JP2000215879A - Polymer electrolyte battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent corrosion of a part of a current collector of an electrode or a lead body connected to the current collector, which is drawn out from an exterior body, and to prevent deterioration of storage characteristics and the like. I will provide a. SOLUTION: A sheet-like positive electrode 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 current collector for the positive electrode or an aluminum lead connected to the current collector and a current collector for the negative electrode in a polymer electrolyte layer having a sheet-shaped negative electrode and a polymer electrolyte, which are packaged with a package. The free end side of the body or the copper lead body connected to the current collector is pulled out from the sealing portion of the exterior body, and the portion outside the sealing portion of the exterior body is nickel or nickel-plated copper, iron or Coated with a metallic coating such as stainless steel to prevent them from contacting the outside air.

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 polymer electrolyte battery particularly 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. In particular, batteries using polymer electrolytes have excellent safety and storage properties including leak resistance,
In addition, because it is thin and flexible, it 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 package with the above package, a thin battery is completed.

[0004]

In this polymer electrolyte battery, in order to make the electrode thin, a metal foil is usually used as a current collector, an aluminum foil is used as a positive electrode current collector, and a negative electrode is used as a current collector. Copper foil is used for the current collector. And, as the external terminal of the battery, that is, the positive electrode terminal and the negative electrode terminal used for connection with the battery using device, a nickel foil or ribbon is usually used because of easy connection with the battery using device. .

The electrical connection between these electrodes and external terminals is
Normally, the positive electrode mixture layer is not formed on a part of the aluminum foil at the time of manufacturing the positive electrode, and the exposed portion of the aluminum foil is left, and this is used as a connection portion with the positive electrode terminal as an external terminal, or The aluminum lead body is connected to the part by ultrasonic welding, etc., and the free end side of the aluminum lead body is used as the connection part with the positive terminal as an external terminal. Leave the exposed portion of the copper foil without forming the negative electrode mixture layer on it and use it as a connection part with the negative electrode terminal as an external terminal, or free of the copper lead body connected to the exposed portion of the copper foil The end side is a connection portion with a negative electrode terminal as an external terminal.

[0006] However, welding of aluminum and nickel on the positive electrode side is very difficult. Usually, welding is performed by resistance welding, ultrasonic welding, or the like. There has been a problem that the presence of the electrolytic solution causes corrosion of aluminum. In order to prevent the connection part by the above welding from coming into contact with the electrolytic solution, there is a method of welding an aluminum foil or an aluminum lead body to a nickel external terminal at a seal part, but it is necessary to weld at a narrow part. And there was a problem that it was technically difficult.

Therefore, it is conceivable to directly pull out an aluminum foil or an aluminum lead body or a copper foil or a copper lead body outside the sealing portion of the exterior material (aluminum laminated film), but the operation itself is easy. However, these metals have low strength and are susceptible to corrosion. Moreover, if they are directly connected to equipment using batteries, there is a problem that sufficient welding strength cannot be obtained. Required some external terminals.

Accordingly, the present invention solves the above-mentioned problems of the prior art, in which an aluminum foil or a copper foil used as a current collector of an electrode is drawn out from a sealing portion of an exterior body. Another object of the present invention is to provide a highly reliable polymer electrolyte battery by preventing such corrosion and suppressing deterioration of battery characteristics such as deterioration of storage characteristics due to corrosion.

[0009]

SUMMARY OF THE INVENTION The present invention provides a sheet-like positive electrode comprising a positive electrode mixture layer formed on at least one surface of an aluminum current collector, and a copper current collector on at least one surface of a copper current collector. In a polymer electrolyte layer having a sheet-shaped negative electrode and a polymer electrolyte formed by forming a negative electrode mixture layer, and covering them with a package, the aluminum current collector or the aluminum current collector of the positive electrode The free end side of the connected aluminum lead body and the copper current collector of the negative electrode or the copper lead body connected to the copper current collector is pulled out from the sealing portion of the exterior body, and the The outer part of the seal is covered with a metallic coating such as nickel or nickel-plated copper, iron or stainless steel, so that they do not come into contact with the outside air. It is obtained by solving the above problems.

That is, by adopting the above configuration,
Corrosion of the aluminum current collector or the aluminum lead connected to the aluminum current collector or the copper current collector or the copper lead connected to the copper current collector is prevented, and the corrosion is prevented. A reduction in battery performance based on, for example, a reduction in storage characteristics is prevented. In addition, the above-mentioned coating material is used for the positive electrode aluminum current collector or the aluminum lead body connected to the aluminum current collector or the negative electrode copper current collector or the copper current collector connected to the copper current collector. Since the portion of the lead body outside the sealing portion of the exterior body is protected, cutting, breakage, and the like due to insufficient strength thereof are prevented. Further, by extending the free end side of the covering material, it can be used as an external terminal, and by connecting the external terminal to the covering material, connection with a battery-using device becomes easy.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, as a current collector of a positive electrode, aluminum foil, punched metal, mesh, expanded metal, etc. can be used, and aluminum foil is particularly suitable. The current collector of the positive electrode preferably has a thickness of 20 μm or less in order to reduce the thickness of the positive electrode. However, if it is too thin, in making the positive electrode,
Wrinkles occur when applying the positive electrode mixture-containing paste,
Since the film may be broken by pulling, the thickness is preferably 20 μm or less and 10 μm or more as described above.

When an aluminum lead body is used, the thickness of the aluminum lead body is 40 mm.
１００100 μm is preferred. Such a lead body is preferably used particularly when the current collector of the positive electrode is thin and it is not preferable to draw it out of the exterior body in terms of strength.

Further, as a current collector of the negative electrode, copper foil,
Punched metal, mesh, expanded metal, etc. may be used, but copper foil is particularly suitable. The thickness of the current collector of the negative electrode is 5 to 20 μm in view of reducing the thickness of the negative electrode.
Is suitable. That is, if the current collector is too thin, in the production of the negative electrode, when the paste containing the negative electrode mixture is applied, there is a possibility that wrinkles may occur or tears may occur due to tension, and if the current collector is too thick, the negative electrode Therefore, the thickness of the current collector of the negative electrode is preferably 5 to 20 μm as described above.

When a copper lead is used, the thickness of the copper lead is preferably 40 to 100 μm.

The coating material is made of nickel or a metal such as nickel-plated iron, copper, stainless steel or the like, and is preferably in the form of a foil or a ribbon, and the thickness is preferably 30 to 100 μm. The use of such metals as the coating material is because they are easy to connect to battery-powered equipment when they are used as such as external terminals such as a positive electrode terminal and a negative electrode terminal, or they are nickel or nickel plated. This is because it is easy to weld when external terminals made of metal such as iron, copper, and stainless steel are welded, and the thickness of the coating material is preferably 30 to 100 μm. By setting the thickness of the coating material to 30 μm or more, it is possible to prevent cutting during welding with a current collector or a lead body, prevent tearing due to pulling or bending, and reduce the thickness to 1 μm.
By setting the thickness to 00 μm or less, an increase in weight and a decrease in energy density can be prevented.

The method of covering the outer portion of the current collector or the outer body of the lead body from the sealing portion with the covering material is not particularly limited, and various methods can be adopted. To cover a portion (exposed portion) outside the seal portion of the current collector or the exterior body of the lead body, or sandwich the exposed portion from above and below with a covering material in a sheet shape (sandwich in a U-shape state). In order to prevent the above-mentioned exposed portion from coming into contact with the outside air, the open peripheral portion and the like may be sealed by welding or bonding.
However, the coating method is not limited to the method described above.

The coating material is combined with an aluminum current collector for the positive electrode, an aluminum lead connected to the current collector, a copper current collector for the negative electrode, or a copper lead connected to the current collector. As a connection method, for example, various methods such as resistance welding, ultrasonic welding, laser welding, soldering, caulking, and a method using a conductive adhesive can be adopted, and welding is particularly suitable.

As the outer package, for example, a laminate film having a three-layer structure composed of a polyester film or a nylon-aluminum film-modified polyolefin film is used, and the modified polyolefin film serves as an adhesive layer. The wider the sealing portion of the outer package is, the more advantageous from the viewpoint of strength. However, if the width of the sealing portion of the outer package is increased, the outer package becomes larger, the volume and weight of the battery increase, and the size is reduced. If you increase the width of the seal part without changing the size of the exterior body,
The width of the sealing portion is 2 to 10 mm because the electrodes must be reduced accordingly, which hinders an increase in capacity.
The degree is preferred.

[0019]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples. In addition, the manufacturing method of the positive electrode, the negative electrode, and the polymer electrolyte layer, which are common parts in the following examples and the like, will be described prior to the description of the examples and the like.

Preparation of positive electrode: LiCoO as positive electrode active material
₂ 50 parts by weight, acetylene black 10 is a conductive aid
Parts by weight and 10 parts by weight of polyvinylidene fluoride as a binder were uniformly mixed, and 40 parts by weight of an electrolytic solution were further added and mixed to prepare a positive electrode mixture-containing paste.
The electrolyte solution was prepared by mixing LiPF _{6 in} a mixed solvent of propylene carbonate and ethylene carbonate at a volume ratio of 1: 1.
22 mol / liter dissolved. Then, the positive electrode mixture-containing paste prepared as described above is applied to one surface of a 20 μm-thick aluminum foil serving as a current collector,
By heating and gelling, a gel-like positive electrode mixture layer was formed on the aluminum foil to produce a sheet-like positive electrode. However, in producing the above positive electrode, the exposed portion of the aluminum foil is left without applying the positive electrode mixture-containing paste to part of the aluminum foil, and the free end side of the exposed portion is pulled out from the sealing portion of the exterior body. Part.

Preparation of Negative Electrode : A negative electrode mixture-containing paste was prepared by mixing 40 parts by weight of graphite as the negative electrode active material, 5 parts by weight of polyvinylidene fluoride, and 55 parts by weight of the same electrolytic solution as used for the above positive electrode. Then, the negative electrode mixture-containing paste is applied to one surface of a copper foil having a thickness of 20 μm serving as a current collector, and heated to gel to form a gel-like negative electrode mixture layer on the copper foil. Thus, a sheet-shaped negative electrode was produced. However,
In preparing the above negative electrode, a part where the exposed part of the copper foil is left without applying the negative electrode mixture-containing paste to a part of the copper foil, and the free end side of the exposed part is drawn out from the sealing part of the exterior body. And

Preparation of polymer electrolyte layer: A polyolefin non-woven fabric having a thickness of 70 μm was used as a support, and this non-woven fabric was mixed with 15 parts by weight of a mixture of three acrylic monomers and 0.75 parts by weight of benzoyl peroxide as a polymerization initiator. Impregnated with a mixed solution of the same electrolyte solution 85 parts by weight, heated to polymerize the monomer and gelled the whole,
A sheet-like gel polymer electrolyte layer was prepared. The acrylic monomer mixture is a mixture of 2-ethoxyethyl acrylate, triethylene glycol dimethacrylate, and ethylene glycol ethyl carbonate methacrylate at a weight ratio of 50:13:33.

This polymer electrolyte layer is disposed between the above-mentioned positive electrode and negative electrode, and pressed to form a unit cell. A laminated film having a structure was prepared.

Example 1 An aluminum foil serving as a current collector for a positive electrode and a copper foil serving as a current collector for a negative electrode were each connected to a copper foil having a thickness of 40 μm.
Prepare a nickel ribbon, and when the unit cell is packaged with the package, cover the portion drawn out from the sealing portion of the package of the aluminum foil of the positive electrode with the coating material made of the nickel ribbon, using an ultrasonic welding machine. 75m welding time
A coating material comprising the above-mentioned nickel ribbon, a portion of which is subjected to ultrasonic welding under the conditions of a pressure of 2 kg / cm, an amplitude of 60%, and a portion drawn out of a sealing portion of a copper foil outer casing as a negative electrode current collector. And ultrasonically welded by an ultrasonic welding machine under the conditions of a welding time of 120 msec, a pressure of 2 kg / cm, and an amplitude of 60%. Welding was performed on both the positive electrode side and the negative electrode side by welding the entire outer portion of the aluminum foil or copper foil outside the sealing portion of the sheath and the overlapped portion with the covering material. The width of the sealing portion of the exterior body was 4 mm.

The schematic structure of the above battery will be described with reference to FIG. 1 and FIG. 2. A sheet-like polymer electrolyte layer 3 is disposed between a sheet-like positive electrode 1 and a sheet-like negative electrode 2 to form a unit cell. The unit cell is constructed and packaged with a package 4 made of a laminate film. And
The free end side of the aluminum foil used as the current collector 1a of the positive electrode 1 is drawn out from the sealing portion of the exterior body 4, and the current collector 1a made of the aluminum foil is covered with the coating material 5. The coating material 5 is also used as a positive electrode terminal, and the free end of the coating material 5 can be used for connection to equipment to be used. Further, the free end side of the copper foil used as the current collector 2a of the negative electrode 2 is drawn out from the sealing portion of the exterior body, and the current collector 2a made of the copper foil is covered with the coating material 6, The coating material 6 also serves as a negative electrode terminal, and its free end is used for connection to equipment to be used.

FIG. 2 shows a portion of the current collector 1a of the positive electrode 1 of the battery drawn out from the sealing portion of the outer package 4 and the vicinity thereof. As shown in FIG. Are used, and the sealing is performed by heat-sealing the modified polyolefin sheet of the laminate film used as the outer package 4, and the current collector 1 of the positive electrode 1 is sealed.
a is made of an aluminum foil as described above, and the positive electrode 1 is produced by forming a gel-like positive electrode mixture layer 1b on one surface of a current collector 1a made of the aluminum foil. The current collector 2a of the negative electrode 2 is made of copper foil as described above, and the negative electrode 2 is formed by forming a gel-like negative electrode mixture layer 2b on one surface of the current collector 2a made of this copper foil. Have been.

The covering material 5 covers a portion of the current collector 1a made of aluminum foil of the positive electrode 1 which is drawn out from the sealing portion 4a of the exterior body 4 of the current collector 1a. Although not shown in FIG. 2, a portion of the current collector 2 a made of copper foil of the negative electrode 2, which is drawn out from the sealing portion 4 a of the exterior body 4, is covered with a coating material 6. 1 and 2
Is a schematic illustration, and the dimensional ratio of each component is not always accurate.

COMPARATIVE EXAMPLE 1 A portion of the aluminum foil used as a current collector for the positive electrode, which was drawn out of the sealing portion of the outer package, was not covered with a coating material, and was used as a current collector for the negative electrode. A polymer electrolyte battery was produced in the same manner as in Example 1, except that the portion of the copper foil that had been drawn out from the sealing portion of the outer package was not covered with the coating material.

Next, the internal resistance and load characteristics of the batteries of Example 1 and Comparative Example 1 were measured. Table 1 shows the results. The above internal resistance is 20% in a so-called initial (immediately after production) battery at 60 ° C. and 90% RH
The battery after storage for a day was measured, and the measurement was performed by a 1 kHz alternating current method using an LCR meter. The load characteristics of the first battery were 4.2
V, charged at a constant current and a constant voltage of 0.2 C for 8 hours, discharged at a current density of 1 C and a discharge current of 0.2 C to 2.75 V, respectively, and measured the discharge capacity. The ratio (percentage) divided by the discharge capacity when discharging at a density of 0.2 C [(discharge capacity at 1 C / discharge capacity at 0.2 C) × 100] was evaluated. However, in Table 1, this is simplified and shown by the item “load characteristics (1C / 0.2C)”.

[0030]

[Table 1]

As shown in Table 1, the battery of Example 1 has a smaller increase in internal resistance due to storage and has better storage characteristics than the battery of Comparative Example 1.

On the other hand, the battery of Comparative Example 1 has a large increase in internal resistance due to storage, which causes a decrease in various battery performances including load characteristics. Thus, Comparative Example 1
The increase in the internal resistance due to the storage of the battery is considered to be due to the large corrosion of the aluminum foil and copper foil used as the current collector of the electrode, particularly the aluminum foil.

In the above embodiment, a case was shown in which one unit cell was packaged to finish the battery, but instead, a unit cell laminate in which a plurality of unit cells were laminated was packaged to form the battery. May be finished.

When the polymer electrolyte is gelled, in addition to those shown in the above Examples, for example, a radical polymerizable unsaturated polyester or a radical polymerizable acrylic epoxy acrylate, urethane acrylate, polyester acrylate, alkyd A photocurable resin such as acrylate or silicon acrylate may be gelled using ultraviolet light or an electron beam. In addition, the preparation of the polymer electrolyte layer is also performed by preparing electrodes such as a positive electrode and a negative electrode in a normal state that is not gelled, surrounding the periphery with a support such as a nonwoven fabric, and impregnating the electrolyte containing a gelling component. A gel polymer electrolyte may be formed by gelation.

[0035]

As described above, according to the present invention, it is possible to provide a polymer electrolyte battery having excellent storage characteristics such as a small increase in internal resistance due to storage and having high reliability in battery performance.

[Brief description of the drawings]

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

FIG. 2 is an enlarged view of a main part of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 1a Current collector 1b Positive electrode mixture layer 2 Negative electrode 2a Current collector 2b Negative electrode mixture layer 3 Polymer electrolyte layer 4 Outer body 4a Seal part 5 Coating material 6 Coating material

Claims (1)

[Claims] 1. A sheet-like positive electrode 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. In a polymer electrolyte battery having a sheet-shaped negative electrode and a polymer electrolyte,
The aluminum current collector of the positive electrode or the aluminum lead body connected to the aluminum current collector and the copper current collector of the negative electrode or the exterior body of the copper lead body connected to the copper current collector The outer portion of the sealing portion is covered with a metal coating material such as nickel or nickel-plated copper, iron or stainless steel, and is connected to the aluminum current collector or the aluminum current collector. A polymer electrolyte battery, wherein a portion outside a sealing portion of a lead body made of copper and a current collector made of copper or a sheath of a copper lead body connected to the current collector made of copper is prevented from contacting with outside air. .