JP2005222872A - Laminated battery - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated battery in which the gas generated inside the battery can be exhausted certainly from a gas exhaust part established beforehand. <P>SOLUTION: This is the laminated battery 1 which comprises an electrode body 11, both electrode terminals 12, 13 connected to the electrode body 11, and a laminate film 14 enveloping the electrode body 11, and in which the edge side of the laminate film 14 is fused to form a fused part and a gas exhaust part is installed at a part of the fused part, and the both electrode terminals 12, 13 protrude from the fused part. The battery 1 has a guide 15 which is arranged in the surrounding of the electrode body 11 and forms a gas passage connected to the gas exhaust part between the edge side of the electrode body 11. The guide 15 is enveloped by the laminate film 14 together with the electrode body 11. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a laminate battery inserted into a laminate outer package. More specifically, the present invention relates to a laminate battery in which an electrode body of a secondary battery such as a lithium battery is inserted into a laminate outer package and its outer periphery is welded.

  Conventionally, a thin and lightweight secondary battery welded and sealed using a laminate film as an exterior body has been used. In this secondary battery, when an abnormality such as overcharge or short circuit occurs, a large amount of gas is generated inside and the internal pressure may increase. Also, the internal pressure may increase due to a large change in the operating environment temperature. Since the laminate film itself is not high in strength, it has been devised in consideration of safety (for example, see Patent Document 1 and Patent Document 2). In the battery described in Patent Document 1, a safety valve mechanism including a through hole and a valve plate is provided on one side wall. In the battery described in Patent Document 2, a reinforcing member is provided between the laminate outer package and the electrode assembly.

In general, the laminate battery is provided with a gas discharge portion for discharging generated gas when an abnormality occurs in order to prevent the internal pressure from increasing excessively despite such a safety mechanism. This is, for example, a part where the surrounding welding is intentionally weakened, and when the internal pressure rises too much, this part is peeled off to release the gas to the outside. Since this generated gas may be harmful to the human body or other devices, an exhaust duct or the like is provided in correspondence with the gas discharge part to guide the gas to a safe position. This prevents the exhaust gas from flowing into other parts.
JP-A-6-223796 (page 4-5) JP 2001-283798 A (page 3)

  However, the laminate battery has a problem in that gas may be discharged from a place other than a preset gas discharge portion. A laminate film used for such a battery has a thickness of about 100 μm, and a metal foil portion of which is often about 50 μm. Such a film has the advantage that the degree of freedom in shape is large and lightweight, but there is also a problem that it is easily deformed. In particular, it easily deforms when a force is applied during battery production, battery assembly, or use. In such a deformed portion, the strength may be reduced due to fatigue or stress corrosion, and therefore, a lower strength portion may be formed in addition to the planned gas discharge portion. In general, the welding strength varies widely, and there may be a portion where welding is weak in addition to the portion set as the gas discharge portion. For these reasons, when the part other than the gas discharge part becomes weakest, the part may be damaged when the internal pressure rises during an abnormality. Furthermore, there is a problem that gas may flow out to an unintended direction.

  The present invention has been made to solve the problems of the conventional laminate battery described above. That is, an object of the present invention is to provide a laminated battery in which gas generated inside the battery is surely discharged from a preset gas discharge portion.

  The laminate battery of the present invention, which has been made for the purpose of solving this problem, has a power generation element, an electrode connected to the power generation element, and a laminate film that wraps the power generation element. A laminated battery in which a gas discharge part is provided in a part of the welded part and an electrode protrudes from the welded part, and is disposed around the power generating element and between the edges of the power generating element, It has a guide member that forms a gas flow path connected to the gas discharge part, and the guide member is wrapped with a laminate film together with the power generation element.

  In the laminated battery of the present invention, the laminated film encloses the power generation element and the edge thereof is welded, and a gas discharge part is provided in a part of the welded part. Furthermore, in this invention, since it has the guide member arrange | positioned around the power generation element and wrapped in the laminate film, the pressure of the gas discharged | emitted from the power generation element is received by the guide member. Furthermore, since the gas flow path connected to the gas discharge section is formed between the guide member and the edge of the power generation element, the exhaust gas is guided to the gas discharge section through the gas flow path. Therefore, the laminated battery is configured such that the gas generated inside the battery is reliably discharged from a preset gas discharge portion.

Furthermore, in the present invention, it is desirable that the guide member is provided over the entire circumference around the power generation element except for the gas discharge portion.
If it does in this way, a guide member can receive a pressure in the perimeter other than a gas discharge part. On the other hand, since the guide member is not provided in the gas discharge portion, the pressure of the gas guided to the gas discharge portion is not received by the guide. Therefore, in the gas discharge part, pressure is received by the welding part, and this part is destroyed first, so that it becomes a gas discharge path.

Further, in the present invention, the guide member has a gas flow path portion that opens toward the power generation element and a back portion outside the gas flow passage portion, and the laminated film is also welded to the back portion of the guide member. desirable.
In this way, the guide member is welded and fixed to the laminate film by the back portion. Therefore, there is no risk of moving inside the laminate film or scratching the power generating element. Further, since there is almost no space between the back portion of the guide member and the laminate film, the gas hardly wraps around the back portion of the guide member, and the outside of the guide member does not become a gas flow path.

Furthermore, in the present invention, the guide member is preferably a member having higher rigidity than the laminate film.
By doing so, the guide member is not broken prior to the laminate film, so that pressure can be applied.

  According to the laminate battery of the present invention, the gas generated inside the battery can be reliably discharged from a preset gas discharge portion.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the best mode for embodying the present invention will be described in detail with reference to the accompanying drawings. This embodiment is a laminate battery in which a secondary battery such as a lithium battery is enclosed in a laminate film.

  As shown in FIG. 1, the laminate battery 1 of this embodiment includes an electrode body 11 and bipolar terminals 12 and 13 protruding from the electrode body 11, and these are wrapped in a laminate film 14. The electrode body 11 is wound in a flat shape by sandwiching a separator between bipolar sheets, and corresponds to a power generation element. Bipolar terminals 12 and 13 are connected to the bipolar sheets of the electrode body 11, respectively. Further, the bipolar terminals 12 and 13 also protrude from the laminate film 14. The laminate film 14 has a metal foil coated with resin on both sides, and the periphery is sealed by heat welding. These configurations are common for laminated batteries.

  The laminate battery 1 of the present embodiment further includes a guide 15 surrounding the electrode body 11 and is sealed with a laminate film 14 together with the electrode body 11. The guide 15 has a substantially rectangular frame shape, and is formed in a Y-shaped cross section that opens toward the inner circumferential direction as shown in FIG. 2 is a cross-sectional view taken along the line AA in FIG. As shown in these drawings, the guide 15 has a gas flow path portion 15 a that opens toward the electrode body 11 and a back portion 15 b outside thereof. The guide 15 is made of a resin having high strength such as polypropylene (PP), and is formed of a material that is very thick compared to the laminate film 14. Therefore, the guide 15 is a member having higher rigidity than the laminate film 14.

  The inner circumference of the gas flow path portion 15a of the guide 15 is slightly larger than the outer circumference of the electrode body 11, and is set so that the guide 15 and the electrode body 11 are not in close contact with each other in a sealed state. Therefore, when gas is generated from the electrode body 11, this gap becomes a gas flow path. Further, the back portion 15b of the guide 15 is sandwiched between the laminate films 14 and welded together. As a result, the guide 15 is fixed and does not move inside the laminate film 14. Furthermore, this welding almost eliminates the gap on the outer peripheral side of the guide 15. Therefore, the gas flow path is only on the inner peripheral side of the guide 15, and the outer peripheral side is not a gas flow path.

  Further, as shown in FIG. 1, the guide 15 is provided with a discharge opening 21 cut out in a trapezoidal shape that becomes narrower toward the outer periphery at a part of the upper side in the drawing. Further, as shown in FIGS. 3 and 4, notches 22 and 22 with one Y-shaped piece missing are formed in the portion of the guide 15 corresponding to the positions of the bipolar terminals 12 and 13. 4 is a cross-sectional view taken along line BB in FIG. When the laminated battery 1 is manufactured, the electrode body 11 having the bipolar terminals 12 and 13 is stacked on the front side of the guide 15 in FIG. As a result, the bipolar terminals 12 and 13 are overlapped with the back portion 15b of the notch portion 22 and are extended outward. That is, the guide 15 is provided over the entire circumference around the electrode body 11 except for the discharge opening 21.

Alternatively, the configuration for passing the bipolar terminals 12 and 13 from the guide 15 to the outside may be other.
For example, as shown in FIG. 5, it is good also as a 3 piece structure. That is, gaps 23 and 23 corresponding to the widths of the bipolar terminals 12 and 13 are provided. In this case, each piece of the guide 15 can be arranged around the electrode body 11 so that the bipolar terminals 12 and 13 come to the position of the gap 23.
Alternatively, as shown in FIG. 6 and FIG. 7 which is a CC cross section thereof, the through holes 24 and 24 may be provided in the Y-shaped branch portions at positions corresponding to the positions of the bipolar terminals 12 and 13. In this case, the bipolar terminals 12 and 13 can be brought out to the outside by their tip portions passing through these through holes 24 and 24.

  In this laminated battery 1, the guide 15 and the electrode body 11 are combined in this way, and the periphery is welded by sandwiching the laminated film 14 from both sides. At this time, since the back portion 15b of the guide 15 is also welded together with the laminate film 14, the welding range is a welding portion 16 indicated by hatching in FIG. At this time, a weak weld portion 17 having a low welding strength may be provided outside the discharge opening 21 due to the welding width, the welding temperature, or the like. Alternatively, the portion may not be welded.

  In the laminated battery 1 manufactured in this way, when gas is generated inside the electrode body 11 due to an abnormality such as overcharge or short circuit, the internal pressure increases due to the gas, and the laminate film 14 expands. Here, since the guide 15 is inserted in the laminated battery 1 of this embodiment, the internal pressure is received by the guide 15. Therefore, a large force is not directly applied to the welded portion 16 at a portion where the guide 15 is present. On the other hand, in the portion where the guide 15 is not provided, that is, the portion of the discharge opening 21, the internal pressure due to the gas is directly applied to the welded portion (for example, the weak welded portion 17) of the laminate film 14. Therefore, when the internal pressure becomes very large and cannot be dealt with only by the deformation of the laminate film 14, the weakly welded portion 17 is first destroyed, and gas is discharged therefrom.

  Further, since a slight gap is provided between the guide 15 and the electrode body 11, the gas generated in the electrode body 11 is easily guided through the gap, and is broken from the weak welded portion 17 to the outside. Is discharged. That is, this gap acts as a gas flow path. Further, since there is no gap on the outer peripheral side of the guide 15, only the gap between the guide 15 and the electrode body 11 acts as a gas flow path. In view of this, an outer portion of the discharge opening 21 (for example, the weak welded portion 17) may be used as a gas discharge portion in advance, and an exhaust facility such as a duct may be provided near the outside. In general, when the laminate battery 1 is used, the upper portion in FIG. 1 is arranged vertically upward, so that the gas generated inside the laminate battery 1 is smoothly discharged from the weak welded portion 17 and processed safely. Further, when the laminated battery 1 is manufactured, the discharge opening 21 serves as an electrolyte injection port.

  As described above in detail, according to the laminated battery 1 of the present embodiment, the guide 15 is provided around the electrode body 11, so that stress load on the welded portion can be prevented, and the discharge opening 21 is provided in the guide 15. Since it is formed, the outside of the discharge opening 21 can be surely made the weakest part. Therefore, if the outside of the discharge opening 21 is set in advance as a gas discharge portion, the generated gas can be accurately guided to the gas discharge portion. Furthermore, if the welding outside the discharge opening 21 is weakened, a more reliable gas discharge portion can be obtained. Therefore, the laminated battery 1 is configured such that the gas generated inside the battery is reliably discharged from a preset gas discharge portion.

  Next, examples in which the present invention is implemented will be described. The laminate battery 1 of the example was manufactured according to the following procedure, and an overcharge test was performed together with a comparative example manufactured separately. A manufacturing procedure of the laminated battery 1 of the present invention will be described.

First, as a positive electrode material, LiMnO ₂ and 5 wt% carbon powder were mixed with normal-2-pyrrolidone (NMP), and then ₂ wt% of polyvinylidene fluoride (PVdF) was added to LiMnO ₂ to produce a positive electrode paste. did. This positive electrode paste was applied onto an aluminum foil having a thickness of 10 μm and dried to produce a positive electrode.

  Next, as a negative electrode material, carbon powder was mixed with NMP, and 2 wt% of PVdF was added to prepare a negative electrode paste. This negative electrode paste was applied onto a copper foil having a thickness of 10 μm and dried to produce a negative electrode.

A porous polyethylene separator having a thickness of 25 μm was sandwiched between the positive electrode and the negative electrode, and wound into a flat shape to produce an electrode body 11.
Next, the bipolar terminals 12 and 13 were joined to the positive electrode and the negative electrode of the electrode body 11 by ultrasonic welding, respectively.

Next, a PP guide 15 was disposed around the electrode body 11. Here, the guide 15 of the type formed in 3 pieces shown in FIG. 5 was used.
Then, these are wrapped from both sides by a laminate film 14 having a laminated structure of an Al layer 40 μm, a weld layer (PP) 50 μm, and a surface layer (PET) 30 μm, and the upper side (discharge opening 21 of the guide 15 is formed by a heat welder. The three sides except for the side where is provided are thermally welded.

Further, the electrode body 11 was impregnated with an ethylene carbonate / diethyl carbonate electrolytic solution (ratio 1: 1) added with 1 mol% of LiPF ₆ as a salt. Thereafter, the upper side of the laminate film 14 was thermally welded to complete the laminate battery 1. At this time, the thermal welding at the position corresponding to the gas discharge portion (weak welding portion 17) was slightly weaker than the other portions.

  As a comparative example, the same battery was manufactured except that the guide 15 was not provided. In the comparative example, the welding in the same position range was slightly weakened.

Ten examples of each of these examples and comparative examples were manufactured, and overcharge tests were performed on all of them under the same conditions, and the locations where the generated gas was discharged were examined. In the embodiment of the present invention, all 10 cases were discharged from the scheduled gas discharge portion (outside the discharge opening 21).
On the other hand, in the comparative example, only 4 cases out of 10 cases were discharged from the scheduled gas discharge section. In the other five cases, the welded portion other than the gas discharge portion was peeled off and discharged, and in one example, the laminate film 14 itself was broken and discharged.
Therefore, according to the laminated battery 1 of the present invention, it can be said that the gas generated inside the battery is discharged from a preset gas discharge portion.

In addition, this form is only a mere illustration and does not limit this invention at all. Therefore, the present invention can naturally be improved and modified in various ways without departing from the gist thereof.
For example, the cross-sectional shape of the guide 15 is not limited to the Y shape, and may be a U shape + leg shape or a semicircle + leg shape. Further, the leg portion does not necessarily have to be on the entire circumference.
For example, it is more preferable if the corners of the guide 15 are formed round.
Further, for example, the discharge opening 21 is not necessarily an oblique opening. It is good also as an opening of the same width as a whole. Further, the arrangement of the discharge opening 21 is not limited to this, but in general, the upper position during use is desirable.
For example, the positions and shapes of the bipolar terminals 12 and 13 are not limited to this. Corresponding to the arrangement of the bipolar terminals 12 and 13, the gap 22, the notch 23, the through hole 24, etc. of the guide 15 may be set.

  Further, for example, in this embodiment, the configuration corresponding to the gas discharge portion is formed by the weak weld portion 17 which is slightly weaker than the other portions, but the weak weld portion 17 is not necessarily formed. Since the pressure of the gas generated inside the battery is concentrated in the discharge opening 21 simply by providing the guide 15, even if the gas discharge portion is formed in a welded state equivalent to other portions, the gas discharge portion is reliably broken. Gas can be discharged outside the battery. In this case, the process for forming the weak welded portion 17 can be reduced.

It is a front view which shows the outline of the laminated battery which concerns on this form. It is sectional drawing which shows the outline of a laminated battery. It is a front view which shows the guide inserted in a laminate battery. It is sectional drawing which shows a guide. It is a front view which shows the guide inserted in a laminate battery. It is a front view which shows the guide inserted in a laminate battery. It is sectional drawing which shows a guide. It is explanatory drawing which shows the welding part of a laminate battery.

Explanation of symbols

1 Laminated battery 11 Electrode body (power generation element)
12, 13 Bipolar terminal (electrode)
14 Laminate film 15 Guide (guide member)
15a Gas flow path part 15b Back part 16 Welding part 17 Welding part (gas discharge part)

Claims (4)

A power generation element; an electrode connected to the power generation element; and a laminate film that wraps the power generation element. An edge portion of the laminate film is welded to form a welded portion, and gas is discharged to a part of the welded portion. In a laminated battery in which a part is provided and the electrode protrudes from the weld part,
A guide member that is disposed around the power generation element and that forms a gas flow path connected to the gas discharge portion between the power generation element and an edge thereof;
The laminated battery, wherein the guide member is wrapped in the laminated film together with the power generation element. The laminated battery according to claim 1,
The laminated battery according to claim 1, wherein the guide member is provided over the entire periphery of the power generation element except for the location of the gas discharge portion. In the laminate battery according to claim 1 or 2,
The guide member has a gas flow path portion that opens toward the power generation element, and a back portion on the outside thereof,
In the welding portion, the laminated film is also welded to the back portion of the guide member. In the laminate battery according to any one of claims 1 to 3,
The laminated battery according to claim 1, wherein the guide member is a member having higher rigidity than the laminated film.

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