. Is formed. That is, the upper aluminum laminate sheet 1 is formed with a power generation element storage portion 1 a that is concave upward from the lower surface with the sealant layer 13. The lower aluminum laminate sheet 2 has an upper surface with the sealant layer 23. A power generation element storage portion 2a having a concave shape from the bottom to the bottom is formed. However, if the power generation element storage portions 1a and 2a have the same shape, the two aluminum laminate sheets 1 and 2 can be used as common parts. Such power generation element storage portions 1a and 2a may be formed only on one of the upper and lower aluminum laminate sheets 1 and 2, and if the power generation element 3 is sufficiently thin, it may not be formed on both. Also good.

  The power generation element 3 of the non-aqueous electrolyte secondary battery according to the present embodiment uses a positive electrode and a negative electrode wound in a cylindrical shape through a separator and is crushed from the side surface and formed into a flat long cylindrical shape. Yes. The positive electrode is obtained by applying a positive electrode active material to the surface of a strip-shaped aluminum foil, and the negative electrode is obtained by applying a negative electrode active material to the surface of a strip-shaped copper foil. However, when the positive electrode and the negative electrode are provided with an uncoated portion of the active material on the belt-like side edge portion and wound as the power generation element 3, the positive electrode and the negative electrode are formed at the front end portion in the winding axis direction (front-rear direction). The aluminum foil that is the uncoated portion of the positive electrode is protruded, and the copper foil that is the uncoated portion of the negative electrode is protruded from the rear end portion. The aluminum foil protruding on the front end face of the power generating element 3 is ultrasonically welded to the rear base of the positive electrode lead terminal 4, and the copper foil protruding on the rear end face is connected to the front of the negative electrode lead terminal 5. The base of is ultrasonically welded. The positive electrode lead terminal 4 is made of a strip-shaped aluminum foil or the like, and the negative electrode lead terminal 5 is made of a strip-shaped copper foil or the like. Therefore, in the power generating element 3, the tip end portion of the positive electrode lead terminal 4 protrudes further forward from the front end face, and the tip end portion of the negative electrode lead terminal 5 protrudes further rearward from the rear end face. Become.

In the present embodiment, as shown in FIG. 1, the thickness of the aluminum foil or copper foil of the lead terminals 4 and 5 is made extremely thicker than that of the conventional example. That is, the lead terminals 4 and 5 have a thickness T _{t that} is greater than 0.15 mm and less than 0.5 mm (0.15 mm <T _t <0.5 mm). When the lead terminals 4 and 5 are thickened in this way, the cross-sectional area becomes large and the current capacity can be increased, so that a large current can be taken out from the power generation element 3. In general, when the battery capacity of the power generating element 3 is increased, the charge / discharge current is often increased. Therefore, it is necessary to increase the current capacity by increasing the thickness of the lead terminals 4 and 5 as described above. However, even if the power generation element 3 has the same volume and the same battery capacity, a large current can be taken out by thinly applying the active material of the positive electrode and the negative electrode to increase the number of turns and increase the facing area. In addition, it is necessary to increase the current capacity by increasing the thickness of the lead terminals 4 and 5. Further, when the lead terminals 4 and 5 are made thicker in this way, the electrical resistance of the lead terminals 4 and 5 is reduced, so that the charge / discharge current loss can be reduced and the charge / discharge efficiency can be increased. Further, since the mechanical strength of the lead terminals 4 and 5 itself is increased, even when the battery receives vibration or impact from the outside and a strong stress or the like is applied to these lead terminals 4 and 5, it is difficult to break. it can.

Aluminum laminate sheet 1 of this embodiment, corresponding to very thick lead terminals 4 and 5 described above, the thickness T of each of the thickness T _s of the lead terminals 4 and 5 of the sealant layer 13 and 23 _It is thicker than 40% and thinner than 50% of _t . That is, as shown in FIG. 1, the lead terminals 4 and 5 are sandwiched between the sealant layers 13 and 23 of the upper and lower aluminum laminate sheets 1 and 2, so that the sealant layer 13 of the upper aluminum laminate sheet 1 of a thickness _{T s} and the thickness of 2T _s plus the thickness _{T s} and below the aluminum laminate sheet 2 of the sealant layer 23 is thinner than 100% greater than 80% of the thickness _{T t} of the lead terminals 4 and 5 are to _{(0.8T t <2T s <1.0T} t).

  The power generation element 3 is fitted and stored in the power generation element storage portions 1a and 2a between the two upper and lower aluminum laminate sheets 1 and 2. Therefore, as shown in FIGS. 2 and 3, the upper and lower aluminum laminate sheets 1 and 2 have peripheral edges that overlap with each other with the power generation element 3 interposed therebetween. In addition, the lead terminals 4 and 5 of the power generation element 3 are drawn out from the interval where the front and rear peripheral portions of the upper and lower aluminum laminate sheets 1 and 2 overlap each other. When the aluminum laminate sheets 1 and 2 are overlapped in this manner, the peripheral edge is heated while pressing from above and below. Then, since the upper and lower sealant layers 13 and 23 are melted and thermally welded, the peripheral portions of the two aluminum laminate sheets 1 and 2 are integrated into the heat welded portions 1b and 2b over the entire circumference, thereby generating power. The interior in which the element 3 is stored is sealed. In addition, since the sealant layers 13 and 23 are melted with the lead terminals 4 and 5 sandwiched between the two aluminum laminate sheets 1 and 2 at the front and rear heat welded portions 1b and 2b, these lead terminals 4 and 5 Can be sealed in a state of being pulled out from the inside to the outside.

  Actually, the heat-welded portions 1b and 2b at the peripheral portions of the aluminum laminate sheets 1 and 2 are not thermally welded all at once, but only a part of the peripheral portion is left open as a liquid injection port. A non-aqueous electrolyte is poured from here. The liquid injection port is sealed by thermal welding after precharging the nonaqueous electrolyte secondary battery. Further, as shown in FIGS. 2 and 3, the lead terminals 4 and 5 are preliminarily bonded to the aluminum laminate sheets 1 and 2 in order to ensure that the interface between the metal and the resin is familiar and sealed during the heat welding. A thin tab film 6 is thermally welded to the sandwiched portion. This is because the tab film 6 is sufficiently heated in advance on the surfaces of the lead terminals 4 and 5 so as to be surely heat-welded. This is to prevent the possibility that the metal and the sealant layers 13 and 23 are not sufficiently mixed with each other. That is, the heat welding condition of the aluminum laminate sheets 1 and 2 is basically set to a pressing force and a temperature (heat amount) so that the overlapping sealant layers 13 and 23 are surely welded to each other. If the lead terminals 4 and 5 having good conductivity are sandwiched, the temperature for sufficiently adapting to the metal surface may be insufficient. However, if the tab film 6 is sufficiently familiar with the metal surface in advance, it is easy for the sealant layers 13 and 23 to be familiar and welded to the tab film 6, so that the temperature does not become insufficient. The tab film 6 is made of the same thermoplastic resin as the sealant layers 13 and 23. However, since the tab film 6 is extremely thin, the cross-sectional view is omitted in FIGS. 1 and 4.

As a result of the above heat welding, as shown in FIG. 1, the sealant layers 13 and 23 of the upper and lower aluminum laminate sheets 1 and 2 are fused and adhered to the upper and lower surfaces of the strip-like aluminum foil or copper foil of the lead terminals 4 and 5. Sealed. In addition, the left and right sides of these lead terminals 4 and 5 are directly welded so that the upper and lower sealant layers 13 and 23 overlap each other, so that these portions are also sealed reliably. Moreover, these sealant layers 13 and 23, since the thickness 2T _s plus respective thickness _{T s} is greater than 80% of the thickness _{T t} of the lead terminals 4 and 5, molten resin is of lead The side edges of the lead terminals 4 and 5 can be reliably sealed by sufficiently surrounding the left and right side surfaces of the terminals 4 and 5. Further, since the sealant layers 13 and 23 have a sufficient thickness, the lead terminals 4 and 5 can be used as a barrier metal layer even if the layer thickness is somewhat reduced due to melting during heat welding. There is no risk of contact with 12 or 22. Furthermore, these sealant layers 13 and 23, since the thickness 2T _s tailored both are set to be thinner than the thickness T _t of the lead terminals 4 and 5, heat seal parts 1b, exposed at the end face of 2b The thickness T _s of the sealant layers 13 and 23 to be increased is not excessively increased and the barrier property is not deteriorated. In FIG. 1, the thickness T _s of the sealant layers 13 and 23 is shown to be the same as that of the other portions in the heat welded portions 1b and 2b. It is thin to some extent.

  In addition, although the case where the two aluminum laminate sheets 1 and 2 were overlapped was shown in the above embodiment, for example, one aluminum laminate sheet is folded in two, or overlapped at both ends and the central portion like an envelope. While doing so, the power generation element may be accommodated, or the power generation element may be accommodated in an aluminum laminate sheet that has been formed into a bag shape in advance. When the aluminum laminate sheet is overlapped and thermally welded at the end other than the peripheral portion in this way, the lead terminals 4 and 5 may be pulled out from the heat welded portion at the end other than the peripheral portion. Good. Furthermore, in the said embodiment, although the case where the aluminum laminate sheet using aluminum foil, an aluminum vapor deposition film, etc. was used for barrier metal layers 12 and 22 was shown, if it is a laminate sheet which can secure barrier property, The metal material of the barrier metal layers 12 and 22 is arbitrary.

  Moreover, in the said embodiment, although the winding type electric power generation element 3 shape | molded by the long cylindrical shape was shown, the structure of this electric power generation element 3 is arbitrary, and what was wound by the long cylindrical shape or the ellipse from the beginning is used. It can also be used, or a laminated type can be used, and it does not necessarily have to be flat. Furthermore, although the case where the lead terminals 4 and 5 are pulled out from both end faces of the power generating element 3 is shown in the above embodiment, the positive and negative electrode lead terminals 4 and 5 may be pulled out from both end faces. It can also be pulled out from a portion other than the end face, for example, the winding end portion of the electrode.

  In the above embodiment, a non-aqueous electrolyte secondary battery that requires a particularly reliable barrier property against moisture is shown, but a high barrier property against gas, moisture, and the like is also required for other batteries. The type of this battery is not necessarily limited.

In the nonaqueous electrolyte secondary battery of the above embodiment, the thickness T _t of the lead terminals 4 and 5 is 0.3 mm, and the thickness T _s of the sealant layers 13 and 23 of the aluminum laminate sheets 1 and 2 is 0.105 mm ( 0.7T _t = 2T _s ) and 0.165 mm (1.1 _{T t} = 2T _s ), and two types of comparative examples, and the thickness T _s of the sealant layers 13 and 23 is 0.135 mm (0.9T _t = As a result of comparison with the example of 2T _s ), in the comparative example in which the thickness T _s of the sealant layers 13 and 23 is 0.105 mm, sealing is incomplete because the sealant layers 13 and 23 are thin. In some cases, the lead terminals 4 and 5 may come into contact with the barrier metal layers 12 and 22. In the comparative example in which the thickness T _s of the sealant layers 13 and 23 is 0.165 mm, this barrier metal layer is used. 12 and 22 are thick The While moisture barrier properties had in too low, in the embodiment in which the thickness T _s of the sealant layer 13 and 23 and 0.135 mm, the lead terminals 4 and 5 with sufficient sealing and barrier properties can be obtained Did not come into contact with the barrier metal layers 12 and 22.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partially enlarged longitudinal sectional view of a lead terminal lead-out portion in a nonaqueous electrolyte secondary battery using an aluminum laminate sheet as an exterior body, showing an embodiment of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment of the present invention, and is an exploded perspective view in which a part of a heat welding part 1 in a nonaqueous electrolyte secondary battery using an aluminum laminate sheet as an exterior body is opened. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a nonaqueous electrolyte secondary battery using an aluminum laminate sheet as an exterior body according to an embodiment of the present invention. FIG. 9 is a partial enlarged longitudinal sectional view of a lead terminal lead-out portion in a nonaqueous electrolyte secondary battery using an aluminum laminate sheet as an exterior body, showing a conventional example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Aluminum laminate sheet 12 Barrier metal layer 13 Sealant layer 2 Aluminum laminate sheet 22 Barrier metal layer 23 Sealant layer 3 Power generation element 4 Positive electrode lead terminal 5 Negative electrode lead terminal

Claims (1)

In a battery in which a power generation element is housed in an exterior body made of a laminate sheet in which a thermoplastic resin layer is formed inside a metal layer, and lead terminals are drawn out from a joint portion between the exterior bodies,
Lead terminal thickness T _t is 0.15 mm <T _t <0.5 mm
With use within the scope of, the thickness _{T s} of the thermoplastic resin layer is 0.8T _{t <2T} s <1.0T _t
A battery characterized by satisfying the above relationship.

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