JP2001052681A - Polymer electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polymer electrolyte battery which is easy to align at the time of joining a lead portion of an electrode to an electrode terminal or a lead body to the electrode terminal, and has excellent productivity. A sheet-shaped positive electrode having a positive electrode active material-containing layer formed on at least one surface of a metal foil and a sheet-shaped negative electrode having a negative electrode active material-containing layer formed on at least one surface of the metal foil are provided. In a polymer electrolyte battery in which a sheet-like polymer electrolyte layer is interposed and laminated to form an electrode group, and the innermost layer is sealed with an outer package composed of a heat-sealing film, the above-mentioned positive electrode or negative electrode The width of the lead portion of one of the electrodes is made wider than the width of the electrode terminal or the lead body to the electrode terminal to constitute a polymer electrolyte battery.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte battery, and more particularly, to a method of easily positioning a lead portion of an electrode and an electrode terminal or a lead body to the electrode terminal at the time of joining, and improving productivity. It relates to an excellent polymer electrolyte battery.

[0002]

2. Description of the Related Art A characteristic of a polymer electrolyte battery is that the electrodes and the polymer electrolyte layer constituting the electrode group are formed in a thin sheet shape, and a battery which is easily thinned and has excellent flexibility can be obtained. The thin electrode of the polymer electrolyte battery is obtained by forming an active material-containing layer on at least one surface of a thin metal foil by applying and gelling an active material-containing paste, and is usually a long continuous sheet in terms of productivity. The shape is used as the source. And when incorporating it into a battery,
The electrode is formed into a desired shape by punching the above-mentioned long raw material, and in this case, the active material is punched out so as to straddle the formation portion of the active material containing layer and the portion where the active material containing layer is not formed. The narrow part where the containing layer is not formed is used as the lead part of the electrode.

However, as described above, since the lead portion of the electrode is formed of a very thin metal foil, if it is used as it is as an electrode terminal such as a positive electrode terminal or a negative electrode terminal which is an external terminal of the battery, it is difficult to use a mechanical device. Due to the low target strength, breakage is likely to occur, and practicality is lacking. for that reason,
One end of an electrode terminal separately manufactured with a metal plate thicker than the lead of the electrode is joined to the lead of the electrode, and the other end of the electrode terminal is drawn out of the battery. It is generally used for bonding.

In order to obtain a higher capacity battery in this polymer electrolyte battery, a plurality of positive electrodes and a plurality of negative electrodes are laminated with a polymer electrolyte layer interposed therebetween, and the laminated electrode group is formed. Is sealed with the same exterior material as described above to produce a laminated polymer electrolyte battery. In such a laminated polymer electrolyte battery, since the lead portion of the electrode is also plural, the lead body is interposed between the lead portion and the electrode terminal without directly joining the laminate of the lead portion and the electrode terminal. One end of the lead body is joined to the laminate of the lead portion, and the other end of the lead body is joined to one end of the electrode terminal.

[0005] By the way, the lead part of the electrode and the electrode terminal or the lead body to the electrode terminal (the lead body interposed between the lead part of the electrode and the electrode terminal as described above is called "lead body to the electrode terminal"). In order to secure the mechanical strength and to reduce the voltage drop at this portion, it is preferable that the area of the junction is large. However, if the width of the lead portion of the electrode is the same as the width of the electrode terminal or the lead body, in order to secure a desired bonding area, positioning at the time of bonding them, and control of the position at which the head of the bonding apparatus hits, are performed. It has to be performed strictly, and there is a problem that productivity is reduced.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and appropriately adjusts the relationship between the width of the electrode lead portion and the width of the electrode terminal or the lead member to the electrode terminal. Accordingly, an object of the present invention is to provide a polymer electrolyte battery which facilitates alignment at the time of joining thereof and has excellent productivity.

[0007]

SUMMARY OF THE INVENTION According to the present invention, the width of the lead portion of the electrode is made larger than the width of the electrode terminal or the lead body to the electrode terminal. The object of the present invention is to solve the above-mentioned problem by ensuring that a desired bonding area can be obtained even when the alignment with the lead body is relatively rough.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as a metal foil serving as a current collector of a positive electrode, for example, an aluminum foil, a stainless steel foil or the like is used, and an aluminum foil is particularly preferable. The thickness of the metal foil as a current collector of the positive electrode is preferably 10 to 20 μm from the viewpoint of reducing the thickness of the positive electrode and securing strength.

The lead portion of the positive electrode is usually provided by leaving the exposed portion of the metal foil without forming the positive electrode active material-containing layer on a part of the metal foil at the time of manufacturing the positive electrode.

The positive electrode terminal as the external terminal is preferably a metal foil or ribbon of nickel, nickel-plated iron, copper, stainless steel, or the like, for ease of connection with equipment using a battery. 20-300 μm,
Particularly, the thickness is preferably from 40 to 200 μm. Further, when a lead body is interposed without directly joining the positive electrode terminal and the lead portion, it is preferable that the lead body is made of aluminum, and the thickness of the lead body is
As in the case of the above-mentioned positive electrode terminal, the thickness is preferably 20 to 300 μm, particularly preferably 40 to 200 μm.

As the joining method of the lead portion of the positive electrode and the positive electrode terminal or the lead body, for example, ultrasonic welding, resistance welding, laser welding and the like are suitably adopted.

As the metal foil serving as the current collector of the negative electrode, for example, a copper foil, a nickel foil, a stainless steel foil or the like is used, and a copper foil is particularly preferable. The thickness of the metal foil serving as the current collector of the negative electrode is preferably 5 to 20 μm for the same reason as in the case of the positive electrode, and the lead portion of the negative electrode also usually has a part of the metal foil when the negative electrode is manufactured. It is provided by leaving the exposed portion of the metal foil without forming the negative electrode active material containing layer.

The negative terminal as an external terminal on the negative side includes:
Like the positive electrode terminal, a metal foil or ribbon of nickel or nickel-plated iron, copper, stainless steel or the like is preferably used, and the thickness thereof is 20 to 300 μm, particularly 40 μm, as in the case of the positive electrode terminal. ~ 200 µm is preferred. Further, when a lead body is interposed between the lead portion of the negative electrode and the negative electrode terminal, it is preferable to use a copper lead as the lead body, and the thickness of the lead body is the same as in the case of the negative electrode terminal. , 20-300μ
m, particularly preferably 40 to 200 μm.

As a method for joining the lead portion of the negative electrode and the negative electrode terminal or the lead body to the negative electrode terminal, for example, ultrasonic welding, resistance welding, laser welding, or the like is suitably employed.

In the manufacture of this type of battery, the positioning accuracy between the electrode lead portion and the electrode terminal or the lead body to the electrode terminal is usually about ± 1 mm. Therefore, the width of the lead portion of the electrode is 1 mm larger than the width of the electrode terminal or the lead body.
As long as it is wider, the positioning accuracy may be lower as the width of the lead portion is wider, but the lower positioning accuracy of the electrode lead portion leads to a positional shift between the positive electrode and the negative electrode, and as a result, The contact state between the positive electrode and the negative electrode via the polymer electrolyte layer is deteriorated, and the performance of the battery is lowered. In particular, the reduction of the capacity density (mAh / cc) becomes large. It is preferable that the width be as wide as possible as long as it is 1 mm or more from the width of the lead body and does not contact the lead portion of each electrode. However, the gap between the lead portions of each electrode may be about 2 mm. In the present invention, the width of the electrode terminal or the lead to the electrode terminal is not made wider than the width of the electrode lead, and the width of the electrode lead is made wider than the width of the electrode terminal or the lead to the electrode terminal. This is because the number of electrode terminals or the lead body to the electrode terminal is one, while the number of lead portions of the electrode is plural, so that there is much opportunity for displacement.

The positive electrode, the negative electrode, the polymer electrolyte layer and the like may be of the usual structure in this type of battery, and the exterior material is not particularly limited as long as the innermost layer is made of a heat-fusible resin. Although it is possible to use a structure similar to that of the related art, specific examples of the exterior material include, for example, a three-layer laminate film composed of a nylon film or a polyester film-aluminum film-modified polyolefin film. The above-mentioned modified polyolefin film is located at the innermost layer (this innermost layer means that it is the innermost layer at the time of use and does not mean the inner layer in the laminate film). It is configured.

The electrode is usually produced by applying an active material-containing paste to a metal foil serving as a current collector and gelling the same to form an active material-containing layer on the surface of the metal foil. The active material-containing paste and the active material-containing layer may be any as long as they contain an active material as an essential component, and may further contain a binder and, if necessary, a conductive auxiliary and a thickener. Good.

[0018]

Next, the present invention will be described specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 First, as shown in the following, a positive electrode, a negative electrode, and a polymer electrolyte layer serving as a separator were prepared.

Positive electrode: LiCoO ₂ as positive electrode active material
After dry mixing 40 parts by weight of the powder, 8 parts by weight of flake graphite powder as a conductive aid and 5 parts by weight of polyvinylidene fluoride (hereinafter abbreviated as “PVdF”) powder as a binder, 1.22 M (mol) was further added. / L) LiPF
Ethylene carbonate / propylene carbonate containing ₆ (hereinafter "EC / PC" abbreviated) (50/50) solution 25 parts by weight of the added active substance-containing paste prepared by mixing, thickness 20μm as a collector Is applied to both sides of the aluminum foil to a thickness of 75 μm, and then heated at 120 ° C. for 20 minutes to form a positive electrode active material-containing layer on both sides of the aluminum foil (PVdF is melted by the above heating, and the temperature is lowered). When the PVdF decreases, the PVdF gels, and at that time, the whole is taken into PVdF, including the solvent, and becomes non-fluidized to form a flexible positive electrode active material-containing layer), thereby producing a sheet-shaped positive electrode. This positive electrode is a so-called double-sided coated positive electrode. Separately from this, as a positive electrode to be disposed on the outermost layer of the laminated electrode group, the above-mentioned positive electrode active material-containing paste is applied to one surface of an aluminum foil, and heated in the same manner as above to form a current collector. By forming a positive electrode active material-containing layer only on one side of the above, a so-called one-side coated positive electrode was also prepared. In each case, however, the positive electrode active material-containing paste was not applied to the portion to be the lead portion, and the aluminum foil was exposed. E above
C / PC (50/50) is ethylene carbonate (E
This indicates that the mixed solvent has a ratio of C) to propylene carbonate (PC) of 50:50 by volume.

Negative electrode: 40 parts by weight of spheroidal graphite powder, 4 parts by weight of flaky graphite powder and 5 parts by weight of PVdF powder are mixed in a dry system, and then EC containing 1.22 M of LiPF ₆ is further added.
The negative electrode active material-containing paste prepared by adding and mixing 5 parts by weight of a / PC (50/50) solution is mixed with a current collector having a thickness of 2
After coating on both surfaces of a 0 μm copper foil to a thickness of 75 μm, respectively, and heating at 120 ° C. for 20 minutes to form a negative electrode active material-containing layer on both surfaces of the copper foil, a sheet-like so-called double-sided coated negative electrode is produced. did. Also, as in the case of the positive electrode,
As a negative electrode to be arranged on the outermost layer of the stacked electrode group, the paste containing the negative electrode active material is applied to one surface of a copper foil, and heated in the same manner as above to form a negative electrode active material on only one surface of the copper foil serving as a current collector. By forming the containing layer, a so-called single-sided coated negative electrode was produced. However, in any of the negative electrodes, the active material-containing paste was not applied to the portion to be the lead portion, and the copper foil was exposed.

Polymer electrolyte layer: After mixing 50 parts by weight of 2-ethoxyethyl acrylate, 13 parts by weight of triethylene glycol dimethacrylate and 33 parts by weight of ethylene glycol ethyl carbonate methacrylate, 5 parts by weight of benzoyl peroxide and 1.22 M
EC / PC (50/50) solution 35 containing LiPF ₆
After the benzoyl peroxide was completely dissolved, a polybutylene terephthalate nonwoven fabric having a thickness of 60 μm and a basis weight of 30 g / m ² was immersed therein. After the solution completely infiltrates the nonwoven fabric, the immersed nonwoven fabric is 75μ
sandwiched between two glass plates having a gap of
It heated at 20 degreeC for 20 minutes, and produced the sheet-shaped polymer electrolyte layer.

As the positive electrode, three double-coated positive electrodes were used, one single-coated positive electrode was used, and three double-coated negative electrodes were used as the negative electrode.
One single-sided negative electrode was used, and the polymer electrolyte layer was 7
Using the positive electrode, the negative electrode, the polymer electrolyte layer,
A negative electrode, a polymer electrolyte layer, a positive electrode,..., A negative electrode, a polymer electrolyte layer, and a positive electrode were sequentially laminated with four positive electrodes, four negative electrodes, and seven polymer electrolyte layers to prepare a laminated electrode group.

FIG. 1 schematically shows a plan view of the above-mentioned laminated electrode group and members associated therewith. FIG. 2 schematically shows a cross-sectional view of a connection portion between the lead portion of the positive electrode of the polymer electrolyte battery of Example 1 and the lead body to the positive electrode terminal and the vicinity thereof. The laminated electrode group is composed of four positive electrodes, seven polymer electrolyte layers and four negative electrodes. As shown in FIG. A part of the negative electrode 2 (lead part 2c of the negative electrode 2) is described below. The positive electrode 1, the negative electrode 2, and the polymer electrolyte layer 3 will be described below with reference to FIG. In FIG. 1, a part of the exterior material 4 is shown by a dashed line in order to clarify the positional relationship between the stacked electrode group and the exterior material.

The positive electrode 1 is at the uppermost portion and is shown with a dot, under which the polymer electrolyte layer 3 is arranged, and further below this, the negative electrode 2 is arranged. The area of the negative electrode 2 is larger than that of the positive electrode 1, the area of the polymer electrolyte layer 3 is larger than that of the negative electrode 2, and the polymer electrolyte layer 3 also has a function of separating the positive electrode 1 from the negative electrode 2.

The lead portion 1c of the positive electrode 1 is constituted by an exposed portion of an aluminum foil which is a current collector of the positive electrode 1, and has a width of 8 m.
m, the length is 9 mm, and four positive electrodes 1 are used. Thus, as shown in FIG. 2, the lead body 1c is formed into a four-layered body at the time of joining with the lead body.

The lead member 7 connects the lead portion 1a and the positive electrode terminal 5 and is made of an aluminum ribbon having a thickness of 100 μm, and has a width of 5 mm and a length of 7.5.
mm, and the width of the lead portion 1c is 8 mm as described above, so that the width of the lead portion 1c is 3 mm wider than the width of the lead body 7, and one end of the lead body 7 is And the other end of the lead body 7 is joined to one end of the positive electrode terminal 5 by ultrasonic welding.

The positive electrode terminal 5 is formed of a nickel ribbon having a thickness of 40 μm, and one end of the positive electrode terminal 5 is joined to the end of the aluminum lead body 7 at the sealing portion 4a of the exterior material 4 by ultrasonic welding. The other end is exterior material 4
Is drawn out from the seal portion 4a of the battery pack and is used as a so-called external terminal for connection with a battery-using device.
Although not shown, the positive electrode terminal 5 and the lead 7
It is preferable to wrap an insulating tape such as a polyimide tape around the joint with the above so that short circuit due to burrs does not occur.

The exterior material 4 is composed of a laminate film having a three-layer structure of a nylon film-aluminum film-modified polyolefin film, two of which are used, one of which is in a container shape for accommodating the above-mentioned laminated electrode group. And the other serves as its sealing lid.

The joining of the positive electrode terminal 5 and the lead body 7 is performed at the sealing portion 4a of the two exterior members 4, and the sealing portion 4a is not shown in FIG. As shown in FIG. 2, a sealing material 9 is provided,
Thereby, the inside of the battery is sealed. In other words, at the sealing portion 4a of the exterior material 4 where the junction with the positive electrode terminal 5 and the lead body 7 does not intervene, the inside of the battery can be sealed by heat fusion between the modified polyolefin films of the exterior material 4, In the portion where the junction between the positive electrode terminal 5 and the lead body 7 is interposed, a gap is easily generated only by heat-sealing the modified polyolefin film of the exterior material 4. It is to be able to secure sealing. As the sealing material 9, a heat-fusible resin such as an ionomer is preferably used.

As described above, the joint between the positive electrode terminal 5 and the lead body 7 is arranged at the sealing portion 4a of the exterior material 4a because nickel and aluminum have an electrolyte interposed between them. Then, a local battery is formed to cause corrosion of aluminum, so that no electrolytic solution is interposed between the positive electrode terminal 5 made of nickel and the lead body 7 made of aluminum.

That is, the positive electrode terminal 5 is made of nickel for the convenience of joining with a battery device by soldering or the like. Aluminum is used for the metal foil serving as the current collector of the positive electrode 1, and the lead portion of the positive electrode 1 is used. 1c, since the lead body 7 is also made of aluminum, in order to avoid the corrosion of aluminum due to the formation of a local battery, the joint between the positive electrode terminal 5 and the lead body 7 should be joined at a position not exposed to the electrolytic solution. It is desirable to keep it.

The lead portion 2c of the negative electrode 2 is constituted by an exposed portion of a copper foil, which is a current collector of the negative electrode 2, and has a width of 9 mm and a length of 7.5 mm. Although not shown, the lead portion 2c is formed into four laminated bodies when joining with the lead body 8.

The negative electrode-side lead body 8 connects the negative electrode lead portion 2c and the negative electrode terminal 6, and has a thickness of 40 μm.
m, a width of 5 mm, a length of 7.5 mm, and a width of the lead portion 2 c of 9 mm as described above.
mm, the width of the lead portion 2c is 4 mm wider than the width of the lead member 8. One end of the lead member 8 is joined to the laminate of the lead portion 2c of the negative electrode 2 by ultrasonic welding. The other end of the lead body 8 is joined to one end of the negative electrode terminal 6 by ultrasonic welding.

FIG. 3 is a cross-sectional view schematically showing the polymer electrolyte battery according to the first embodiment. The stacked electrode group is formed by using four positive electrodes 1, four negative electrodes 2, and seven polymer electrolyte layers 3. The polymer electrolyte battery is constituted by sealing the laminated electrode group with an exterior material 4 composed of a three-layer laminated film of a nylon film-aluminum film-modified polyolefin film. However, in FIG. 3, the drawing direction of the negative electrode terminal 6 is different from that in FIG. That is, in this type of polymer electrolyte battery, the positive electrode terminal 5 and the negative electrode terminal 6 are usually drawn in the same direction while providing a space necessary for preventing short circuit between them as shown in FIG. In order to faithfully illustrate this, the negative terminal 6 is connected to the positive terminal 5.
3, the drawing direction of the negative electrode terminal 6 is changed by 180 ° in FIG.
The battery is illustrated as if the positive terminal 5 and the negative terminal 6 were pulled out in opposite directions.

The above-mentioned laminated electrode group corresponds to a structure in which four unit cells each composed of the positive electrode 1, the polymer electrolyte layer 3 and the negative electrode 2 are laminated. One of the inner unit cells is taken out, and the main part thereof is shown in FIG.

Since this unit cell is located inside the laminated electrode group, a so-called double-sided coated electrode is used for both the positive electrode 1 and the negative electrode 2. As shown in FIG. It is constituted by forming a positive electrode active material-containing layer 1b on both sides of a foil (the aluminum foil in this example 1) 1a, and a portion of the aluminum foil where the positive electrode active material-containing layer is not formed is a lead portion. 1c. The negative electrode 2 is formed by forming a negative electrode active material-containing layer 2b on both surfaces of a metal foil (a copper foil in the first embodiment) serving as a current collector. The portion where the containing layer is not formed is the lead portion 2
c.

It should be noted that FIGS. 1 to 4 are all schematic diagrams, and the dimensions and ratios of the respective components are not always accurate except for specific ones.

Comparative Example 1 The width of the lead portion of the positive electrode was set to 5 mm, and the width of the lead portion of the negative electrode was set to 5 mm (that is, the width of the lead portion of the positive electrode was equal to the width of the lead body on the positive electrode side). , And the width of the lead portion of the negative electrode and the width of the lead body on the negative electrode side were the same, except that the polymer electrolyte battery was manufactured in the same manner as in Example 1.

Table 1 shows the results of manufacturing 100 batteries each of the above-mentioned Example 1 and Comparative Example 1 and examining the yield. The production of the battery of Example 1 and the battery of Comparative Example 1 were performed online at the same speed, and the determination of non-defective and defective products on which the yield was calculated was based on the lead portion of the electrode and its lead body. Was observed by a microscope.

[0041]

[Table 1]

As shown in Table 1, the battery of Example 1 had higher yield and higher productivity than the battery of Comparative Example 1.

In preparing the polymer electrolyte layer, in addition to the case described in the above embodiment, for example, a polymer gelled, a radical polymerizable unsaturated polyester, or a radical polymerizable acrylic epoxy may be used. Alternatively, a photocurable resin such as acrylate, urethane acrylate, polyester acrylate, alkyd acrylate, or silicon acrylate that is polymerized using ultraviolet light or an electron beam to gel the electrolyte may be used.

[0044]

As described above, according to the present invention, it is possible to provide a polymer electrolyte battery which facilitates the alignment of the lead portion of the electrode and the electrode terminal or the lead body to the electrode terminal, and has high productivity. We were able to.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a stacked electrode group and its vicinity in a polymer electrolyte battery according to Example 1 of the present invention.

FIG. 2 is a cross-sectional view schematically showing a connecting portion of a lead body of a positive electrode and a lead body to a positive electrode terminal and the vicinity thereof in a polymer electrolyte battery according to Example 1 of the present invention.

FIG. 3 is a cross-sectional view schematically showing a polymer electrolyte battery according to Example 1 of the present invention.

FIG. 4 is a cross-sectional view schematically illustrating a main part of one unit cell taken out of the stacked electrode group used in the polymer electrolyte battery according to the first embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Metal foil 1b Positive electrode active material containing layer 1c Lead part 2 Negative electrode 2a Metal foil 2b Negative electrode active material containing layer 2c Lead part 3 Polymer electrolyte layer 4 Exterior material 4a Sealing part 5 Positive electrode terminal 6 Negative electrode terminal 7 Lead member on the positive electrode side 8 Lead body on negative electrode side 9 Sealing material

Claims (3)

[Claims] 1. A sheet-shaped positive electrode having a positive electrode active material-containing layer formed on at least one surface of a metal foil and a sheet-shaped negative electrode having a negative electrode active material-containing layer formed on at least one surface of the metal foil. And a laminate in which a sheet-shaped polymer electrolyte layer is interposed between the electrode group and the electrode group, and the above-described positive electrode or negative electrode in the polymer electrolyte battery in which this electrode group is sealed with an outer package in which the innermost layer is formed of a heat sealing film. Wherein the width of the lead of one of the electrodes is wider than the width of the electrode terminal or the lead to the electrode terminal. 2. The lead of the positive electrode is wider than the width of the lead to the positive terminal or the positive terminal, and the width of the lead of the negative electrode is wider than the width of the lead to the negative terminal or the negative terminal. Polymer electrolyte battery. 3. A stacked electrode group comprising a plurality of positive electrodes and a plurality of negative electrodes, each of which has a plurality of positive electrodes and a plurality of negative electrodes stacked therebetween with a polymer electrolyte layer interposed therebetween. The polymer electrolyte battery according to the above.