JPH07107862B2 - Polyaniline battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a polyaniline battery using polyaniline as a positive electrode, lithium or a lithium alloy as a negative electrode, and a nonaqueous organic electrolytic solution as an electrolytic solution.

[Conventional technology]

In general, a polyaniline battery has a property that polyaniline exhibits conductivity due to ion doping. Therefore, by using this polyaniline as a positive electrode active material, a change in the electrode potential due to a change in the doping amount in the conductor region is prevented. It is designed to be used and can function as a secondary battery.

By the way, in the conventional polyaniline battery, austenitic stainless steel such as SUS304 and SUS316 and SUS430 based ferrite stainless steel are used as the material of the current collector such as the positive electrode can and the negative electrode can. A liquid in which LiClO ₄ is dissolved as an electrolyte in a non-aqueous organic solvent is widely used (unknown literature).

However, the polyaniline battery using a non-aqueous organic electrolyte solution containing LiClO ₄ above, the high oxidizing LiClO _4, risk causing fire or explosion if there has been a such overdischarge Gyotsu or accident or misuse However, there is a problem in that the organic solvent of the electrolytic solution is oxidized and the battery characteristics are deteriorated.
For this reason, recently, LiClO ₄ was replaced with Li as an electrolyte.
The use of fluorine-containing lithium salts such as BF ₄ and LiPF ₆ is being considered.

[Problems to be Solved by the Invention]

However, in the electrolytic solution using the above-mentioned lithium fluoride-containing salt, there is no risk of the above-mentioned danger or the oxidation of the organic solvent, but on the other hand, it does not have an oxidizing action. When voltage discharge or charge / discharge is repeated,
The oxide protective film, which is usually present on the surface of the current collector made of stainless steel in contact with the positive electrode, is easily damaged to cause pitting corrosion, and the progress of this corrosion causes the eluted stainless steel component to be deposited on the negative electrode surface. As a result of promoting self-discharge due to an internal short circuit, the durability of the battery is reduced and the service life is shortened.

In view of the above-mentioned circumstances, the present invention does not have a problem of internal short circuit due to corrosion of the positive electrode current collector surface even when using a fluorine-containing lithium salt as an electrolyte of an electrolytic solution, and thus has safety and durability. The purpose is to provide a superior polyaniline battery.

[Means for Solving the Problems]

As a result of intensive studies to achieve the above-mentioned object, the present inventors have constructed a ferrite composition stainless steel of a specific composition in place of at least the contact portion of the positive electrode current collector with the conventional general-purpose stainless steel. In this case, this stainless steel exhibits excellent corrosion resistance, and even if high voltage discharge is performed or charge / discharge is repeated in a battery configuration using a lithium salt containing fluorine as the electrolyte of the electrolytic solution, a current collector. It was found that the internal short circuit due to the corrosion of the battery was largely suppressed, the durability of the battery was remarkably improved and the battery had a long life, and the present invention was accomplished.

That is, the present invention is a polyaniline battery using polyaniline as a positive electrode, lithium or a lithium alloy as a negative electrode, and a non-aqueous organic electrolytic solution as an electrolytic solution, in which at least the contact portion of the positive electrode current collector with the positive electrode contains Cr of 18 to 20% by weight, 1.75 to 2.25% by weight of Mo, 0.3 to 1.0% by weight of Ti and Nb, and 0.02% by weight or less of C and N, respectively, and composed of ferritic stainless steel. The present invention relates to a polyaniline battery characterized by:

Further, in the present invention, a preferred embodiment is a configuration in which the above-mentioned non-aqueous organic electrolytic solution is obtained by dissolving a fluorine-containing lithium salt.

[Constitution / Operation of Invention]

In the polyaniline battery of the present invention, as a material forming at least a contact portion of the positive electrode current collector with the positive electrode, as described above.
Ferrite stainless steel with a specific composition containing 18 to 20% by weight of Cr, 1.75 to 2.25% by weight of Mo, 0.3 to 10% by weight of Ti and Nb in total, and 0.02% by weight of C and N, respectively. Since steel (hereinafter referred to as high corrosion resistance ferritic stainless steel) is used, even when a non-aqueous organic electrolytic solution that does not have an oxidizing action, such as an electrolytic solution containing a lithium salt containing fluorine, is used. The internal short circuit due to corrosion of the positive electrode current collector is unlikely to occur, and excellent durability is exhibited.

It is not clear why the high corrosion resistant ferrite stainless steel has a very high corrosion resistance inside the battery as compared with the general-purpose stainless steel that has been conventionally used for the current collector of this type of battery, Ti and Nb contained in the above specified amount
Due to the fact that it greatly contributes as a corrosion resistance-imparting component in the Fe-Cr-Mo composition and that the C and N components that react with Cr and cause grain boundary corrosion due to the lack of Cr at the crystal grain boundaries are extremely small, It is assumed that corrosion elution is unlikely to proceed even if the oxidation protection film on the surface is damaged by repeated high-voltage discharge and charge / discharge.

In the present invention, at least the contact portion of the positive electrode current collector with the positive electrode may be made of the above-described highly corrosion-resistant ferrite stainless steel. For example, in a button type or coin type battery configuration, the positive electrode current collector is used. In addition to using the stainless steel as the positive electrode terminal plate (positive electrode can) itself, a foil or thin plate made of highly corrosion-resistant ferrite stainless steel is arranged on the inner surface side of a conventional general-purpose stainless steel positive electrode terminal plate, or A crimped configuration can also be adopted.

In the case where a positive electrode made of polyaniline is provided with a collector network or a sheet having a polyaniline layer deposited on the net-like electrode by an electrolytic oxidation polymerization method is used as the positive electrode, the above collector and net-like electrode are used. It is desirable to use the above-mentioned high corrosion resistance ferritic stainless steel as the material.

On the other hand, for the negative electrode current collector, the above-mentioned high corrosion-resistant ferrite stainless steel can be used, but in terms of cost, it is the same as the conventional one.
It is preferable to use general-purpose stainless steel such as austenitic stainless steel such as SUS304 and SUS316, or ferrite stainless steel such as SUS304.

As the positive electrode of the battery of the present invention, a polyaniline powder synthesized by a chemical oxidative polymerization method, an electrolytic oxidative polymerization method, or the like, or a compression molded body of a powder obtained by adding a conductive auxiliary agent such as a carbon powder to the polyaniline powder, and the above net-shaped electrode A sheet having a polyaniline layer deposited thereon is used. Lithium or a lithium alloy is used as the negative electrode, and the lithium alloy here includes not only a metallurgical alloy but also a lithium foil and another metal foil such as aluminum which is pressure-bonded and integrated.

As the non-aqueous organic electrolytic solution, a lithium ion conductive electrolytic solution obtained by dissolving a lithium salt as an electrolyte in a non-aqueous organic solvent such as propion carbonate, γ-butyrolactone, dimethoxyethane, dioxolane is preferably used. .

The lithium salt of the electrolyte is not particularly limited, but a fluorine-containing lithium salt such as LiBF ₄ , LiPF ₆ , LiCF ₃ SO ₃ is suitable. That is, these fluorine-containing lithium salts have the advantage that they do not have the danger of oxidizing LiClO ₄ or an organic solvent, and that the electrolytic solution containing them has a relatively high electrical conductivity. Since the difficulty of corrosion of the positive electrode current collector due to having no action is eliminated by the use of the above-mentioned highly corrosion-resistant ferrite stainless steel,
The application effect of the present invention is particularly great.

FIG. 1 and FIG. 2 each show a structural example of the polyaniline battery of the present invention applied to a button type battery.

In the battery A shown in FIG. 1, the dish-shaped positive electrode terminal plate 1 made of the above-described highly corrosion-resistant ferrite stainless steel and the dish-shaped negative electrode terminal plate 2 made of general-purpose stainless steel are opposed to each other, and the peripheral portions of both are synthesized. A flat airtight container is formed by fitting and press-fitting the annular gasket 3 made of an elastic insulating material such as rubber or synthetic resin. Inside the sealed container, a positive electrode 5 made of polyaniline bonded to the positive electrode terminal plate 1, a negative electrode 6 made of lithium or a lithium alloy bonded to the negative electrode terminal plate 2 via a current collecting network 4 such as a stainless net, and both electrodes A separator 7 made of a porous insulating material such as polypropylene non-woven fabric interposed between 5 and 6 is loaded while being immersed in the non-aqueous organic electrolytic solution.

On the other hand, in the battery B of FIG. 2, except that a positive electrode terminal plate 11 made of general-purpose stainless steel is used and the foil 12 of the high corrosion-resistant ferrite stainless steel is arranged on the inner surface side thereof. , The same as battery A in FIG.
The same parts as those in the figure are designated by the same reference numerals.

The present invention is not limited to the button type battery shown in the figure, but can be applied to polyaniline / lithium secondary batteries of various forms and structures.

〔The invention's effect〕

According to the present invention, since at least a portion of the positive electrode current collector that is in contact with the positive electrode is made of highly corrosion-resistant ferrite stainless steel having a specific composition, the positive electrode current collector can be used even when repeated high voltage discharge or charge / discharge is performed. It is possible to provide a polyaniline battery having excellent durability and long life, which is unlikely to cause self-discharge due to an internal short circuit due to corrosion elution of the body.

Further, when a fluorine-containing lithium salt is used as the electrolyte of the non-aqueous organic electrolytic solution in the polyaniline battery, there is an advantage that the danger of ignition and explosion is eliminated, and excellent durability and battery characteristics are obtained.

〔Example〕

 Hereinafter, examples of the present invention will be specifically described.

Example 1 Aniline was added to an aqueous solution in which 2 mol / concentration of HBF ₄ was dissolved.
It is dissolved at a ratio of mol / mol, and K _{2 is} added as an oxidant in this solution.
Cr ₂ O ₇ was added in an amount of 0.2 mol / mol, the polymerization reaction was carried out at 20 ° C. for 1 hour, the reaction solution after polymerization was filtered, and the obtained polymerization product was thoroughly washed with water and then at 100 ° C. Vacuum drying was performed to obtain a polyaniline powder having an average particle diameter of 0.25 μm.

This polyaniline powder (50 mg) was filled in all the molds and compression-molded by a conventional method to prepare pellet-shaped compacts having a diameter of 15 mm and a thickness of 0.35 mm.

Next, the positive electrode terminal plate has a composition of 19 wt% Cr, 2.05 wt% Mo, 0.3 wt% Ti, 0.5 wt% Nb, 0.008 wt% C, 0.0092 wt% N, and the balance Fe. Made of ferrite stainless steel, SU as negative electrode terminal plate
S430, molded product as positive electrode, thickness as negative electrode
Li-Al alloy with a diameter of 15 mm formed by crimping 0.15 mm lithium foil and 0.2 mm thick aluminum foil, a 0.13 mm thick sheet made of polypropylene nonwoven fabric as a separator, and propylene carbonate and 1.2 as an electrolyte. LiBF ₄ dried in a mixed solvent of 1: 1 by volume with dimethoxyethane
A button type polyaniline battery A having a structure shown in FIG. 1 was prepared by using each of the non-aqueous organic electrolytic solutions prepared by dissolving 1 at a concentration of 1 mol / concentration.

Example 2 While using a positive electrode terminal plate made of SUS430,
Between the positive electrode terminal plate and the positive electrode made of polyaniline,
A button-shaped polyaniline having the structure shown in FIG. 2 was prepared in the same manner as in Example 1 except that a 20 μm thick foil made of ferrite stainless steel having the same composition as the positive electrode terminal plate of Example 1 was arranged in a dish shape. Battery B was produced.

Comparative Example A button type polyaniline battery C was produced in the same manner as in Example 2 except that a foil made of ferrite stainless steel was not used.

For each of the above polyaniline batteries A, B, C, 60 ℃
In, at 3.0V, 3.3V, 3.5V, 3.7V constant voltage, after 20 days of floating, open circuit voltage was measured and the preservability of charge and discharge performance was examined. was gotten. In addition, this storability is measured by measuring the battery capacity by performing a charge / discharge test with a charge end voltage of 3.3 V, a discharge end voltage of 2.0 V, and a charge / discharge current of 0.5 mA after the above floating.
This measured value was shown as a ratio (%) to the initial capacity before floating.

From the results in the above table, it is understood that in the battery C having the conventional structure, the open circuit voltage and the battery capacity after the floating are significantly reduced as the floating voltage is increased, and the durability is problematic. On the other hand, in the batteries A and B of the present invention, it is clear that even if the floating voltage is increased, the open circuit voltage and the battery capacity are reduced very little and the durability is excellent and the life is long.

For these batteries A, B, C, the above 3.5V and 3.7
After disassembling the battery after floating V, batteries A and B
However, black deposits were observed on the separator in Battery C, and it was confirmed by fluorescent X-ray analysis that the deposits were stainless steel component deposits. From this, in the battery C having the conventional configuration, pitting corrosion occurs on the inner surface of the positive electrode terminal plate due to high-voltage discharge, and the eluted stainless steel component is deposited on the negative electrode side and penetrates the separator, resulting in an internal short circuit. It can be seen that self-discharge is promoted and durability is deteriorated.

[Brief description of drawings]

1 and 2 are vertical cross-sectional views showing a structural example of the polyaniline battery of the present invention. 1, 11 …… Positive electrode terminal plate (positive electrode current collector), 2 …… Negative electrode terminal plate, 5 …… Positive electrode, 6 …… Negative electrode, 7 …… Separator, 12…
… Foil (positive electrode current collector)

Claims (2)

[Claims] 1. A polyaniline battery using polyaniline as a positive electrode and lithium or a lithium alloy as a negative electrode and a non-aqueous organic electrolytic solution as an electrolytic solution, wherein at least a contact portion of the positive electrode current collector with the positive electrode contains 18 to 20 Cr. Wt%, Mo 1.
Polyaniline containing 75 to 2.25% by weight, 0.3 to 1.0% by weight of Ti and Nb in a total amount, and 0.02% by weight or less of C and N, respectively, made of ferritic stainless steel. battery. 2. The polyaniline battery according to claim 1, wherein the non-aqueous organic electrolytic solution comprises a solution containing a fluorine-containing lithium salt as an electrolyte.