JP2006107894A - Battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a battery capable of surely preventing leakage of electrolyte at protruded parts of lead terminals 3, 4 on welding parts 21b, 22b of aluminum laminate films 21, 22, by covering the lead terminals 3, 4 with covering materials 5, 6 and polymeric absorption films 7, 8. <P>SOLUTION: On the battery, a battery case is formed by superimposing two sheets of aluminum laminate films 22 and heat-welding peripheral welding parts 21b, 22b, and the lead terminals 3, 4 protruded from an element 1 housed in the battery case 2 are drawn outside through the welding parts 21b, 22b. Sealing parts 3a, 4a of the lead terminals 3, 4 interposed between the welding parts 21b, 22b are covered with the welded covering materials 5, 6 made of thermoplastic resin, and the covering materials 5, 6 are covered with thermally welded polymeric absorption films 7, 8. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a battery using a battery case made of a flexible film such as an aluminum laminate film.

  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 an element 1 is composed of two rectangular aluminum laminate films 21 and 22. The element 1 is a power generation element in which a belt-like positive electrode and a negative electrode are wound through a separator to form an elongated cylinder, and the positive electrode lead terminal 3 and the negative electrode lead terminal 4 are projected from both end surfaces. The positive electrode lead terminal 3 is made of a strip-shaped aluminum foil, and the base is connected to the positive electrode of the element 1. The negative electrode lead terminal 4 is made of a strip-shaped copper foil, and the base is connected to the negative electrode of the element 1.

  The two aluminum laminate films 21 and 22 constituting the battery case 2 have a base film layer made of a resin having a high barrier property or strength such as nylon or PET (polyethylene terephthalate) on one surface of a metal layer made of aluminum foil. It is a three-layer rectangular flexible laminate film in which a sealant layer made of a thermoplastic resin such as polypropylene or polyethylene is laminated on the other surface while being laminated. In addition, these aluminum laminate films 21 and 22 are provided with concave portions 21a and 22a in which the surface on the sealant layer side is recessed by drawing in the center in advance so that the long cylindrical element 1 can be fitted. Is formed. The two aluminum laminate films 21 and 22 are overlapped with the sealant layers facing each other, and the element 1 is fitted into the space formed by the recesses 21a and 22a, and after filling the electrolyte, By thermally welding the welded portions 21b and 22b, the battery case 2 with the inside sealed is obtained.

  The lead terminals 3 and 4 projecting from the element 1 are sealed through the overlap of the two aluminum laminate films 21 and 22 at the peripheral welded portions 21b and 22b, and project outside the battery case 2. ing. Further, these lead terminals 3 and 4 are obtained by thermally welding the covering materials 5 and 6 in advance to the sealing portions 3a and 4a that are to be interposed between the welded portions 21b and 22b of the aluminum laminate films 21 and 22, respectively. ing. The covering materials 5 and 6 completely cover the sealing portions 3a and 4a of the lead terminals 3 and 4 with two square sheets made of the same thermoplastic resin as the sealant layers of the aluminum laminate films 21 and 22, respectively. It is what was heat-welded on both sides. Accordingly, the welded portions 21 b and 22 b of the aluminum laminate films 21 and 22 are sealed by thermally welding the sealing portions 3 a and 4 a of these lead terminals 3 and 4 via the covering materials 5 and 6.

  Here, when the lead terminals 3 and 4 are directly heat-sealed between the welded portions 21b and 22b of the aluminum laminate films 21 and 22, the metal material of the lead terminals 3 and 4 and the resin material of the sealant layer are originally Is not easy to get used to, and the adhesion tends to be insufficient, and the lead terminals 3 and 4 made of a metal material with good thermal conductivity such as aluminum foil and copper foil are deprived of heat, and only the welding temperature of that portion is lowered. Therefore, sealing at these interfaces may be incomplete. Therefore, as described above, by thermally welding the covering materials 5 and 6 to the lead terminals 3 and 4 in advance in a separate process, it is possible to set conditions such as an optimum welding temperature and pressure. The interface between the covering materials 5 and 6 and the lead terminals 3 and 4 is surely sealed. Further, if the covering materials 5 and 6 are heat-welded in advance to the lead terminals 3 and 4 in this way, the same kind of resin can be used even when the welding portions 21b and 22b of the aluminum laminate films 21 and 22 are heat-welded. Since the sealant layer made of the material and the covering materials 5 and 6 are easily adapted, sufficient sealing can be performed.

  However, even in the conventional non-aqueous electrolyte secondary battery, for example, when it is left for a long time in a high temperature environment, the gas generated by the decomposition of the non-aqueous electrolyte increases the internal pressure of the battery. There was a problem that leakage occurred from the protruding portions of the lead terminals 3 and 4 in the welded portions 21b and 22b of the aluminum laminate films 21 and 22 to reduce the battery capacity and corrode external wiring. .

  In order to prevent moisture from entering the battery from the outside through the protruding portions of the lead terminals 3 and 4 in the welded portions 21b and 22b of the aluminum laminate films 21 and 22, a part of the covering materials 5 and 6 is used. Or the invention which comprised all by the penetration prevention member is proposed conventionally (for example, refer to patent documents 1). However, all the covering materials 5 and 6 are conventionally made of polyethylene, and in this case, the above problem cannot be solved. Further, even when all of the covering materials 5 and 6 are made of a thermoplastic resin containing a moisture absorbent, silica gel, activated carbon, zeolite, etc. used as the moisture absorbent inhibit the adhesion with the lead terminals 3 and 4. Therefore, it is difficult to reliably perform sealing. Furthermore, even when all of the covering materials 5 and 6 are made of a material capable of adsorbing and removing moisture, it is difficult to reliably bring such special material and the lead terminals 3 and 4 into close contact with each other. Furthermore, the covering materials 5 and 6 are divided along the longitudinal direction of the lead terminals 3 and 4 into a portion made of a close contact member and a portion made of a permeation prevention member (FIGS. 1 to 5 of Patent Document 1), When the permeation preventing members are interspersed (FIG. 6 of Patent Document 1), the structure of the covering materials 5 and 6 becomes complicated, and the manufacture is not easy or the manufacturing cost is too high.

In addition, since the invention of Patent Document 1 is to prevent moisture from entering the inside of the battery through the layers of the covering materials 5 and 6 (paragraph number “0019” of Patent Document 1), The lead terminals 3 and 4 and the aluminum laminate films 21 and 22 are always arranged so as to be in contact with each other. However, the leakage of the non-aqueous electrolyte, which is a problem in the above, actually leaks from the interface between the coating materials 5 and 6 and the welded portions 21b and 22b of the aluminum laminate films 21 and 22. There are many. This is because the coating materials 5 and 6 are heat-welded in advance to ensure the close contact between the metal material of the lead terminals 3 and 4 and the resin material of these coating materials 5 and 6, but the aluminum laminate film 21 , 22, the problem that the lead terminals 3 and 4 are deprived of heat and only the welding temperature is lowered cannot be completely solved at the time of thermal welding of the welding parts 21 b and 22 b of the welding parts 21 b and 22 b. Compared with other parts where the sealant layers are heat-welded, the part where the covering materials 5 and 6 are interposed inevitably decreases the welding strength, and the internal pressure of the battery rises and a strong pressure is applied. This is because the risk of insufficient sealing at the interface with the materials 5 and 6 cannot be completely avoided. Therefore, the invention of Patent Document 1 is an inefficient structure for preventing the nonaqueous electrolyte from leaking out from the interface between the covering materials 5 and 6 and the welded portions 21b and 22b of the aluminum laminate films 21 and 22. However, there are disadvantages such as high cost despite the fact that the effect is small. Furthermore, since the invention of Patent Document 1 prevents moisture permeation, it may not be possible to prevent permeation of a nonaqueous electrolytic solution made of an organic solvent.
JP 2004-39358 A

  The present invention provides a battery capable of reliably preventing leakage of electrolyte at the protruding portion of the lead terminal in the welded portion of the flexible film by covering the covering material and protruding portion of the lead terminal with the polymer absorbent material. Is to provide.

  According to the first aspect of the present invention, a battery case is formed by superimposing a flexible film having at least an inner surface made of a thermoplastic resin and thermally welding a peripheral portion thereof, and a lead terminal protruding from an element accommodated in the battery case is flexible. In a battery drawn out through the heat-sealed and superposed film, the lead terminal sealing portion interposed between the superposed flexible films is a heat-welded thermoplastic resin covering material In addition, the covering material is covered with a polymer absorbent film made of a thermally welded thermoplastic resin.

  According to the invention of claim 2, a battery case is formed by superposing a flexible film having at least an inner surface made of a thermoplastic resin and thermally welding a peripheral portion thereof, and a lead terminal protruding from an element accommodated in the battery case is flexible. In a battery drawn out through the heat-sealed and superposed film, the lead terminal sealing portion interposed between the superposed flexible films is a heat-welded thermoplastic resin covering material The lead terminal covered with the covering material is covered with a polymer absorbent body made of a thermoplastic resin.

  According to the invention of claim 1, since the sealing portion of the lead terminal is sealed to the welded portion of the flexible film via the covering material and the polymer absorber film, the electrolysis inside the battery case is caused by an increase in the battery internal pressure or the like. Even if the liquid tries to ooze out between the covering material and the welded portion of the flexible film, the electrolytic solution is absorbed by the polymer absorber film, so that it does not leak to the outside. Polymer absorbent film made of thermoplastic resin is a film of thermoplastic resin that can absorb and retain a large amount of electrolyte by adsorbing water-soluble or non-aqueous electrolyte into the molecular structure to form a gel. It is.

  According to the invention of claim 2, since the projecting portion from the flexible film in the lead terminal is covered with the polymer absorber, the electrolyte inside the battery case is caused to rise from the welded portion between the coating material and the flexible film due to an increase in the battery internal pressure or the like Even if the electrolyte solution oozes out to the outside, the electrolyte solution is absorbed by the polymer absorber, so that it does not leak to the outside. The polymer absorber is a thermoplastic resin similar to the polymer absorber film of claim 1 and may be in the form of a film or simply attached and covered.

  In addition, it is preferable to use the laminated film which laminated | stacked the thermoplastic resin layer, the metal layer, and the resin layer from the inner surface side for the said flexible film. Thus, when the laminated film which laminated | stacked the metal layer and the resin layer on the outer side of the thermoplastic resin layer is used, the barrier property of a battery case can be made extremely high.

  Hereinafter, the best embodiment of the present invention will be described with reference to FIGS. 1 to 2, the same reference numerals are given to the constituent members having the same functions as those of the conventional example shown in FIG.

  In the present embodiment, a non-aqueous electrolyte secondary battery using an aluminum laminate film as a battery case will be described as in the conventional example. The configuration of the battery case 2 and the element 1 of this nonaqueous electrolyte secondary battery is the same as that of the conventional example shown in FIG. As shown in FIG. 1, the same covering materials 5 and 6 as those in the conventional example are thermally welded to the sealing portions 3 a and 4 a of the lead terminals 3 and 4 protruding from both end faces of the element 1. The covering materials 5 and 6 are made of a thermoplastic resin such as polypropylene and polyethylene similar to the sealant layers of the aluminum laminate films 21 and 22, and the lead terminals 3 and 4 are provided between two sheets of such thermoplastic resin. Or by welding the lead terminals 3 and 4 while the sheet material is folded in half, or by inserting the lead terminals 3 and 4 into the cylindrical sheet material. The sealing portions 3a and 4a are covered by heat welding. In addition, since the covering materials 5 and 6 made of such a thermoplastic resin can set conditions such as optimum welding temperature and pressure for the metal lead terminals 3 and 4, sealing at the interface is possible. Can be ensured.

  In this embodiment, the polymer absorbent films 7 and 8 are further thermally welded so as to completely cover the covering materials 5 and 6 that are thermally welded to the sealing portions 3a and 4a of the lead terminals 3 and 4. Here, the polymer absorber films 7 and 8 are made of polyethylene oxide (PEO: PolyEthyleneOxide) having a three-dimensional network molecular structure by crosslinking treatment. Since the polymer absorber films 7 and 8 are formed into a gel by adsorbing an organic solvent or an aqueous solution to the three-dimensional network structure, they can absorb and hold a large amount of the electrolytic solution. However, since the polymer absorbent films 7 and 8 adsorb the electrolyte solution by the three-dimensional network molecular structure formed by the cross-linking treatment, a high-temperature and high-pressure is applied while maintaining this molecular structure. It is difficult to reliably heat-weld the lead terminals 3 and 4. For this reason, first, the same covering materials 5 and 6 as those in the prior art are thermally welded to the sealing portions 3a and 4a of the lead terminals 3 and 4, and the polymer absorbent film 7 made of the same resin is attached to the covering materials 5 and 6. , 8 are heat-welded.

  The element 1 in which the covering materials 5 and 6 and the polymer absorbent films 7 and 8 are heat-welded to the sealing portions 3a and 4a of the lead terminals 3 and 4 as described above has two aluminum laminate films 21 and 22 attached thereto. The battery case 2 is fitted into a space formed by the recesses 21a and 22a formed to overlap each other, and the peripheral welds 21b and 22b are thermally welded after the electrolyte solution is filled, as shown in FIG. Sealed inside. In addition, the lead terminals 3 and 4 have sealing portions 3a and 4a of the welded portions 21b and 22b of the two aluminum laminate films 21 and 22 through the covering materials 5 and 6 and the polymer absorber films 7 and 8, respectively. The sealant layer and the polymer absorbent films 7 and 8 are sealed by being sandwiched between the sealant layers and the polymer absorbent films 7 and 8 when the weld portions 21b and 22b are thermally welded.

  According to the above configuration, when the nonaqueous electrolyte secondary battery is left in a high temperature environment for a long time, the internal pressure of the battery rises, and the nonaqueous electrolyte is welded between the coating materials 5 and 6 and the aluminum laminate films 21 and 22. Even if it is about to ooze out through the space between 21b and 22b, the non-aqueous electrolyte is absorbed and held in the polymer absorber films 7 and 8, so that it does not leak out. Therefore, by preventing leakage of the non-aqueous electrolyte, it is possible to prevent the wiring outside the battery from being corroded. Further, since the polymer absorbent films 7 and 8 absorb the absorbed non-aqueous electrolyte into the molecular structure to form a gel, the polymer absorbent films 7 and 8 are further non-aqueous like when they are soaked into a fibrous or porous member. This non-aqueous electrolyte can be prevented from exuding further without continuously sucking the electrolyte. Accordingly, not only the leakage of the nonaqueous electrolyte solution to the outside but also the decrease of the nonaqueous electrolyte solution in the battery case 2 can be prevented, so that the battery capacity can be prevented from decreasing. .

  In addition, although the case where polyethylene oxide was used as the polymer absorber films 7 and 8 was shown in the said embodiment, this material will not be limited if it is a thermoplastic resin which adsorb | sucks electrolyte solution and becomes a gel. As the polymer absorber film made of such a thermoplastic resin, it is preferable to use a resin material disposed between the electrodes of the polymer battery. In addition to the polyethylene oxide of this embodiment, for example, polyvinylidene fluoride ( PVDF: PolyVinyliDeneFluoride) or polyvinyl alcohol (PVA: PolyVinylAlcohol) can also be used. However, polyethylene oxide can absorb not only the non-aqueous electrolyte shown in the present embodiment but also a water-soluble electrolyte, but since polyvinylidene fluoride is hydrophobic, a water-soluble electrolyte is used. It cannot be used for the battery used.

  Moreover, in the said embodiment, although the polymer absorber films 7 and 8 showed the case where the coating | covering materials 5 and 6 were covered completely, this coating | covering material 5 over the perimeter of the longitudinal direction of the lead terminals 3 and 4 at least. , 6 need only be covered with the polymer absorber films 7, 8, and therefore it is not always necessary to completely cover the lead terminals 3, 4 to the base side or the tip side in the longitudinal direction. In particular, when the polymer absorbent films 7 and 8 completely cover the covering materials 5 and 6 on the base side of the lead terminals 3 and 4, the amount of protrusion to the inside of the battery case 2 increases. Therefore, it is not necessary to completely cover the covering materials 5 and 6 on the base side.

  In the above embodiment, the covering materials 5 and 6 covering the sealing portions 3a and 4a of the lead terminals 3 and 4 are further covered with the polymer absorber films 7 and 8, and then the welded portions of the aluminum laminate films 21 and 22 are covered. As shown in FIG. 3, first, the sealing portions 3a and 4a of the lead terminals 3 and 4 are covered with the covering materials 5 and 6, and then the aluminum laminate films 21 and 22 are bonded. The welded portions 21b and 22b are thermally welded (the configuration up to here is the same as that of the conventional example shown in FIG. 4), and the portions where these lead terminals 3 and 4 protrude from between the welded portions 21b and 22b are polymer absorbers. It can also be covered with layers 9 and 10. Here, when the end portions of the covering materials 5 and 6 protrude along with the lead terminals 3 and 4 from between the welded portions 21b and 22b, the polymer absorber layers 9 and 10 are at least these covering materials 5 and 6, respectively. 6 and the welded portions 21b and 22b need to be reliably covered with the polymer absorbent layers 9 and 10, and as shown in FIG. You may make it cover all. However, when the covering materials 5 and 6 do not protrude from between the welded portions 21b and 22b, the boundaries between the lead terminals 3 and 4 and the welded portions 21b and 22b are surely covered with the polymer absorber layers 9 and 10. What should I do? The polymer absorber layers 9 and 10 are made of the same polymer absorber material as the polymer absorber films 7 and 8, but it is not always necessary to thermally weld the film-like material, as shown in FIG. The polymer absorber material melted by heat can be coated on the protruding portions of the lead terminals 3 and 4 so as to be covered in layers.

  Moreover, in the said embodiment, although the recessed part 21a, 22a was previously formed in the two aluminum laminate films 21 and 22, respectively, and the case where the element 1 was engage | inserted here was shown, any one aluminum laminate film 21, It is also possible to form a recess only in 22 or not to form a recess in any of the aluminum laminate films 21 and 22. Furthermore, although the case where the two aluminum laminate films 21 and 22 are overlapped to form the battery case 2 is shown in the above embodiment, the configuration of the battery case 2 is arbitrary, for example, one aluminum laminate film Can be folded in half to form the battery case 2. Furthermore, in the said embodiment, although the case where an aluminum laminated film was used for a battery case was shown, it replaced with aluminum foil and the metal and resin laminated film using the metal layer which has another barrier property can also be used. Furthermore, any material can be used as long as it is a flexible film that ensures sufficient strength and barrier properties and can be reliably sealed. For example, a flexible film made of only a resin that is not a laminate film can be used. However, since this flexible film is sealed by heat welding, when using a laminate film, the inner surface layer must be a thermoplastic resin. If not, the entire flexible film is heated. It must be a plastic resin.

  Moreover, although the said embodiment demonstrated the nonaqueous electrolyte secondary battery, if a polymer absorber material is selected appropriately, it can implement similarly to the battery using water-soluble electrolyte solution. Furthermore, the present invention can be similarly applied to a primary battery as well as a secondary battery. Furthermore, the secondary battery referred to here is not limited to a chemical battery using a power generation element as an element, but also includes a battery using an electric double layer capacitor or the like that accumulates electric charge for the element.

  100 cells each of the nonaqueous electrolyte secondary battery (Example) using the polymer absorbent films 7 and 8 shown in the above embodiment and the nonaqueous electrolyte secondary battery (Comparative Example) shown in the conventional example. As a result of measuring the decrease in battery capacity when left for one month in an environment at a temperature of 60 ° C., there was no battery capacity that decreased to less than 80% in the examples, but in the comparative example, the battery capacity was 80%. There were 4 cells that had fallen below. Therefore, it was confirmed that the use of the polymer absorbent films 7 and 8 can prevent a decrease in battery capacity due to leakage of the non-aqueous electrolyte even when left for a long time in a high temperature environment.

  In addition, as a result of performing cycle life tests on the nonaqueous electrolyte secondary batteries of the above examples and comparative examples in a room temperature environment several cells at a time, in the case of the comparative example, the battery capacity is 80 in about 500 cycles. On the other hand, in the example, the battery capacity exceeded 80% until about 1000 cycles. Therefore, it was confirmed that the cycle life of the secondary battery was improved by using the polymer absorbent films 7 and 8.

1 is an exploded perspective view showing a configuration of a nonaqueous electrolyte secondary battery according to an embodiment of the present invention. 1 shows an embodiment of the present invention and is an overall perspective view of a non-aqueous electrolyte secondary battery. FIG. FIG. 3 is an overall perspective view showing another embodiment of the present invention and showing another configuration of the nonaqueous electrolyte secondary battery. It is a disassembled perspective view which shows a prior art example and shows the structure of a nonaqueous electrolyte secondary battery.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Element 2 Battery case 21 Aluminum laminated film 21b Welding part 22 Aluminum laminated film 22b Welding part 3 Positive electrode lead terminal 3a Sealing part 4 Negative electrode lead terminal 4a Sealing part 5 Coating material 6 Coating material 7 Polymer absorber film 8 Polymer Absorber film 9 Polymer absorber layer 10 Polymer absorber layer

Claims (2)

A battery case is formed by superimposing a flexible film made of a thermoplastic resin on at least the inner surface and thermally welding the peripheral portion, and lead terminals protruding from the elements housed in the battery case are heat-welded and overlapped. In the battery pulled out through the combined space,
The lead terminal sealing portion interposed between the laminated flexible films is covered with a heat-welded thermoplastic resin coating, and a polymer made of the thermoplastic resin with the thermal-welded thermoplastic resin. A battery characterized by being covered with an absorber film. A battery case is formed by superimposing a flexible film made of a thermoplastic resin on at least the inner surface and thermally welding the peripheral portion, and lead terminals protruding from the elements housed in the battery case are heat-welded and overlapped. In the battery pulled out through the combined space,
The sealing portion of the lead terminal interposed between the laminated flexible films is covered with a coating material made of heat-sealable thermoplastic resin, and the lead terminals covered with the coating material overlap the flexible film. A battery characterized in that a portion protruding from the gap is covered with a polymer absorber made of a thermoplastic resin.

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