JP2000231914A - Layered polymer electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a layered polymer electrolyte battery with high sealability of a case sealed part, excellent storage characteristics, and highly reliable battery performance. SOLUTION: In this layered polymer electrolyte battery wherein a plurality of positive electrodes are formed by applying a positive electrode mixture layer on at least one face of an aluminum collector, a plurality of negative electrodes are formed by applying a negative electrode mixture layer on at least one face of a copper collector, a polymer electrolyte layer is interposed between respective position and negative electrodes and laminated to be a laminated electrode, and the laminated electrodes are housed in a case 4, a lead part C the same material as the collector of at least one of the positive and negative electrodes is connected to a connecting metal plate 7 the same material as the lead part C, and the connecting metal plate 7 is connected to an external terminal of the material different from the lead part of the electrodes at a sealed part 4a of the case 4 to constitute the layered 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 stacked polymer electrolyte battery, and more particularly, to a stacked polymer electrolyte battery suitable for use as a power source for portable electronic devices, electric vehicles, road leveling, and the like.

[0002]

2. Description of the Related Art In a polymer electrolyte battery, the electrolyte can be made into a sheet shape, thereby making it possible to produce a large-area and thin battery such as an A4 size plate or a B5 size plate.
Application to various thin products has become possible, and the range of use of batteries has been greatly expanded. Batteries using this polymer electrolyte have excellent safety and storage properties including leakage resistance,
Moreover, because it is thin and flexible, it has the unique feature of batteries that can be designed to match the shape of the device.

[0003] This polymer electrolyte battery usually uses a laminate film in which an aluminum film is used as a core material and a resin film serving as an adhesive layer is provided on the inner surface side for an outer package, and a thin sheet-like electrode and a sheet-like polymer electrolyte layer are used. By packaging the unit cell with the above-mentioned package with the above package, a thin sheet-type battery is completed.

However, some devices using batteries require high capacity and high voltage. In such a case, a plurality of unit cells comprising the positive electrode, the negative electrode and the polymer electrolyte layer are laminated to form a laminated electrode. A group is prepared, and a plurality of positive electrodes and a plurality of negative electrodes are connected in parallel to increase the capacity, or connected in series to increase the voltage of a stacked polymer electrolyte battery.

[0005]

By the way, in a polymer electrolyte battery, even in the case of a stacked battery in which a plurality of unit cells are stacked as described above, usually, a metal foil is used as a current collector in order to make each electrode thin. The current collector of the positive electrode is made of aluminum foil, and the current collector of the negative electrode is made of copper foil. And, as the external terminal of the battery, that is, the positive terminal and the negative terminal used for connection with the battery-powered device, the ease of soldering for connection with the battery-powered device, the mechanical strength, the corrosion resistance, etc., are usually used. A nickel foil or ribbon is used.

The connection between these electrodes and external terminals is usually
During the production of the positive electrode, the exposed portion of the aluminum foil is left without forming a positive electrode mixture layer on a part of the aluminum foil, and the exposed portion is used as a lead portion to be a connection portion with a positive terminal as an external terminal. An exposed portion of the copper foil is left without forming a negative electrode mixture layer on a part of the copper foil, and this is used as a lead portion to be a connection portion with a negative electrode terminal as an external terminal.

However, if an electrolytic solution from the inside of the electrode adheres or moisture invades from the outside of the battery adheres to the connection between the lead portion of the electrode and the external terminal, a local battery is formed. There is a problem in that the connection part dissolves, lowering the battery performance, and further progressing causes so-called disconnection. And such a problem occurs remarkably especially when a battery is stored.

For this reason, it has been proposed to prevent the formation of a local battery by connecting the lead portion of the electrode and the external terminal at the sealing portion of the exterior body. Due to the use of a plurality of leads, there are also a plurality of lead portions of these electrodes, and when connecting the plurality of lead portions and the external terminals, the thickness of the connection portion increases, and the connection is performed at the sealing portion of the outer body. In this case, the adhesive resin of the exterior body does not sufficiently spread around the periphery, and the hermeticity is reduced, and the electrolytic solution adheres to the connection portion between the lead portion of the electrode and the external terminal or enters from the outside of the battery. It was not possible to solve the problem that the coming moisture adhered to form a local battery, which caused a decrease in battery performance and disconnection.

The present invention solves the above-mentioned problems of the prior art, improves the hermeticity of the sealing portion of the exterior body, prevents the formation of a local battery, has excellent storage characteristics, and has high reliability of battery performance. It is an object of the present invention to provide a laminated polymer electrolyte battery having a high level.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a plurality of positive electrodes formed by forming a positive electrode mixture layer on at least one surface of an aluminum current collector and at least one surface of a copper current collector. A plurality of negative electrodes formed of a negative electrode mixture layer, and a laminated polymer electrolyte battery in which a laminated electrode group laminated with a polymer electrolyte layer interposed between each of the positive electrode and the negative electrode is packaged with a package, The current collector of at least one of the positive electrode and the negative electrode is connected to a lead made of the same material with a metal plate for connection made of the same material as the lead, and the metal plate for connection and the lead of the electrode are made of a material By connecting different external terminals with the sealing part of the exterior body,
The present invention has solved the above problem.

That is, with the above configuration,
After connecting the lead portions of a plurality of electrodes and the metal plate for connection first, and then connecting one metal plate for connection and the external terminal with the sealing portion of the exterior body, sufficient sealing performance is obtained. It can be ensured and the formation of a local battery is prevented, thereby preventing battery performance degradation and disconnection.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, an aluminum foil, a punched metal, a net, an expanded metal and the like can be used as a current collector of a positive electrode, and an aluminum foil is usually used. The current collector of the positive electrode preferably has a thickness of 20 μm or less in view of reducing the thickness of the positive electrode,
In the present invention, even if such a thin material is used, the exposed portion does not protrude outside the sealing portion of the exterior body, so that there is little possibility of breakage.

However, if the thickness is too small, wrinkles may occur when the paste containing the positive electrode mixture is applied, or the film may be broken by pulling in the preparation of the positive electrode. 10μ below
m or more is preferable.

In the lead portion on the positive electrode side, usually, an exposed portion of the current collector is left without forming a positive electrode mixture layer on a part of the aluminum current collector at the time of manufacturing the positive electrode, and the lead portion is used as the lead portion. Provided by However, the lead portion is not necessarily required to be integrated with the current collector from the beginning,
The current collector may be provided by connecting an aluminum foil or the like later.

In the present invention, a copper foil, a punched metal, a net, an expanded metal, or the like can be used as the current collector of the negative electrode, and usually, a copper foil is used. The current collector of the negative electrode has a thickness of 20 μm in order to reduce the thickness of the negative electrode.
The following are preferable. In the present invention, even if the thickness is so thin, the exposed portion does not protrude outside the sealing portion of the exterior body, so that there is little possibility of breakage.

However, if the thickness is too small, wrinkles may occur when the negative electrode mixture-containing paste is applied, or the film may be broken by pulling in the preparation of the negative electrode. 5 μm below
The above is preferred.

Also, the lead portion on the negative electrode side is usually used as a lead portion while leaving an exposed portion of the current collector without forming a negative electrode mixture layer on a part of the copper current collector at the time of producing the negative electrode. It is provided by. However, the lead portion on the negative electrode side is not necessarily required to be integrated with the current collector from the beginning, and may be provided by connecting a copper foil or the like to the current collector later.

As the metal plate for connecting the lead portion of the electrode and the external terminal, an aluminum plate is used for connecting the lead portion of the positive electrode and the positive terminal, and the metal plate for connecting the lead portion of the negative electrode and the negative terminal is used. Use copper ones.

The thickness of the connection metal plate is 10 to 30 regardless of whether it is made of aluminum or copper.
0 μm is preferred. That is, if the thickness is too thin, in connection with the lead portion of the electrode and the external terminal, not only not enough strength can be obtained, there is a risk of burning due to heat generated by current concentration during large current discharge,
On the other hand, if the thickness is too large, the adhesion between the adhesive layers of the outer package made of the laminate film is insufficient, and the sealing reliability may be lacking.
0 μm is suitable.

Nickel or nickel-plated metal foil or ribbon of iron, copper, stainless steel, etc. is used for the positive terminal and the negative terminal as external terminals because of the ease of connection with electronic equipment. Preferred, usually 40
Those having a thickness of about 100 μm are preferably used.

The connection between the lead portion of the electrode and the metal plate for connection and the connection between the metal plate for connection and the positive electrode terminal and the negative electrode terminal as external terminals may be performed by, for example, resistance welding, ultrasonic welding, laser welding, soldering, or the like. , Caulking, conductive adhesive, etc., but welding is particularly suitable.

As the outer package, for example, a three-layer laminated film composed of a polyester film-aluminum film-modified polyolefin film is used, and the modified polyolefin film has an adhesive action. The width of the sealing portion of the outer body is more advantageous from the viewpoint of strength as the width is wider, but if the width of the sealing portion of the outer body is increased, the outer body becomes larger, the volume and weight of the battery increase, and the size is reduced. If the width of the sealing portion is increased without changing the size of the exterior body, the electrodes must be reduced accordingly, which hinders the increase in capacity. It is preferable that the width of each of the joints is 1 mm or more and about 5 mm on both sides from the center of the connection part such as welding (that is, the width of the seal part is about 2 to 10 mm).

The positive electrode mixture and the negative electrode mixture are usually composed of an active material and, if necessary, an electron conduction aid and a binder. In the polymer electrolyte battery of the present invention, the positive electrode mixture and the negative electrode mixture are used. May also contain a gel-like polymer electrolyte. In such a case, a gel-like polymer electrolyte or the like is included in addition to a normal active material, an electron conduction aid, a binder, and the like. However, when preparing such a positive electrode mixture or a negative electrode mixture, the gel polymer electrolyte is in the state of an electrolytic solution containing a polymer or a monomer and a polymerization initiator, etc., which will constitute the gel polymer electrolyte by gelation. Prepared.

[0024]

Next, the present invention will be described more 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: 40 parts by weight of LiCoO ₂ powder, 8 parts by weight of flaky graphite powder and 5 parts by weight of polyvinylidene fluoride (hereinafter abbreviated as “PVdF”) powder were dry-mixed, and further mixed at 1.22 M (mol / mol). 1) Ethylene carbonate / propylene carbonate (hereinafter abbreviated as “EC / PC”) (50/50) solution 2 containing LiPF ₆
The paste containing the positive electrode mixture prepared by adding and mixing 5 parts by weight was applied to both sides of a 20 μm-thick aluminum foil serving as a current collector to a thickness of 75 μm, and then heated at 120 ° C. for 20 minutes. By forming a positive electrode mixture layer containing a gel polymer electrolyte on both sides of the aluminum foil (when the above-mentioned heating melts PVdF and the temperature decreases, the above-mentioned P
VdF gels, and at that time, PVdF
A non-fluidized positive electrode mixture is formed in the state of being taken in, and a sheet-shaped positive electrode is produced. This positive electrode is a so-called double-sided coated positive electrode. However, in manufacturing the positive electrode, the paste containing the positive electrode mixture was not applied to a portion to be a lead portion in the aluminum foil, and the aluminum foil was exposed. In addition, the EC / PC (50 /
50) indicates that the mixture of ethylene carbonate (EC) and propylene carbonate (PC) is a mixed solvent having a volume ratio of 50:50.

In Example 1, the positive electrode coated on both sides was
Each of the positive electrodes has a portion where the positive electrode mixture layer is formed is 76.5 mm × 92 mm on each surface.

Negative electrode: 40 parts by weight of spheroidal graphite powder, 4 parts by weight of flake graphite powder and 5 parts by weight of PVdF powder are dry-mixed, and then EC containing 1.22 M of LiPF ₆ is further added.
A negative electrode mixture-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 12%.
After applying a thickness of 75 μm on each side of the copper foil of μm, heating at 120 ° C. for 20 minutes to form a negative electrode mixture layer containing a gel polymer electrolyte on both sides of the copper foil,
A sheet-shaped so-called double-sided coated negative electrode was produced. In addition, as a negative electrode to be disposed on the outermost layer of the stacked electrode group, the negative electrode mixture-containing paste is applied to one surface of a copper foil, and heated in the same manner as above to form a negative electrode mixture layer on only one surface of the current collector. By forming, a sheet-like so-called single-sided coated negative electrode was produced. However, in any of the negative electrodes, the negative electrode mixture-containing paste was not applied to a portion to be a lead portion in the copper foil.

In Example 1, the double-sided coated negative electrode was
The negative electrode mixture layer was formed on both sides of the negative electrode mixture layer at 78.5 mm on both sides.
× 94 mm.

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.

The above-mentioned positive electrode uses four double-sided coated positive electrodes, the negative electrode uses three double-sided coated negative electrodes, two single-sided coated negative electrodes,
In addition, using eight polymer electrolyte layers, these positive electrodes,
A negative electrode, a polymer electrolyte, a negative electrode (this negative electrode is a single-sided coated negative electrode), a polymer electrolyte layer, a positive electrode,..., A negative electrode, a polymer electrolyte layer, a positive electrode, a polymer electrolyte layer, and a negative electrode (this negative electrode is also a single-sided coated negative electrode. , The middle three negative electrodes are both coated negative electrodes), and four positive electrodes and negative electrode 5
And eight polymer electrolyte layers to form a laminated electrode group.

An aluminum foil having a thickness of 100 μm, a width of 10 mm, and a length of 8 mm was prepared as a metal plate for connection with the lead portion of the positive electrode, and a metal plate having a thickness of 100 μm and a width of 10 mm was connected as a metal plate for connection with the negative electrode lead portion. A copper foil having a length of 10 mm and a length of 8 mm was prepared.

Then, the lead portions of the above-mentioned four positive electrodes and an aluminum foil as a connecting metal plate were welded with a 947M ultrasonic oscillator manufactured by Branson as a welding machine, for a welding time of 1 sec and a pressure of 3.2 kg / cm ^2. The ultrasonic welding was performed under the condition of an amplitude of 85%. The lead time of the five negative electrodes and the copper foil as the connection metal plate were welded for 1 hour.
sec, pressure 4kg / cm ² , amplitude 100
% Ultrasonic welding.

Two laminated films of a three-layer structure consisting of a polyester film, an aluminum film and a modified polyolefin film were prepared as an outer package for mounting the above-mentioned laminated electrode group, and a nickel ribbon having a thickness of 40 μm was used as a positive electrode terminal. Machine made by Branson, 94
A 7M ultrasonic oscillator is used to weld an aluminum foil as a connecting metal plate and a positive electrode terminal made of the above-mentioned nickel ribbon at a position to be a sealing portion of the above-mentioned outer package when the above-mentioned laminated electrode group is externally packaged. Time 75msec, pressure 2k
Ultrasonic welding was performed under the conditions of g / cm ² and 60% amplitude. Further, a nickel ribbon having a thickness of 40 μm was used as a negative electrode terminal, and a copper foil as a connecting metal plate and the nickel ribbon were used at a position to be a sealing portion of the external body when the laminated electrode group was externally mounted. The negative electrode terminal was subjected to ultrasonic welding under the conditions of a welding time of 120 msec, a pressure of 2 kg / cm ² and an amplitude of 60%, and thereafter, the laminated electrode group was packaged with a package. The outer packaging is performed by disposing the laminated electrode group between the two outer packagings, heating the overlapping portion of the peripheral portion, and melting and heat-sealing the innermost layer of the modified polyolefin film. Was. Therefore, the two exterior bodies were arranged so that the modified polyolefin films faced each other.

The welding width between the aluminum foil as the connecting metal plate and the positive electrode terminal was 2 mm, and the width of the sealing portion of the outer package was 4 mm. Further, the welding width between the copper foil as the connecting metal plate and the negative electrode terminal was 2 mm, and the width of the sealing portion of the exterior body was 4 mm as described above.

FIG. 1 is a cross-sectional view schematically showing the laminated polymer electrolyte battery of the first embodiment.
, A negative electrode 2 and five polymer electrolyte layers 3 to form a laminated electrode group, and the laminated electrode group is packaged with a package 4 composed of a three-layer laminated film of a polyester film-aluminum film-modified polyolefin film. Thus, a laminated polymer electrolyte battery is formed.

The laminated electrode group corresponds to a laminate in which four unit cells each including the positive electrode 1, the polymer electrolyte layer 3 and the negative electrode 2 and one negative electrode 2 are laminated.
In order to show the configuration of the anode and the negative electrode 2, one inner unit cell is taken out of the above-mentioned unit cells, and a 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 each of the positive electrode 1 and the negative electrode 2. As shown in FIG. Positive electrode mixture layers 1b on both sides of body 1a
The portion of the aluminum foil where the positive electrode mixture layer is not formed constitutes the lead portion 1c. The negative electrode 2 is a current collector 2a made of copper foil.
The negative electrode mixture layer 2b is formed on both surfaces of the copper foil, and the portion of the copper foil where the negative electrode mixture layer is not formed constitutes the lead portion 2c.

FIG. 3 shows a connection portion of the aluminum foil serving as the connection metal plate 7 on the positive electrode 1 side of the battery and the positive electrode terminal 5 by welding, and the vicinity thereof. This is done in part 4a. That is, the two exterior bodies 4 are used, and the sealing is performed by heat-sealing the modified polyolefin film of the laminate film used as the exterior body 4, but the sealing as the connection metal plate 7 on the positive electrode 1 side is performed. The connection between the aluminum foil and the positive electrode terminal 5 by welding is performed at the sealing portion 4a of the exterior body 4, and the connecting metal plate 7 and the positive electrode terminal 5 are connected.
Is located in the region of the sealing portion 4a of the exterior body 4. And the welding width is 2m as described above.
m, the width of the sealing portion 4a is 4 mm. Reference numeral 4b denotes a seal layer formed by melting the innermost modified polyolefin film of the outer package 4 by heating.
Corresponds to the sealing portion 4a of the outer package 4. The sealing layer 4b maintains the hermeticity of the inside of the battery, and the electrolytic solution to the connecting portion between the connecting metal plate 7 and the positive electrode terminal 5. Adhesion and air from the outside of the battery are prevented. Although not shown in FIG. 3, as schematically shown in FIG. 1, the connection by welding between the copper foil as the connection metal plate 7 on the negative electrode 2 side and the negative electrode terminal 6 is also performed on the positive electrode side. In the same manner, the welding is performed at the sealing portion 4a of the exterior body 4, the welding width is 2 mm, and the width of the sealing portion 4a is 4 mm.
It is.

FIGS. 1 to 3 are schematic diagrams, and the dimensional ratios of the components are not always accurate.

COMPARATIVE EXAMPLE 1 Four positive electrode leads were connected by welding at the sealing portion of the outer package in a state where four positive electrode leads were laminated without using the connecting metal plate as in Example 1, and A laminated polymer electrolyte battery was produced in the same manner as in Example 1, except that the five negative electrode leads were stacked and five negative electrodes were connected to the negative electrode terminal by welding at the sealing portion of the package.

After measuring the internal resistance of the batteries of Example 1 and Comparative Example 1, the batteries were stored in an atmosphere at 60 ° C. and a relative humidity of 90% for 20 days, and the internal resistance after storage was measured. Table 1 shows the results. The internal resistance was measured at a frequency of 1 kHz using a 4263B type LCR meter manufactured by Hewlett-Packard Company.

[0043]

[Table 1]

As shown in Table 1, the battery of Example 1 exhibited a smaller increase in internal resistance due to storage than the battery of Comparative Example 1, and had excellent storage characteristics. This is considered to be because the battery of Example 1 had a high sealing property, whereas the battery of Comparative Example 1 had a low sealing property because the lead portion in the sealing portion of the outer package was thick.

[0045]

As described above, according to the present invention, it is possible to provide a laminated polymer electrolyte battery having high sealing performance at the sealing portion of the outer package, excellent storage characteristics, and high reliability of battery performance. .

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically illustrating an example of a laminated polymer electrolyte battery according to Example 1 of the present invention.

FIG. 2 is a cross-sectional view schematically illustrating a main part of one unit cell of a stacked electrode group used in the stacked polymer electrolyte battery according to the first embodiment of the present invention.

FIG. 3 is a cross-sectional view schematically showing a connecting portion of a positive electrode-side connecting metal plate and a positive electrode terminal as an external terminal and the vicinity thereof in the laminated polymer electrolyte battery of Example 1 of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Aluminum current collector 1b Positive electrode mixture layer 1c Lead part 2 Negative electrode 2a Copper current collector 2b Negative electrode mixture layer 2c Lead part 3 Polymer electrolyte layer 4 Outer body 4a Seal part 5 Positive terminal 6 Negative terminal 7 Connection metal plate 8 Connection part between connection metal plate and positive electrode terminal

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H022 AA09 BB11 CC02 CC08 CC12 CC16 EE01 KK08 5H029 AJ06 AJ15 AK03 AL07 AM16 BJ04 BJ12 DJ05 DJ07 EJ01

Claims (1)

[Claims] 1. A plurality of positive electrodes each having a positive electrode mixture layer formed on at least one surface of an aluminum current collector and a negative electrode mixture layer formed on at least one surface of a copper current collector. A plurality of negative electrodes, a laminated polymer electrolyte battery in which a laminated electrode group in which a polymer electrolyte layer is interposed between each of the positive electrode and the negative electrode is packaged with a package; A current collector of at least one electrode and a lead portion of the same material are connected to a connection metal plate of the same material as the lead portion, and an external terminal of a different material from the connection metal plate and the lead portion of the electrode. Are connected by a sealing portion of an exterior body.