JPS62295370A - Electric cell - Google Patents

Abstract

PURPOSE:To prevent a sudden increase of the inner resistance during the operation, by fixing a negative electrode consisting of lithium or a lithium alloy to armoring cans through collectors, and securing the electrical connection between the negative electrode and the armoring cans. CONSTITUTION:As a negative electrode active substance, lithium or a lithium alloy is used. In this case, there is no restriction on the type of the lithium alloy, but an alloy of aluminum and lithium is especially preferable to have a good negative electrode property and a good plastic performance. Moreover, the negative electrode 4 is fixed to armoring cans 1a and 1b through collectors 6 and 9. In this case, there is no restriction on the material of the collectors 6 and 9, and an adequate form of stainless steel, nickel, aluminum, platinum, and carbonic conductor, for example, are available for this purpose, a stainless steel being especially preferable. Since a cell with the negative electrode of lithium or a lithium alloy has a high voltage, and a high energy density with little self-discharge, the stainless steel is preferable to be thin, being 5 to 100mum normally.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention The present invention relates to a battery using lithium or a lithium alloy as a negative electrode active material. The present invention relates to a battery that has stable electrical connection, such as no increase in energy consumption and therefore excellent cycle life even when used as a secondary battery.

lil 3f that 54 years old technology and ° Ming try to solve
Batteries using ir, i lithium or lithium alloys as negative electrode active materials are attracting attention as long-life, high-energy-density batteries, especially secondary batteries with excellent charge-discharge characteristics, due to their ability to achieve high energy density. has been done.

However, in batteries using these lithium or lithium alloys as the negative electrode active material, the negative electrode and the outer can are prepared separately like other general batteries, and the negative electrode and the outer can are brought into sufficient electrical contact during battery assembly. However, 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.

On the other hand, in order to make sufficient electrical contact between the battery and the outer can, conventional methods have been adopted such as placing a current collector such as a mesh or a spring-like structural member between the electrode and the outer can. However, when lithium or lithium alloys are used as negative electrode active materials, they are brittle and may cause chips to occur in the negative electrode during battery manufacture, or may cause damage to the negative electrode and the outer case due to changes in the volume of the negative electrode during battery use. The electrical contact with the
The problem is that the internal resistance of the battery increases, and especially in the case of secondary batteries, as the battery is repeatedly charged and discharged, the internal resistance of the battery increases and the charging and discharging characteristics deteriorate, eventually making it impossible to charge and discharge. be.

The present invention was made in view of the above circumstances, and it prevents poor electrical contact with the outer can when lithium or lithium alloy is used as the negative electrode active material, and prevents the internal resistance from increasing rapidly during use. Therefore, it is an object of the present invention to provide a battery with high energy density and long life, which has a stable electrical connection over a long period of time, such as an excellent cycle life when used as a secondary battery.

To achieve the above object, the present invention includes a positive electrode, a negative electrode, and an electrolyte each housed in an outer can.

In a battery in which the negative electrode is made of lithium or a lithium alloy, the negative electrode is fixed to an outer can via a current collector.

According to the present invention, since the negative electrode made of lithium or lithium alloy is fixed to the outer can via the current collector,
This solves the problem of insufficient electrical connection between the negative electrode and the outer can, ensuring a stable electrical connection over a long period of time, preventing contact failures as much as possible, and reducing internal resistance during use. There is no sudden increase in the amount, and therefore a secondary battery with excellent cycle life can be obtained.

On the other hand, if the negative electrode made of lithium or lithium alloy and the outer can are directly fixed together by spot welding, for example, the strength of the welded part of the negative electrode decreases, and the negative electrode and the outer can become weaker when the number of charge/discharge cycles increases. Although there is a possibility that the battery will peel off and the battery life will be shortened, in the present invention, such a problem does not occur because the two are fixed together via a current collector.

The present invention will be explained in more detail below.

The battery of the present invention uses lithium or a lithium alloy as the negative electrode active material. In this case, there is no particular restriction on the type of lithium alloy; for example, alloys of lithium and one or more of aluminum, magnesium, indium, mercury, zinc, cadmium, lead, bismuth, tin, antimony, etc. are preferable. Although it can be used, it is particularly preferable to use an alloy with aluminum or lithium in terms of negative electrode characteristics and formability.

Further, in the present invention, the negative electrode is fixed to the outer can via a current collector. In this case, there are no limitations on the material of the current collector; for example, stainless steel, nickel, aluminum, or platinum in an appropriate shape.

Although a carbonaceous four-electric body or the like may be used, it is particularly preferable to use stainless steel.

Here, the type of stainless steel is not limited, and either austenitic or martensitic stainless steel can be used, but austenitic stainless steel is particularly preferable in terms of workability and corrosion resistance. Specifically, SUS 304, SUS
316 etc. can be suitably used. In addition, since batteries with lithium or lithium alloy as the negative electrode have high voltage and high energy density with little self-discharge, it is preferable that the stainless steel be thin.
It is suitable to set it as 100 microdays. On the other hand, 5p
If it is thinner, the strength will be weak and it may be difficult to bond with the negative electrode or the outer can, and if it is thicker than 100 capes, the utilization rate of the battery's internal volume will be low, resulting in insufficient performance as a high-density energy battery. Sometimes. Although there is no limitation on the shape of the stainless steel, it is particularly preferable to use a wire-like material, such as wire mesh, expanded metal, punched metal, or the like. Since such reticulated stainless steel is flexible and lightweight, it facilitates fixation of the negative electrode to the outer can, and is also advantageous in terms of making the battery lighter.

In the present invention, the means for fixing the negative electrode to the outer can via the current collector is not limited, and for example, a method of joining the negative electrode and the current collector, and the current collector and the outer can by adhesive, welding, or soldering, respectively. It can be adopted.

Welding methods are particularly preferred, especially spot welding methods.

The laser welding method and the TIG pulse welding method are suitable because they allow fine processing and can be applied to the formation of small batteries such as coin-type batteries and button-type batteries.

Note that when forming the negative electrode with a lithium alloy, the lithium alloy is brittle and may break during bonding, so after fixing a metal that can be alloyed with lithium, such as aluminum, to the outer can via stainless steel This metal can be alloyed with lithium by electrochemical methods.

As the positive electrode active material of the battery of the present invention, there is no problem with the positive electrode active material of ordinary batteries, such as TiO2, Cr, etc. .

■20stV, O,,,MnO,,CuO,MnO2,
Cu5V20. .

Metal oxides such as TiS, FeS, CuCo5.
, MoS, etc., as well as graphite that can be doped with anions, polyaniline, polyacetylene, poly-p-phenylene, polybenzene, polypyridine, polythiophene, polyfuran, polypyrrole,
Examples include polymers of anthracene, naphthalene, etc. and their derivatives, and other organic conductive materials. Among them, when an organic conductive polymer material such as polyaniline is used as a positive electrode active material, the organic conductive polymer material can be used as a positive electrode active material. Compared to active materials, polyaniline is particularly preferred as a positive electrode active material for lightweight and small batteries because it is lightweight, has excellent flexibility, and is easy to mold.
S, can be obtained with good adhesion to substrates such as carbon molded bodies, and the composite of these substrates and polyaniline can be used as is in batteries, with polyaniline as a positive electrode and the substrate as a positive electrode current collector or container. It can be suitably used as a positive electrode active material.

Furthermore, there is no particular restriction on the form of the positive electrode substrate; for example, Wi
It can be used in various forms such as fiber, cloth, non-woven fabric, film, plate, powder, etc. For example, when the positive electrode active material is graphite, carbon fiber, carbon cloth, carbon nonwoven fabric,
Carbon paper, carbon foil, carbon foam, carbon powder, etc. can be used.

In addition, when using an organic conductive polymer material as a positive electrode active material, this positive electrode can be fixed to the outer can directly or through a current collector in the same way as above, and this allows the organic conductive polymer material to be used as a positive electrode active material. When used as a positive electrode, electrical contact failure with the outer case is prevented, and internal resistance does not increase rapidly during use. Therefore, when used as a secondary battery, it has an excellent cycle life and can be used for a long time. It becomes possible to obtain a battery having stable electrical connection throughout.

In this case, from the viewpoint of electrical connection, it is preferable to integrate the organic conductive polymer material with the current collector, and to fix this current collector to the outer can. Here, as a method for integrating the organic conductive polymer material and the current collector, if the organic conductive polymer material is obtained in powder form by a chemical polymerization method, etc., the organic conductive polymer material in powder form can be A conductive polymer material is coated on a conductive substrate and compression molded, or a powder of an organic conductive polymer material is mixed with a binder, etc., made into a paste, and then applied onto a conductive substrate and dried. It can be manufactured by However, if such a powder is used, it may cause problems such as a decrease in the energy density of the battery, so an organic conductive polymer material is deposited on a conductive substrate using an electrolytic polymerization method. A method of doing so is preferred. When electrolytically polymerizing a conductive substrate as an electrolytic electrode in this way, an organic conductive polymer material is deposited on the conductive substrate in the form of a film, so by using this conductive substrate as an electrode current collector,
As mentioned above, battery electrodes will be manufactured at the same time as organic conductive polymer materials and J3 manufacturing, which is extremely advantageous in terms of manufacturing costs.Moreover, organic conductive polymer materials produced by electrolytic polymerization are Since it has a good electrical connection with the conductive substrate as a current collector, all organic conductive polymer materials can be effectively used as the active material for the top electrode, and the internal resistance is small. This has the advantage that the drop in voltage due to internal resistance is also small.

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

Namely, 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.9 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 PF5-+
SbF,-, AsF,-.

5bcQ, a halide anion of a group VA element such as -, a halide anion of a group IIIA element such as B F4-, AIICQ4-, r-(■a-LBr-+cQ-
Halogen anions such as, perchlorate anions such as CQ04-, HF2-, CFiSO,-, 5CN-, SQ,
-, H3O4-, and the like. Specific examples of compounds containing these anions and lithium ions include:

LiPF, Li5bFG, LiAsF, LiCQO
4, LiI.

LiBr, LiCLLiBF, , LiAfl (14, L
Examples include, but are not limited to, iHF2゜Li5CN, Li503CF, etc. Lithium salts, especially Lic
QO4eLiBF, ,LiPF, ,LiI,LiBr,
LiCQ or the like is 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-butyrolactone, dioxolane, methylene chloride, and triethyl phosphate.

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

One type or a mixture of two or more of organic solvents such as dichloroethane, chlorobenzene, and nitrobenzene 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, N, LiBCQ4. Li4Sin4. L.L., 80
Examples include inorganic solid electrolytes such as lithium glass such as No. 3 lithium glass.

1. 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 electrolyte can be directly interposed between the positive and negative electrodes. When the electrolyte to be used is a liquid electrolyte, there is a risk that the positive and negative electrodes may come into contact with each other, and it is preferable to interpose a separator between the positive and negative electrodes in order to prevent current short-circuiting due to contact between the two electrodes. As a separator, a porous material that can pass or contain the liquid, such as polytetrafluoroethylene.

Nonwoven fabrics, woven fabrics, nets, etc. made of synthetic resins such as polypropylene and polyethylene can be used.

The battery of the present invention has a cylindrical shape, a button shape, and a coin shape.

Film-shaped cylinders can be used as batteries of various shapes, and can form fu ponds of various sizes. However, according to the present invention, by fixing the negative rain and the outer can through the current collector, a battery with excellent reliability and a long life can be obtained.

As explained above, in the battery of the present invention, a stable electrical connection can be obtained by fixing the negative electrode and the outer can via the current collector, and it is possible to lower the internal resistance of the battery. In addition, by using a lithium alloy as the negative electrode active material, the battery has a long life and high energy density, and when used as a secondary battery, it has features such as excellent charge and discharge characteristics. Therefore, it is suitable for use in a wide variety of applications such as automobiles, airplanes, portable machines, computers, and electric vehicles.

EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples, but the present invention is not limited to the following Examples.

〔Example〕

Diameter 1■l! A circular stainless steel wire mesh (SUS
316,300 mesh) by sponoto welding, and the other side of this wire mesh was joined to the inside of the stainless steel exterior can by spot welding.Next, the outer periphery of this disc-shaped aluminum base was insulated. The disk-shaped aluminum adhered to the aluminum base/external can was used as a working electrode, lithium metal was used as a counter electrode, and a propylene carbonate solution of 1 mol/Q Li CQ O4 was used as an electrolyte, and one current was applied. The aluminum substrate was electrolyzed at 40 mAH to form a lithium alloy, and a disk-shaped lithium-aluminum alloy was electrochemically produced.

Using the lithium-aluminum alloy fixed to the thus obtained outer can via a current collector as a negative electrode,
Diameter 1.5a using 40cm polyaniline as positive electrode active material
A positive electrode with a thickness of 1.6 m was formed, a propylene carbonate solution of 1 mol/Q LiBF was used as the electrolyte, polypropylene paper was used as a separator, and the outer can on the positive electrode side was sealed using a polypropylene gasket. A coin-type battery was constructed. The polyaniline used was 1.5 mol/12 of 7-niline monomer, 3.0 mol/Q of 1-I monomer,
It was obtained by electrolytic polymerization on a platinum plate in an aqueous solution containing B F .

That is, this coin-type battery, as shown in FIGS. 1 and 2,
Exterior cans 1 each made of stainless steel
a and lb are fixed to each other via a gasket 2, and
A positive electrode 3, a negative electrode 4, and an insulating separator 5 which is interposed between these electrodes 3 and 4 and supports an electrolytic solution containing a dopant are housed in these outer cans 1a and 1b.

Further, 6 is a positive electrode current collector, and this current collector 6 uses the platinum plate that is the electrode during the electrolytic polymerization as it is, and is therefore closely integrated with the positive electrode 3 (polyaniline).
This current collector 6 is fixed to one of the outer cans 1a by spot welding 7 to the outer can 1a. Note that 8 is the negative electrode current collector made of the stainless steel mesh mentioned above.

The coin-type battery having the above configuration was charged and discharged, with a charging and discharging process of charging and discharging for 2 hours at Q, 5 mA as one cycle, and the internal resistance was measured for each cycle.

As a result of this measurement, the internal resistance was approximately 40Ω.

This value hardly changed even after 1000 cycles.

[Comparative Example 1] A coin-type battery was made in the same manner as in Example, except that aluminum was not fixed to the outer can and an electrochemically produced lithium-aluminum alloy was brought into contact with the outer can. A battery was obtained, and 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 80Ω, but after 10o cycles, it rapidly increased to 15Ω.
The resistance reached 0 to 400Ω, and there was a disturbance in the discharge curve of 61' fA, which was thought to be due to poor contact.

[Comparative Example 2] The same aluminum base as in the example was directly spot welded to the outer can, and then this base was made into a lithium alloy in the same process as in the example. Next, a coin type battery was obtained in the same manner as in the example except that this substrate was used as a negative electrode, and this coin type 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 40Ω, but after 400 cycles, it rapidly increased to 15Ω.
It reached 0 to 400Ω, and disturbances thought to be due to poor contact were observed in the discharge curve.

From the results of the above Examples and Comparative Examples, it is clear that a battery using the lithium alloy fixed via the outer can of the present invention and the current collector as the negative electrode active material has no negative electrode substrate even if the lithium alloy is used as the negative electrode active material. The internal resistance of the battery is sufficiently lower than when the battery is not fixed to the outer can or when it is directly fixed, 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. It was found that the effect of the present invention was confirmed.

[Brief explanation of drawings]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the battery of the present invention, and FIG. 2 is a cross-sectional view of essential parts taken along the line ■--■ in FIG. 1 a, 1 b...Exterior can, 3...Positive electrode, 4...
Negative electrode, 6.9... Current collector. Applicant Brideston Co., Ltd. Agent Patent Attorney Takashi Kojima Figure 1 Figure 2

Claims (1)

[Claims] 1. In a battery in which a positive electrode, a negative electrode, and an electrolyte are each housed in an outer can, and the negative electrode is made of lithium or a lithium alloy, the negative electrode is fixed to the outer can via a current collector. A battery characterized by: 2. The battery according to claim 1, wherein the current collector is made of stainless steel. 3. The battery according to claim 1 or 2, wherein the current collector is fixed to the negative electrode and the outer can by welding, respectively. 4. The battery according to any one of claims 1 to 3, wherein the positive electrode is fixed to the outer can directly or via a current collector. 5. The battery according to any one of claims 1 to 4, wherein the positive electrode is made of an organic conductive polymer material.