JP5011928B2 - battery - Google Patents

Description

  The present invention relates to a battery.

  A battery in which a power generation element including a positive electrode plate and a negative electrode plate is housed in a battery container made of a laminate film obtained by laminating a metal foil and a resin film has a feature that it is thin and lightweight. It has been used in the past. As such a battery, for example, a nonaqueous electrolyte secondary battery described in Patent Document 1 is known.

  A positive electrode lead terminal and a negative electrode lead terminal are respectively connected to the positive electrode plate and the negative electrode plate of the battery, and one ends of the positive electrode and the negative electrode lead terminal are led out to the outside of the battery container.

Each lead terminal is sandwiched between two laminate films (hereinafter also referred to as a first laminate film and a second laminate film) at the edge of the battery container, and the lead terminals are arranged in the thickness direction of each lead terminal. The upper and lower surfaces are thermally welded to the first laminate film and the second laminate film, respectively.
JP 2003-308887 A

  By the way, when an internal short circuit occurs in a battery, a thermal runaway reaction of the active material occurs due to rapid heat generation due to the short circuit current, and this thermal runaway reaction may generate a large amount of gas and increase the internal pressure of the battery. . Also, the battery internal pressure may increase by overcharging the battery.

  When the internal pressure of the battery rises due to an internal short circuit or the like, when the upper and lower surfaces of each lead terminal are thermally welded to the first and second laminate films with the same strength, the upper and lower surfaces of the lead terminal and the first And the welding part with the 2nd laminate film peels at once, and there is a possibility that the gas accumulated in the inside and the power generation element may come out at a stretch.

  The present invention has been completed based on the above circumstances, and provides a highly safe battery that prevents the generation of power generation elements and the like when the battery internal pressure increases due to an internal short circuit or the like. Objective.

  As means for achieving the above-mentioned object, the invention of claim 1 is characterized in that a power generation element including a positive electrode plate and a negative electrode plate is overlapped with a first laminate film and a second laminate film, and an edge portion is welded. The positive electrode plate and the negative electrode plate are connected to a positive electrode lead terminal and a negative electrode lead terminal, and the positive electrode lead terminal and the negative electrode lead terminal are connected to the battery. At the edge of the container, it is sandwiched between the first laminate film and the second laminate film, and a part thereof is thermally welded via the resin layer, and is led out from the battery container, and the positive electrode In at least one of the lead terminal and the negative electrode lead terminal, the weld strength with the first laminate film is the weld strength with the second laminate film. Characterized in was configured to remote are weak.

  According to a second aspect of the present invention, in the positive electrode lead terminal and the negative electrode lead terminal according to the first aspect, the weld strength with the first laminate film is greater than the weld strength with the second laminate film. It is also characterized by weakening.

<Invention of Claim 1>
According to the first aspect of the present invention, in at least one of the positive electrode lead terminal and the negative electrode lead terminal, the welding strength between the lead terminal and the first laminate film is weaker than the welding strength between the second laminate film. ing.

  Therefore, in the lead terminal having a difference in welding strength between the two laminate films, when the internal pressure of the battery is increased due to an internal short circuit or the like, the lead terminal is peeled off from the welded portion between the lead terminal and the first laminate film. Since the welded portion between the terminal and the first and second laminate films is prevented from being peeled off at a time, a highly safe battery that prevents the power generation element or the like from popping out can be provided.

<Invention of Claim 2>
According to the second aspect of the present invention, the welding strength between the lead terminal and the first laminate film is weaker than the welding strength between the second laminate film in both the positive electrode and the negative electrode lead terminal.

  Therefore, when the internal pressure of the battery rises, both the positive and negative lead terminals can be peeled from the welded portion between the lead terminal and the first laminate film. It is possible to prevent the welded portion of the laminate film 2 from being peeled off at a time, and to prevent the power generation element and the like from popping out more effectively.

<Embodiment 1>
Hereinafter, Embodiment 1 in which the battery 10 of the present invention is applied to a non-aqueous electrolyte secondary battery (hereinafter also referred to as the battery 10) will be described with reference to FIGS.
As shown in FIG. 1, a battery 10 according to the present embodiment includes an ellipse winding type power generation element 15 and a non-aqueous electrolyte (not shown) housed in a battery container 11 made of a laminate film. The positive electrode lead terminal 16 and the negative electrode lead terminal 17 connected to the power generation element 15 are led out to the outside of the battery container 11 from the opposite edges of the battery container 11.

  The power generation element 15 of the battery of this embodiment is formed by winding a positive electrode plate and a negative electrode plate with a separator interposed between them, and a positive electrode lead terminal 16 and a negative electrode lead terminal 17 are connected to the positive electrode plate and the negative electrode plate, respectively. Yes.

  The positive electrode plate constituting the power generating element 15 includes a positive electrode mixture layer containing a positive electrode active material capable of occluding and releasing lithium ions on both surfaces of a positive electrode current collector formed of a metal such as aluminum. A positive electrode lead terminal 16 is welded to the positive electrode current collector. As a material of the positive electrode lead terminal 16, a metal such as aluminum or nickel can be used.

Examples of transition metal oxides that occlude and release lithium used as the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiNi _1/2 Mn _1/2 O ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ , and MnO. _{2, FeO 2, V 2 O} 5, V 6 O 13, TiO 2, TiS 2 and the like.

  In addition to the positive electrode active material, a conductive agent such as acetylene black, a binder such as polyvinylidene fluoride, and the like can be added to the positive electrode mixture.

  The negative electrode plate has a negative electrode mixture layer containing a negative electrode active material capable of occluding and releasing lithium ions on both sides of a negative electrode current collector formed of a metal such as copper. The negative electrode current collector includes a negative electrode lead The terminal 17 is welded. As a material of the negative electrode lead terminal 17, a metal such as copper or nickel can be used.

Examples of the negative electrode active material include alloys of lithium, such as Al, Si, Pb, Sn, Zn, and Cd, metal oxides such as LiFe ₂ O ₃ , WO ₂ , MoO ₂ , SiO, and CuO, carbon such as graphite and carbon. A material, lithium nitride such as Li ₅ (Li ₃ N), metallic lithium, or a mixture thereof can be used.

  As the separator, a woven fabric, a non-woven fabric, a synthetic resin microporous membrane or the like can be used, and a synthetic resin microporous membrane can be particularly preferably used.

  As the nonaqueous electrolyte, either a nonaqueous electrolyte solution or a solid electrolyte may be used, or a nonaqueous electrolyte may be used in combination.

  The non-aqueous electrolyte is obtained by dissolving an electrolyte salt in a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, γ-butyrolactone, dimethyl carbonate, ethyl methyl carbonate, dioxolane, methyl acetate, and vinylene carbonate. These polar solvents can be used alone or in admixture of two or more.

Examples of the electrolyte salt dissolved in the non-aqueous solvent include LiPF ₆ , LiClO ₄ , LiBF ₄ , LiAsF ₆ , LiCF ₃ CO ₂ , LiCF ₃ (CF ₃ ) ₃ , LiCF ₃ (C ₂ F ₅ ) ₃ , LiCF ₃ SO _3. , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ CF ₂ CF ₃ ) ₂ , LiN (COCF ₃ ) ₂ , LiN (COCF ₂ CF ₃ ) ₂ , LiPF ₃ (CF ₂ CF ₃ ) _3, etc. It can be used alone or in combination of two or more.

  In the present embodiment, the battery container 11 is formed by superposing two laminated films 12 and 13 having a substantially rectangular shape and thermally welding the overlapping edges. As shown in FIG. 2, the laminated films 12 and 13 forming the battery container 11 are formed of an outermost film layer 14A and an aluminum foil laminated on the film layer 14A with a urethane-based adhesive. It has a three-layer structure in which a barrier layer 14B and a heat-welded layer 14C formed inside the barrier layer 14B are sequentially stacked.

  As the material of the film layer 14A, polyethylene terephthalate (PET), nylon, or the like can be used, and as the material of the heat welding layer 14C, polyethylene (PE), polypropylene (PP), or the like can be used.

  Now, at the opposite edges of the battery case 11, a part of the positive electrode lead terminal 16 and the negative electrode lead terminal 17 is sandwiched between the two laminate films 12 and 13 from above and below and thermally welded via the resin layer 18. ing.

  The resin layer 18 is formed by thermal welding with the tab film 18 sandwiched between the lead terminals 16 and 17 and the two laminate films 12 and 13. As the tab film 18 which forms the resin layer 18, what consists of thermoplastic resins, such as polyethylene (PE) or a polypropylene (PP), is used.

  In at least one of the positive electrode lead terminal 16 and the negative electrode lead terminal 17, the laminate film 12 (first laminate film in the present invention) disposed on the upper side in FIG. Is weaker than that of the lower laminate film 13 (second laminate film in the present invention).

  In the present invention, from the viewpoint of more effectively preventing the power generation element or the like from popping out due to an increase in battery internal pressure, the welding strength with the first laminate film 12 is high in both the positive and negative lead terminals 16 and 17. The welding strength with the second laminate film 13 is preferably weaker. Hereinafter, the lead terminals 16 and 17 whose welding strength with the first laminate film 12 is weaker than the welding strength with the second laminate film 13 are referred to as lead terminals 16 and 17 having a welding strength difference.

  In the lead terminals 16 and 17 having a difference in welding strength, if the welding strength between the lead terminals 16 and 17 and the first laminate film 13 is 1, the welding strength between the lead terminals 16 and 17 and the second laminate film 12 is used. Is preferably 1.2 to 1.5. In addition, irrespective of the presence or absence of a welding strength difference, the welding strength of the lead terminals 16 and 17 and the 2nd laminate film 13 may be comparable as a conventional product.

  In order to make the welding strength between the lead terminals 16 and 17 and the first laminate film 12 weaker than the welding strength with the second laminate film 13, the thermal welding temperature is changed or two kinds of tab films 18 are used. The method of doing is mentioned. Specifically, for example, the welding temperature with the first laminate film 12 is made lower than the welding temperature with the second laminate film 13, or as the tab film 18 sandwiched between the first laminate film 12 side, By using a resin composed of a resin having a higher molecular weight than the resin forming the tab film 18 on the second laminate film 13 side, the weld strength with the first laminate film 12 is welded with the second laminate film 13. Can be weaker than strength.

Next, the effect of this embodiment will be described.
According to this embodiment, at least one of the positive and negative lead terminals 16 and 17 has a welding strength with the first laminate film 12 that is weaker than a welding strength with the second laminate film 13. Therefore, when the internal pressure of the battery rises due to an internal short circuit or the like, the first laminate film 12 having a low welding strength and the lead terminals 16 and 17 are peeled off from the welded portion, and the lead terminals 16 and 17 are connected to the first and second lead terminals. This prevents the welded portions of the laminate films 12 and 13 from being peeled at a time. As a result, it is possible to provide a highly safe battery that prevents the power generation element 15 from popping out.
In addition, peeling of the welding part of the 1st laminate film 12 and the lead terminals 16 and 17 is the welding part of the lead terminals 16 and 17 and the resin layer 18, and the resin layer 18 and the first laminate film 12. It occurs when at least one of the welded parts is peeled off.

<Embodiment 2>
Next, Embodiment 2 of the present invention will be described with reference to FIG.
In the present embodiment, a part of the positive electrode lead terminal 16 and the negative electrode lead terminal 17 is welded to one edge portion of the battery container 11 and led out to the outside. Other points are the same as in the first embodiment.
According to the present embodiment, the positive and negative lead terminals 16 and 17 are arranged on one edge of the battery case 11, which is suitable when it is desired to save space.

Hereinafter, the present invention will be described in more detail with reference to examples.
(1) Production of power generation element 15 The negative electrode plate was composed of 92 parts by weight of graphite as a negative electrode active material and 8 parts by weight of polyvinylidene fluoride (PVdF) as a binder on both sides of a negative electrode current collector made of copper foil having a thickness of 14 μm. The mixed negative electrode mixture was applied, pressed, and dried to form a negative electrode mixture layer. The negative electrode current collector was ultrasonically welded with a 3 mm × 40 mm × 100 μm piece of copper plated with 2 μm nickel as the negative electrode lead terminal 17.

  The positive electrode plate is composed of 91 parts by weight of lithium cobalt composite oxide as a transition metal oxide capable of occluding and releasing lithium ions and 3 acetylene black as a conductive agent on both surfaces of a positive electrode current collector made of an aluminum foil having a thickness of 20 μm. A positive electrode mixture in which 6 parts by weight of PVdF as a binder and 6 parts by weight of PVdF was mixed as a binder was applied and produced in the same manner as the negative electrode plate. An aluminum piece of 3 mm × 40 mm × 100 μm was ultrasonically welded as the positive electrode lead terminal 16 to the positive electrode current collector.

  As a separator, a polyethylene microporous film was used, and a positive electrode plate and a negative electrode plate were wound around this separator to produce a power generation element 15. The power generation element 15 had a length in the winding axis direction of 90 mm, a width of 60 mm, and a thickness of 10 mm.

(2) Production of Battery 10 As the nonaqueous electrolyte, a solution obtained by dissolving 1 mol / l of LiPF ₆ in a solvent in which ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 3: 7 was used.

  As a material for the battery container 11, a laminate film formed by dry laminating a polyethylene terephthalate (PET) film having a thickness of 12 μm, an aluminum foil having a thickness of 9 μm, and a polyethylene (PE) film having a thickness of 60 μm is used. It was.

  Two laminated films, the PE film being on the inside, the edges where the lead terminals 16 and 17 are not led out are thermally welded, the power generation element 15 is accommodated, and the positive and negative electrodes connected to the power generation element 15 Lead terminals 16 and 17 were arranged so as to be led out of the battery 10 from the opposite edge of the battery container 11 (see FIG. 1). Next, as shown in (Example 1) to (Example 4) and (Comparative Example 1), the battery 10 of Embodiment 1 shown in FIG. 1 was produced. The nominal capacity of the batteries 10 of Examples 1 to 4 and Comparative Example 1 was 4 Ah.

Example 1
The tab film 18 sandwiched between the lead terminals 16 and 17 and the two laminate films 12 and 13 is made of polyethylene having a molecular weight of 70,000, and the positive lead terminal 16 and the first laminate film 12 are 200. The positive electrode lead terminal 16 and the second laminate film 13 were heat-welded at 230 ° C.

  Thermal welding between the negative electrode lead terminal 17 and the two laminated films 12 and 13 was performed in the same manner as the positive electrode lead terminal 16.

  Next, the edge part excluding the nonaqueous electrolyte injection port was thermally welded to vacuum-inject the nonaqueous electrolyte, and then the liquid injection port was thermally welded and sealed to produce the battery 10 of Example 1. .

(Example 2)
A battery 10 of Example 2 was produced in the same manner as in Example 1 except that both the negative electrode lead terminal 17 and the first and second laminate films 12 and 13 were thermally welded at 230 ° C.

(Example 3)
The tab film 18 is made of polypropylene having a molecular weight of 70,000 and that made of polypropylene having a molecular weight of 50000, respectively, between the first laminate film 12 and the positive electrode lead terminal 16, and the second laminate film 13 and the positive electrode lead terminal 16. And heat-welded at 230 ° C.

  Thermal welding of the negative electrode lead terminal 17 and the first and second laminate films 12 and 13 was performed in the same manner as the positive electrode lead terminal.

  Next, the edge part excluding the nonaqueous electrolyte injection port was thermally welded to vacuum-inject the nonaqueous electrolyte, and then the liquid injection port was thermally welded and sealed to prepare the battery 10 of Example 3. .

Example 4
Example 3 except that the negative electrode lead terminal 17 and the first and second laminate films 12 and 13 were thermally welded at 230 ° C. using a polypropylene tab film having a molecular weight of 50000. A battery 10 of Example 4 was produced in the same manner as described above.

(Comparative Example 1)
A battery of Comparative Example 1 was produced in the same manner as in Example 1 except that thermal welding of the positive and negative electrode lead terminals 16 and 17 and the first and second laminated films 12 and 13 was performed at a welding temperature of 230 ° C. .

(3) Welding strength The portions of the batteries 10 of Examples 1 to 4 and Comparative Example 1 where the lead terminals 16 and 17 and the laminate film are thermally welded are cut out, and the first laminate film is used by using a tensile tester. The rupture strength when the 12 and the second laminate film 13 were peeled off from the lead terminals 16 and 17 was measured to obtain the welding strength.

  Table 1 shows values obtained by dividing the welding strength of the second laminate film 13 by the welding strength of the first laminate film 12. If this value is 1, it indicates that the welding is performed with the same welding strength. If the value is larger than 1, the welding strength of the first laminate film 12 is higher than the welding strength of the second laminate film 13. Indicates weakening.

(4) Safety test of battery 10 In order to confirm the safety of the battery, the battery 10 of Examples 1 to 4 and Comparative Example 1 was subjected to a nail penetration test.
The nail penetration test was carried out in accordance with Battery Industry Association Standard SBA G 1101 (“Guidelines for Safety Evaluation of Lithium Ion Secondary Batteries”). The test was performed by using a steel nail having a diameter of 5 mm, a length of 100 mm, and a tip angle of 30 °, and penetrating the battery 10 as a test object from the side of the battery case at a speed of 24 mm / sec.

<Test results and discussion>
In the batteries of Examples 1 to 4, the first laminate film 12 was peeled off from the lead terminals 16 and 17, but no white smoke or jumping out of the power generation element was observed. This is because, in the batteries of Examples 1 to 4, the welding strength with the first laminate film 12 is higher than the welding strength with the second laminate film 13 in at least one of the positive and negative lead terminals 16 and 17. Since it is weak, it is considered that the two laminated films 16, 17 may not have been peeled off at once.

  On the other hand, in the battery of Comparative Example 1, the first and second laminate films 12 and 13 were peeled from the lead terminals 16 and 17 almost simultaneously, and white smoke was seen from the peeled portions. This is presumably because in the battery of Comparative Example 1, both the positive electrode and the negative electrode lead terminal were welded with the same strength as the first and second laminate films 12 and 13.

  As described above, if at least one of the positive electrode and the negative electrode lead terminals 16 and 17 has a welding strength with the first laminate film 12 that is weaker than a welding strength with the second laminate film 13, an internal short circuit or the like. As a result, it was found that a battery with high safety capable of preventing the power generation element and the like from popping out when the internal pressure of the battery increases can be provided.

<Other embodiments>
The present invention is not limited to the embodiments described with reference to the above description and drawings. For example, the following embodiments are also included in the technical scope of the present invention.
(1) In the above embodiment, as the battery container, two laminate films were stacked and the edges were heat-welded, but one laminate film was formed into an envelope shape, One laminate film may be folded in half and three sides may be heat-welded.

  (2) Although the present invention is applied to the lithium ion secondary battery in the above embodiment, the present invention may be applied to other types of batteries, such as a nickel metal hydride battery and a nickel cadmium battery.

The perspective view of the battery of Embodiment 1. AA sectional view The perspective view of the battery of Embodiment 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Battery 11 ... Battery container 12 ... 1st laminate film 13 ... 2nd laminate film 14A ... Film layer 14B ... Barrier layer 14C ... Thermal welding layer 15 ... Electric power generation element 16 ... Positive electrode lead terminal 17 ... Negative electrode lead terminal 18 ... Tab film (resin layer)

Claims (2)

A battery in which a power generation element including a positive electrode plate and a negative electrode plate is housed in a battery container formed by stacking a first laminate film and a second laminate film and welding an edge,
A positive electrode lead terminal and a negative electrode lead terminal are connected to the positive electrode plate and the negative electrode plate,
The positive electrode lead terminal and the negative electrode lead terminal are sandwiched between the first laminate film and the second laminate film at the edge of the battery container, and a part thereof is thermally welded via a resin layer. And led out from the battery container,
At least one of the positive electrode lead terminal and the negative electrode lead terminal has a welding strength with the first laminate film that is weaker than a welding strength with the second laminate film. The weld strength with the first laminate film in the positive electrode lead terminal and the negative electrode lead terminal is weaker than the weld strength with the second laminate film. battery.

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