JPH0475254A - Secondary battery - Google Patents

Abstract

PURPOSE:To provide a terminal which is electrically and mechanically excellent and enhance reliability of a secondary battery by sandwiching an aluminium electrode current collector of predetermined thickness between metals having predetermined hardness each, and electrically connecting each metal to aluminium. CONSTITUTION:The thickness of an aluminium current collector is less than 200mum. Two metals having Vickers hardness more than 40mum each and used for sandwiching aluminium between them are of the same kind. Ultrasonic welding is preferable as connecting method from the point of view of reproducibility, electrical properties and mechanical properties. The time required for ultrasonic welding is 0.1 to 10min, pressurizing forces are 0.5 to 7kg/cm<2>, output frequency is 20 to 40kHz.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a secondary battery.

[Prior Art] In recent years, as devices have become smaller, lighter, and more portable, there has been a demand for smaller, lighter, thinner, and longer-life batteries for the batteries that serve as their power sources.

Aluminum is lightweight and has excellent workability, so when used as a current collector for electrodes, it is possible to form lightweight batteries with high energy density. Proposals have been made for use in current collectors. In addition, aluminum forms an alloy with lithium and can be used as an active material that is stable against repeated charging and discharging, and an electrode in which L1-A1 alloy is supported on a current collector is highly recommended as a negative electrode for secondary batteries. Energy density and high cycle life.

However, electrodes using aluminum as a current collector have many problems in terms of terminal extraction. For example, metals or alloys such as aluminum, Ni, and stainless steel cannot be joined by arc welding, etc., and soldering requires forming a terminal cell at the terminal, and bonding with a conductive adhesive requires bonding with an electrolyte. There were problems in terms of reduced strength and conductivity. In the field of capacitors, aluminum electrodes are ultrasonically welded to aluminum lead plates to form terminals, but problems remain in connection between the aluminum lead plate and external circuits, and this aluminum electrode is used as an electrode current collector used in the battery field. It is thicker than the original, and the aluminum lead plate is also thicker. The thickness of the aluminum used for the current collector of secondary batteries is too soft, so the welded part stretches, becomes thinner, and eventually breaks, resulting in an electrical
Mechanical connections are likely to be defective. Furthermore, since the terminal portion is quite thick, it becomes an obstacle when mounting the sheet-like electrode on various types of batteries.

[Problems to be Solved by the Invention] In view of these actual circumstances, an object of the present invention is to provide a secondary battery that eliminates the above-described drawbacks in the terminal portion.

[Means for Solving the Problems] As a result of intensive studies on the above problems, the inventors have found that:
An electrode terminal can be made by sandwiching aluminum between metals or alloys with a Vickers hardness of 50 or more and electrically connecting them by welding. Even if 200μI
We have found that the following also have excellent mechanical and electrical properties, leading to the present invention.

That is, the present invention provides a secondary battery using a sheet-like electrode having a thickness of 200 μm or less aluminum as an electrode current collector, in which a part of the current collector is sandwiched between metals or alloys having a Vickers hardness of 40 or more, and the metal Alternatively, it is a secondary battery characterized in that the alloy is electrically connected with aluminum to form a terminal portion.

The thickness of the aluminum current collector in the present invention is 20
It is 0 μm or less, preferably 5 μIl to 150 μm.

If it exceeds 200 μl, the weight of the aluminum current collector becomes large, and the merit of lightness decreases.

As the metal or alloy having a Vickers hardness of 40 or more, metals with high electrical conductivity such as copper, nickel, and stainless steel are used. It is preferable that the two metals or alloys having a Vickers hardness of 40 μM or more sandwiching the aluminum are of the same type, but may be different.

The thickness of the metal or alloy having a Vickers hardness of 40 or more is 5 to 100 .mu.m, preferably 10 to 70 .mu.m. If it is less than 5μI, it is disadvantageous in terms of strength, and if it is less than 100μ-
If it exceeds this, the terminal will become thick and heavy.

Connection methods include ultrasonic welding and spot welding.

Examples include laser welding and plasma welding, but ultrasonic welding is preferred in terms of reproducibility, electrical properties, and mechanical properties.

Ultrasonic welding time is 0.1~10 seconds, pressure is 0.5~7)cg/cgf, output frequency is 2
0-40KHz is used.

The electrode terminal portion of the present invention can further be provided with lead wires and lead plates for connection to an external circuit by pressure welding, conductive adhesive, soldering, welding, or the like. Furthermore, the electrode terminal portions of the secondary battery of the present invention may be attached before the active material is supported, or may be attached after the active material is supported or even during battery mounting.

The electrode of the present invention can be applied to devices such as secondary batteries, capacitors, electrochromic devices, transistors, solar cells, etc., but is most effective when used as an electrode for secondary batteries.

Next, a secondary battery using the electrode of the present invention will be explained.

The battery of the present invention basically consists of a positive electrode, a negative electrode, and an electrolyte.

As active materials for the positive electrode, metal chalcogen compounds such as M o S T i S2'2 VO, MnO, and CaO2, polypyrrole, polyacetylene, poly3-methylthiophene, polyaniline, polyparaphenylene, polydiphenylbenzidine, polyazulene, polycarbazole, etc. Among these conductive polymer materials, conductive polymer materials are most preferable in terms of lightness and flexibility.

The negative electrode active materials include Li, All, Pb, and St.

Alloys such as Ga, In, and Mg, and conductive polymers such as polyacetylene, polythiophene, and polypyridine.

Although a carbon body can be used as an example, L L-Al1 alloy is most preferable in terms of cycle life.

The solvent constituting the electrolyte solution is not particularly limited, but a relatively highly polar solvent is preferably used.

Specifically, propylene carbonate, ethylene carbonate, and benzonitrile.

Acetonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butyl lactone, dioxolane,
Triethyl phosphate, triethyl phosphite, dimethylformamide, dimethylacetamide, dimethyl sulfoxide.

Dioxane, dimethoxyethane, polyethylene glycol, sulforane, dichloroethane, chlorobenzene,
One or a mixture of two or more organic solvents such as nitrobenzene can be mentioned.

As electrolytic salts, LiPF, LiSbF6゜Li
AsF , LiCgO, NaCl0. .

K I , K P F , K S b F , K
A s F e .

K C10, [(n B u ) N 3 , A
s F e [(n-Bu) Nl ” ・CD O
,-[(n-Bu)Nl''・BF4- L I A II CI , L i B F ,
Examples include L i CF a S O3.

As the separator, one is used that has low resistance to ion movement of the electrolyte solution and has excellent solution retention. For example, a glass fiber filter; a polymer bore filter such as polyester, Teflon 1 Polyflon, or polypropylene; a nonwoven fabric; or a nonwoven fabric made of glass fiber and these polymers can be used.

Moreover, a solid electrolyte can also be used as a component in place of these electrolytes and separators. For example, in inorganic systems, AgCJ, AgBr, Ag I.

Metal halides such as Li1, RbAg415°Rb
Examples include Ag414CN. In addition, in organic systems, polyethylene oxide, polypropylene oxide, polyvinylidene fluoride, polyacrylamide, etc. are used as a polymer matrix, and the above-mentioned electrolyte salt is dissolved in the polymer matrix to form a composite, or a crosslinked product of these, and low molecular weight polyethylene oxide. , a polymer electrolyte in which an ionic dissociative group such as a crown ether is grafted onto a polymer main chain, or a gel electrolyte in which an electrolyte is supported on a high molecular weight polymer.

Although the form of the battery is not particularly limited, it can be mounted in various types of batteries such as coin type, sheet type, cylindrical type, and gum type.

[Example] The present invention will be explained in more detail with reference to Examples below.

Example 1 Aluminum foil with a purity of 99.99% (thickness 50 x 90
X O, Hm) was roughened by applying a 50 V DC voltage in an electrolytic solution containing hydrochloric acid (surface area: 30 times that of a flat foil)
.

As shown in Figures 1 and 2, 5 x 30 x O, H dragon and 5 x 5 x O, 0: (U) Ni foil was sandwiched with aluminum foil and 3 kg was ultrasonically welded for 0.1 seconds. Terminal section The connection had sufficient strength.

Next, using this alkonium foil as an anode, an anodic oxide film (approximately 30 ml thick) was formed by applying 2 volts of 20 g/II aqueous solution of ammonium adipate as an electrolyte. Next, the aluminum foil on which the anodized film was formed (hereinafter simply referred to as aluminum foil) was immersed in a 20 tr/1 aqueous solution of ammonium persulfate for 5 minutes, and then immersed in a 10 tr/fl ethanol solution of virol monomer to coat the surface of the aluminum foil. A chemically oxidized polymerized virol film was formed.

The treated aluminum foil was immersed in an electrolytic solution containing 0.2 mol/N of paratoluenesulfonic acid and 0.3 mol/1 of virol, and a constant current of 0.5 mA/c was applied using this as an anode and a stainless steel plate as a cathode. Electrolytic polymerization was performed to produce a polypyrrole/l electrode.

Comparative Example 1 Ultrasonic welding was attempted on a 5 x 30 x O, 03111I Ni foil alone. It was impossible to install the terminal due to the breakage of the aluminum.

Comparative Example 2 Using aluminum solder, 5 x 30 x O,0
The terminal portion was installed in the same manner as in Example 1 except that the connection was made using only the B+n Ni foil. Although the connection was good, the connection was not flat as shown in FIG.

Example 2 Etched foil for capacitor (50X 90Xo, 07m
m) 45 μl of Li was vacuum deposited on top. This at 120℃
A Li-Al1 alloy electrode was obtained by heating to . This is 5 X 30 X O, 05 and 5 X 5 X
As shown in Figure 1, cut the Ni foil in the order of O, 05 with scissors 3.5
kg, and terminals were formed by ultrasonic welding for 0.08 seconds.

Comparative Example 3 An electrode was obtained in the same manner as in Example 2 except that a Ni foil of 5 x 30 x 0.05 mm was used alone. The welds were not completely connected, only partially connected.

Battery test example 1. The electrode manufactured in Comparative Example 2 was used as the positive electrode, the electrode manufactured in Example 2 was used as the negative electrode, and the separator was a polypropylene microporous membrane impregnated with 3M LBF4/propylene carbonate + dimethoxyethane (7:3). A battery as shown in FIG. 4 was manufactured using a heat-sealable film having a three-layer structure of polyester/Aft/polyethylene as the agent.

A battery was manufactured in the same manner as above using the electrode of Comparative Example 3 as a negative electrode and the electrode of Example 1 as a positive electrode.

Table 1 shows the battery performance.

Table 1 [Effects of the Invention] As explained above, the secondary battery of the present invention has terminal parts that are electrically and mechanically excellent, and has high performance and reliability.

[Brief explanation of drawings]

1 and 2 are diagrams illustrating an example of the structure of the terminal section in the secondary battery of the present invention, in which FIG. 1 is a plan view, FIG. 2 is a side view, and FIG. 3 is a diagram of the terminal section in Comparative Example 3. FIG. 4 is a diagram illustrating the connection state, and FIG. 4 is a diagram schematically illustrating the configuration of the secondary battery of the present invention that was subjected to a battery test. Figure 1 Figure 4 Positive electrode active material Figure 2

Claims (2)

[Claims] (1) In a secondary battery using a sheet-like electrode in which aluminum with a thickness of 200 μm or less is used as an electrode current collector, a part of the current collector is sandwiched between metals or alloys with a Vickers hardness of 40 or more, and the metals or alloys are replaced with aluminum. A secondary battery characterized by using an electrode which is electrically connected to the electrode and serves as a terminal part. (2) The secondary battery according to claim (1), wherein the electrical connection is made by ultrasonic welding.