JPS62108473A - Cell - Google Patents

Abstract

PURPOSE:To improve the charge/discharge characteristic and to reduce the size and the thickness by integrating a negative electrode employing a lithium alloy as a negative electrode active material and an outer can, thereby preventing increase of the inner resistance caused by insufficient electrical contact. CONSTITUTION:An aluminum base disc is spot welded to the inside of a stainless steel outer can. While employing the aluminum section of the integrated aluminum base/outer can as a functioning electrode, lithium metal as a pair electrode and propylene carbonate solution of LiClO4 as electrolyte, an integrated unit of negative electrode and outer can is formed through such method as the aluminum base body is lithium alloyed to produce a lithium-aluminum alloy. Then it is combined with a positive electrode employing polyaniline as an active material to form a coin type cell. Consequently, the electrical contact performance is improved and the inner resistance is reduced, while the size and thickness can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Upgrade The present invention relates to a battery that uses a lithium alloy as a negative electrode active material, which has low internal resistance and excellent manufacturability.

What is the conventional technology and how to solve the problem of lithium alloy as a negative electrode? The battery used as 5fR has a higher energy density than conventional batteries, and also has tJ & ff when using the battery.
Lithium alloying can prevent the formation of dendrites caused by metal lithium, and is attracting attention as a long-life, high-energy density battery, especially as a secondary battery with excellent charge-discharge characteristics. .

However, batteries using these lithium alloys as negative electrode active materials, like other general batteries, usually have a negative electrode and an outer case prepared separately, and when assembling the battery, the negative electrode and the outer case are brought into sufficient electrical contact. It is necessary to assemble the
There is a problem in that it is difficult to obtain sufficient electrical contact between the negative electrode and the outer can simply by directly contacting the negative electrode and the outer can.

Conventionally, methods such as forming a current collector such as a mesh between the electrode and the outer can or installing a spring-like structural member have been adopted in order to make sufficient electrical contact between the electrode and the outer can. However, when a lithium alloy is used as a negative electrode active material, the brittleness of the lithium alloy may cause the negative electrode to chip during battery manufacture, or the negative electrode and outer case may change due to changes in volume during battery use. If the electrical contact with the battery becomes poor, the internal resistance of the battery will increase. Especially in the case of secondary batteries, as the battery is repeatedly charged and discharged, the internal resistance of the battery will increase and the charging/discharging characteristics will deteriorate. There is a problem that charging Mffi becomes impossible, and the process of assembling the battery becomes complicated due to the formation of the current collector and the installation of spring-like structural members. is the miniaturization of batteries,
There was also the problem that it became an impediment to thinning.

The present invention has been made in view of the above circumstances, and it solves the problem of poor electrical contact and maintains internal resistance at a low level. A lithium alloy that does not increase internal resistance due to poor electrical contact, allows its charging and discharging characteristics to be fully demonstrated over a long period of time, simplifies the battery manufacturing process, and can be easily made smaller and thinner. The purpose of the present invention is to provide a battery using the material as a negative electrode active material.

In order to achieve the above object, the inventors of the present invention have conducted intensive studies and found that the above object can be achieved by integrating a negative electrode containing a lithium alloy as a negative electrode active material and an outer can. This knowledge led to the completion of the present invention.

Therefore, in the present invention, the negative electrode and the outer can are integrally formed,
The present invention also provides a battery using a lithium alloy as a negative electrode active material.

The present invention will be explained in more detail below.

The battery of the present invention uses a lithium alloy as the negative electrode active material, but the lithium alloy used as the negative electrode active material of the battery of the present invention may be any alloy of lithium and a metal that can be alloyed with lithium. There are no particular limitations, and examples include alloys of lithium and eleven or more of aluminum, magnesium, indium, mercury, zinc, cadmium, and the like. Among these lithium alloys, alloys of aluminum, indium, or zinc with lithium are the most preferred because they have excellent formability and can be manufactured directly into negative electrode substrates without using current collectors such as mesh. It is suitable as a negative electrode active material for the battery of the invention.

Next, in the battery of the present invention, the negative electrode containing this lithium alloy as the negative electrode active material is integrated with the outer can, but in this case, if the negative electrode and the outer can are integrated, the integration is particularly difficult. There are no particular restrictions on the method.

Various methods can be used to obtain the composite body of the present invention in which the negative electrode and the outer can are integrated, depending on the type of material of the negative electrode substrate and the outer can. For example, a lithium alloy is formed in advance, Methods include joining or integrating with the outer can, but since the lithium alloy used as the negative electrode active material of the present invention is brittle, joining the negative electrode made of a lithium alloy with the outer can may cause chipping or other problems during bonding. Therefore, it is necessary to use a metal that can be alloyed with lithium with excellent formability such as aluminum, indium, or zinc for the negative electrode base, and to bond this negative electrode base to the outer can in advance before alloying the negative electrode base with lithium. In particular, it is preferable to use a lithium alloy partner metal for the outer can, and directly alloy a portion of the outer can with lithium, since it is possible to simplify the bonding process and to construct a thin battery. preferable. Note that as a method for joining the negative electrode or negative electrode substrate and the outer can, adhesion, welding, ha/v, etc. can be used as appropriate depending on the material, shape, size, etc. Various methods can also be used to obtain the lithium alloy. However, if the negative electrode substrate or the outer case is alloyed with lithium by using a lithium alloy partner metal, it is necessary to leave the negative electrode part and remove the other parts so that only the negative electrode part is alloyed with lithium. After masking, the negative electrode part is energized in an organic solvent in which lithium salt is dissolved, for example, using lithium metal as the counter electrode. [A method of alloying lithium using an electrochemical method such as controlling the degree of alloying with ffi can be suitably employed.

The positive electrode active material of the battery of the present invention may be any ordinary battery positive electrode active material, for example, 102°CI"z03.V.
2O5, VeO+3. Mn02cuo, Mn0z, C
Gold RW such as LI5 V201 o! compound, Ti 82
, Fe S, CLI Co 84.

Metal sulfides such as MO33, graphite which can be doped with anion A, polyaniline, polyacetylene, poly-p-phenylene, polybenzene, polypyridine, polythiophene, polyfuran, polypyrrole, anthracene, naphthalene, etc., and these. Derivatives of organic 5
Among them, when an organic conductive polymer material such as polyaniline is used as a positive electrode active material, the organic conductive polymer material is lightweight and has excellent flexibility compared to other positive electrode active materials. Polyaniline is particularly preferred as a positive electrode active material for lightweight and small batteries because it is easy to mold, and polyaniline can be obtained with good adhesion to substrates such as metals and carbon molded bodies by electrochemical polymerization. Furthermore, the composite of these substrates and polyaniline can be used as is as a positive electrode active material for batteries because the polyaniline can be used as a positive electrode and the substrate can be used as a positive electrode current collector and a container.

Note that there is no particular restriction on the form of the positive electrode substrate, and it can be used in various forms such as fiber, cloth, nonwoven fabric, film, plate, and powder. For example, when the positive electrode active material is graphite, carbon fiber, carbon cloth, carbon nonwoven fabric, carbon vapor, carbon foil, carbon foam, carbon powder, etc. can be used.

The liquid electrolyte and solid electrolyte described below can be used as the electrolyte constituting the battery of the present invention.

That is, the liquid electrolyte used in the battery of the present invention is usually an electrolyte solution in which an ionic compound is dissolved in a solvent, and the ionic compound constituting the electrolyte solution used in this battery is a combination of anion and lithium ion. An example of the anion is PFa −
, 5t) Fe −.

vA group elements (7) such as As Fs-, 5bC1s- (7)
) A halogenide anion, BF4-, AJ CJ4-
■Halide anions of △ group elements.

1-(Ia-), Br-, halogen anions such as CJ-, perchlorate anions such as 0.104-.

1” F2°−, CF 3S O3−, S CN −+
SO4-.

HSO4- etc. can be mentioned. Specific examples of compounds having these anions and lithium ions include Li PFa, L' 5bFs * Li AS F
8゜Li CjO4, Li (, Li Sr, li
C1゜Li BF4, Li AJCJa, LI
HF2.

Examples include Li SCN, Li 803 CF3, etc., but from the viewpoint of weight reduction and stabilization of the battery, lithium salts, especially Li CjO< and Li BF4 are preferred.

Lf PFs, Li I, Li Br, Li C
j etc. are preferably used.

Note that the solvent constituting the electrolyte solution of the battery is not particularly limited, but a relatively highly polar solvent is preferably used. Specifically, propylene carbonate, ethylene carbonate, benzonitrile, tetrahydrofuran, 2-methyltetrahydrofuran, γ-butylactone, dioxolane, methylene chloride, and triethyl phosphate.

Triethyl phosphite, dimethyl sulfate, dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, dioxane, dimethoxyethane, polyethylene glycol, sulforane.

One or a mixture of two or more organic solvents such as dichloroethane, chlorobenzene, nitrobenzene and the like can be mentioned.

Further, as the solid electrolyte used in the battery of the present invention, the above electrolyte solution is impregnated with a polymer such as polyethylene oxide, polypropylene oxide, an isocyanate crosslinked product of polyethylene oxide, or a phosphazene polymer having an ethylene oxide oligomer in the side chain. Organic solid electrolyte, Li 3 N, Li BCl2. Li4
Examples include inorganic solid electrolytes such as lithium glass such as SiO<-1i3B03.

In addition, when interposing an electrolyte in the battery of the present invention, if the electrolyte used is a solid electrolyte, there is no risk of contact between the positive and negative electrodes, and the solid snow melt can be directly interposed between the positive and negative electrodes. However, when the electrolyte used is a liquid electrolyte, contact between the positive and negative electrodes (-) may occur, so it is preferable to interpose a separator between the positive and negative electrodes to prevent short-circuiting of current due to contact between the two electrodes.As a separator. Porous materials capable of passing or containing the electrolyte, such as nonwoven fabrics, woven fabrics, and nets made of synthetic resins such as polytetrafluoroethylene, polypropylene, and polyethylene, can be used.

The battery of the present invention can be used as batteries of various shapes such as cylindrical shape, button shape, coin shape, film shape, etc., and batteries of various sizes can be formed. By integrating these, a thin battery can be constructed.

11 Sad LL As explained above, TF111 of the present invention! ! By integrating the negative electrode and the outer can, the battery can be made smaller and thinner, and the battery assembly process can be simplified. There is no peeling between the battery and the outer can, making it possible to lower the internal resistance of the battery, and by using a lithium alloy as the negative electrode active material, the battery has a long life and high energy density. When configured as a secondary battery, it can be endowed with features such as exhibiting excellent charging and discharging characteristics, making it suitable for use in a wide variety of applications such as automobiles, airplanes, vortaple machines, computers, and electric vehicles. It is something.

(Example) A disc-shaped aluminum substrate having a diameter of 1 CTl+1 and a thickness of 200 μm was joined to the inside of a stainless steel exterior can by spot welding. Next, the outer periphery of this disc-shaped aluminum base is masked with an insulating material, the disc-shaped aluminum part of this aluminum base/casing integrated body is used as a working electrode, lithium metal is used as a counter electrode, and 11IIO1/J is used as an electrolyte. LiC
Using a propylene carbonate solution of O04, Pi
The aluminum substrate was electrolyzed at 40IllAH to form a lithium alloy, and a disk-shaped lithium-aluminum alloy was electrochemically produced.

The outer can thus obtained is integrally bonded with lithium-ion
In addition to using aluminum/nium alloy as the negative electrode,
A positive electrode of 1.5 CIIlφ was formed using polyaniline as a positive electrode active material, a propylene carbonate solution of 1 m0J/1 iBF4 was used as the electrolyte, polypropylene paper was used as the separator, and the outer can on the positive electrode side was sealed using a polypropylene gasket. A coin-type battery with a thickness of 1.6 m was constructed.

The polyaniline used was 1.5 moj/J
Aniline monomer, 3, □ao4/, 1 HB
It was obtained by electrolytic polymerization on a platinum plate in an aqueous solution containing Fa.

Charge the coin-type battery with the above configuration for 8 hours at 0.5 mA until it becomes 2.0 ■.
Charging and discharging is performed as one cycle of charging and discharging electricity,
The internal low count for each cycle was determined.

As a result of this measurement, the internal resistance was approximately 400, and this value hardly changed even after 20 cycles of invasion.

[Comparative example]

A coin-type battery was obtained in the same manner as in the example except that aluminum was not integrated into the outer can in constructing the coin-type battery, but instead an electrochemically produced lithium-aluminum alloy was brought into contact with the outer can. This coin-shaped battery was charged and discharged in the same manner as in the example, and the internal resistance was measured for each cycle.

As a result of this measurement, the internal resistance at the initial stage of charging and discharging was approximately 800, and after 10 cycles, it rapidly increased to 150-400.
00Ω, and disturbances thought to be due to poor contact were observed in the discharge curve.

From the results of the above-mentioned actual cases and comparative examples, it is clear that the outer can of the present invention and 1
A battery using a lithium alloy as a negative electrode active material has a negative ti m
Compared to a case where the body and the outer can are not integrated, the internal resistance of the battery is sufficiently low, and the product of the present invention is more stable as a secondary battery with less internal resistance change due to repeated charging and discharging. This was found, and the effects of the present invention were confirmed.

Claims (1)

[Claims] 1. A battery characterized in that the negative electrode and the outer case are integrally formed, and a lithium alloy is used as the negative electrode active material.