JPS63257180A - Secondary battery - Google Patents

Abstract

PURPOSE:To lengthen a life of charge and discharge cycles by using, as a separator, a combined material of polypropylene porous film and a polypropylene nonwoven fabric sheet containing glass fibers. CONSTITUTION:In the secondary battery provided with a positive electrode 3 and a negative electrode 5 made of a conductive high molecular material, nonaqueous electrolytic solution which lies between the positive electrode and the negative electrode, and a separator 7 which partitions off the positive and the negative electrodes, the separator 7 shall have a multilayered structure of polypropylene porous films A and polypropylene nonwoven fabric sheets B containing glass fibers. The separator 7 which is a combined material of polypropylene porous films A and polypropylene nonwoven fabric sheets B containing glass fibers is suited to a battery for which a positive electrode 3 of conductive high molecular material and nonaqueous electrolytic solution are used, and a battery with excellent characteristics in discharge capacity and cycle life length can be obtained. Thus this invention can be effectively utilized for small sized secondary batteries such as coin type or cylinder type secondary batteries.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a non-conductive material using an organic conductive polymer material such as polyaniline, which exhibits charging and discharging effects through doping, dedoping, intercalation, and deintercalation mechanisms, as a positive electrode. The present invention relates to a water secondary battery, and more specifically, to a secondary battery that is excellent in battery performance, particularly discharge capacity, energy density, and charge/discharge cycle life.

In recent years, there has been active research into secondary batteries that use materials that exhibit charging and discharging effects through doping, dedoping, intercalation, and deintercalation mechanisms as electrodes.
In addition, organic conductive polymer substances such as polyaniline are used as materials that exhibit these properties, and organic conductive polymer substances are used as electrodes of secondary batteries, especially positive electrodes, from the standpoint of reducing size and weight and improving flexibility. Various attempts to apply it are being considered. Among these organic conductive polymer substances, polyaniline is known to be particularly excellent in charge and discharge capacity as an electrode material for secondary batteries, and can constitute a secondary battery with excellent cycle life.

On the other hand, lithium alloys are used as negative electrode materials for secondary batteries because they can be repeatedly charged and discharged, have excellent battery performance such as high energy density and high discharge potential, and can be made smaller and lighter. This has attracted much attention, and efforts are being made to put a secondary battery into practical use that uses a conductive polymer material such as polyaniline as a positive electrode and a lithium alloy as a negative electrode.

Such secondary batteries can be configured in various shapes such as cylindrical, button-shaped, box-shaped, oval, etc., but when manufacturing such secondary batteries, it is necessary to interpose a non-aqueous electrolyte between the positive and negative electrodes. At the same time, a separator (diaphragm) is provided between these positive and negative electrodes.

Conventionally, this separator has three types: (1) a type that uses only one or more sheets of polypropylene nonwoven fabric, (2) a type that uses one layer of polypropylene nonwoven fabric and one polypropylene porous membrane, and (2) a type that uses a polypropylene porous membrane. Types that use one or more polypropylene porous membranes interposed between two polypropylene nonwoven fabrics are known. Polypropylene nonwoven fabric is widely used as a material for separators.

However, conventional separators that use a polypropylene nonwoven fabric or a polypropylene porous membrane alone or a combination of these are used.

When constructing a non-aqueous secondary battery using an R-electrolytic polymer material as a positive electrode, its cycle life is not necessarily sufficient, and it has been desired to extend the cycle life of the secondary battery.

The present invention was made in view of the above circumstances, and is intended to prevent doping, dedoping, and intercalation.

Even when forming a small secondary battery such as a coin-shaped or cylindrical secondary battery by using an organic conductive polymer material such as polyaniline as an electrode material that exhibits charging and discharging effects through a deintercalation mechanism as a positive electrode, It is an object of the present invention to provide a non-aqueous secondary battery that has sufficient discharge capacity and energy density and has an excellent charge/discharge cycle life.

The present inventors have conducted intensive studies on improving the charge/discharge cycle life of non-aqueous secondary batteries using conductive polymer materials such as polyaniline for the positive electrode. discovered that the separator used in this type of secondary battery has a significant effect on the cycle life, and by combining a porous polypropylene membrane and a polypropylene nonwoven fabric containing glass fiber as the separator, It was found that the charge/discharge cycle life was improved.

That is, as shown in Examples and Comparative Examples to be described later, conventional polypropylene nonwoven fabrics are used as separators, glass fiber-containing polypropylene nonwoven fabrics or polypropylene porous membranes are used alone, and even simple Although a sufficiently stable cycle life has not been achieved even when a glass fiber membrane is combined with a porous polypropylene membrane, when combining a glass fiber-containing polypropylene nonwoven fabric with a porous polypropylene membrane, The inventors have discovered that even if the electrolyte is non-aqueous, the electrolyte can be sufficiently retained, the battery capacity can be increased, and the cycle life can be extended, and the present invention has been developed.

Therefore, one aspect of the present invention is to provide a positive electrode made of a conductive polymer material;
A secondary battery comprising a negative electrode, a non-aqueous electrolyte interposed between these positive and negative electrodes, and a separator that partitions between these positive and negative electrodes, wherein the separator includes a porous polypropylene membrane and a polypropylene nonwoven fabric containing glass fiber. The object of the present invention is to provide a secondary battery characterized in that it has a laminated structure.

The present invention will be explained in more detail below.

An example of the organic conductive polymer material used in the positive electrode of the secondary battery of the present invention is polyacetylene.

Polymers of benzene and its derivatives such as polybenzene, polyparaphenylene, polyaniline, polypyridine, polythiophene, polyfuran, polypyrrole, and polymers of hetero or polynuclear aromatic compounds such as anthracene and naphthalene are used as electrode active materials. There is no limit to the type of things you can get. Among them, polyaniline, especially polyaniline obtained by electrolytic oxidation polymerization method.

During electrolytic oxidation polymerization, this polyaniline is deposited and formed with good adhesion to the anode substrate, and the anode substrate can be used as a current collector or container for battery electrodes.Not only can the battery manufacturing process be simplified, but this polyaniline can also be used as an electrode. The secondary battery used as the active material has characteristics such as being able to reduce internal resistance and improving Coulombic efficiency, and therefore can be suitably used as the positive electrode of the secondary battery of the present invention.

In this case, the polyaniline usually has an aniline concentration of 0.
01-5 mol/n, especially 0.5-3 mol/Q and acid concentration 0.02-10 mol/Q, especially 1-
Particularly suitable is one obtained by electrolytically polymerizing an electrolytic solution containing 6 mol/Q. The acids used in the electrolytic solution for the electrolytic polymerization are not particularly limited, but include hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid, perchloric acid, hydrofluoroboric acid, phosphoric acid, acetic acid, etc. Among them, hydrochloric acid, Perchloric acid, fluoroboric acid, etc. are preferred, and the temperature of the electrolyte is between 15 and 3
The range of 0'C is preferable in terms of the production rate of polyaniline, and in particular, the temperature of 20°C or less improves the film forming properties of polyaniline, making it even more suitable for use as the electrode active material of the secondary battery of the present invention. The polyaniline obtained is what is obtained.

Furthermore, although there is no particular restriction on the negative electrode of the secondary battery of the present invention, a lithium alloy is preferably used. The lithium alloy is made by heating and melting lithium in an alloy of one or more metals such as aluminum, silver, lead, tin, bismuth, antimony, indium, and cadmium that can be alloyed with lithium in a vacuum or an inert gas atmosphere. Manufactured by a method of homogeneously mixing, cooling and solidifying to form an alloy.

Any material produced by a method of electrochemically introducing lithium can be used. There are no particular restrictions on the synthetic composition of the lithium alloy, the amount of negative electrode active material, etc., but the types of lithium alloys include the above-mentioned Li-AQ alloy, Li-
AM-In alloy, LL-kQ-Bi gold alloy are suitable;
Particularly preferred is Li-Af1 alloy.

In addition, when polyaniline is used for the positive electrode, the effective lithium concentration in the negative electrode active material, which performs electrochemical intercalation and desorption during charging and discharging of the secondary battery, per 1 g of polyaniline as the positive electrode active material. is 4X10-3 mol-1
Preferably, the amount is 0.times.10" moles.

Furthermore, the electrolyte of the non-aqueous electrolyte constituting the secondary battery of the present invention, that is, the compound that generates ions that can be occluded in the positive and negative electrodes, is a compound consisting of a combination of an anion and a cation, and examples of the anion include: is PFG-, SbF
, ``y A S F g -x S b CQs-, the halide anion of the VAM source, BF4-, A
I [[Halide anion of group A element, ■'''' (3 I) such as ΩCQ4□.

B(, halogen anion such as CQ-, perchlorate anion such as CQo4, HF, =, cF3so3-.5cN
-, o knee.

Examples of cations include HS O4''', etc. Examples of cations include alkali metal ions such as Li◆, Na◆, and ◆.Specifically, LiP F
,.

L I S b F 6 g L I A S F 6
p L I CQ O4g L I I + L I
B r HL I CQ ■ NaPF@vNaSbF@gNaAsF@INaCQO
4gNaIgKPF@yK S b FG # K
A 8 F @ g K CQ O4HL I B F
4 g L I A Q CQ4 gLiHF,,L
Examples include i5CN, KSCN, Li5O, CF3, etc., but are not limited to these, but from the viewpoint of weight reduction and stabilization of secondary batteries, lithium salts, especially LiC
Qo, , LiBF, , LiPF5 are suitable.

The above-mentioned electrolyte is usually used in a state dissolved in a solvent, and in this case, the solvent is not particularly limited, but a relatively polar solvent is preferably used. Specifically, propylene carbonate, ethylene carbonate, benzonitrile, and acetonitrile.

Tetrahydrofuran, 2-methyltetrahydrofuran,
γ-butyrolactone, dioxolane, methylene chloride, triethyl phosphate, triethyl phosphite,
Dimethyl sulfate, dimethylformamide, dimethylacetamide, dimethyl sulfoxide, dioxane, dimethoxyethane, polyethylene glycol, sulfolane,
One or a mixture of two or more of dichloroethane, chlorobenzene, nitrobenzene and the like can be mentioned.

Among these, especially ethylene carbonate.

One type of solvent selected from propylene carbonate, dimethoxyethane, tetrahydrofuran, and γ-butyrolactone, or a mixed solvent formed by mixing two or more types of solvents is suitable.

Therefore, the secondary battery of the present invention has the above-mentioned positive and negative electrodes, a non-aqueous electrolyte interposed between these positive and negative electrodes, and a separator that partitions between these positive and negative electrodes, In this case, in the present invention, the separator has a laminated structure of two or more layers, and at least one layer is composed of a porous polypropylene membrane.

At least one of the remaining layers is composed of a nonwoven fabric made of polypropylene containing glass fibers.

Here, the polypropylene porous membrane is used to control the movement of lithium ions.

The pore diameter is preferably 50 m or less, more preferably 207 a or less. Due to such a small diameter, lithium can be smoothly deposited and dissolved on the lithium alloy, and the cycle life of the secondary battery can be improved. Note that the thickness of this porous membrane is not necessarily limited, but is preferably in the range of 25 to 100p.

On the other hand, glass fiber-containing polypropylene nonwoven fabric has excellent ability to retain the necessary electrolyte in batteries using conductive polymer materials, so it is effective in increasing capacity and cycle life. By combining the fiber-containing polypropylene nonwoven fabric with the polypropylene porous membrane, the cycle life of the secondary battery is significantly improved. On the other hand, when a polypropylene nonwoven fabric that does not contain glass fiber is used, it not only has poor performance due to its poor electrolyte retention ability, but also has low manufacturing strength, which reduces productivity. There is a problem that
It is not possible to sufficiently improve the cycle life of secondary batteries,
The purpose of the present invention cannot be achieved.

In this glass fiber-containing polypropylene nonwoven fabric,
From the standpoint of performance and manufacturing, it is preferable that the glass fiber content be 5 to 60% by weight. If the glass fiber content is less than 5%, the liquid retention property will be poor, whereas if it is 60% or more, there will be no problem in terms of the liquid retention property.

There are cases where the strength decreases and the water content increases, making it unsuitable as a non-aqueous electrolyte battery. In addition, the thickness of the glass fiber-containing polypropylene nonwoven fabric is preferably in the range of 50 to 200 Ia.

The lamination mode of the polypropylene porous membrane and the glass fiber-containing polypropylene nonwoven fabric is not particularly limited, and various modes are possible. For example, as shown in Fig. 1, a porous membrane A and a nonwoven fabric B are simply layered together, or as shown in Fig. 2, a porous membrane A is interposed between 8 layers B of two nonwoven fabrics. Examples include those with a sandwich structure.

As mentioned above, a separator that combines a porous polypropylene membrane and a nonwoven polypropylene fabric containing glass fibers is
A conductive polymer material is used for the positive electrode.

Suitable for batteries using non-aqueous electrolytes, it has high discharge capacity and excellent cycle life. Therefore.

The battery of the present invention is particularly effectively used as a small secondary battery such as a coin type or cylindrical secondary battery.

EXAMPLES Hereinafter, the present invention will be specifically explained by showing Examples and Comparative Examples, but the present invention is not limited to these Examples.

4. Dehydrated and vacuum-dried polyaniline obtained by electropolymerizing aniline. Omg was used as the positive electrode, a lithium-aluminum alloy was used as the negative electrode, and the electrolytic solution was an electrolytic solution containing LiBF4 dissolved in an equal volume mixed solvent of propylene carbonate and dimethoxyethane with an electrolyte concentration of 3 mol/42. The coin-type secondary battery shown in the figure was assembled and constructed in a humidity-controlled glove box. Here, in the coin type secondary battery shown in FIG. 3, 1a and lb in FIG.
is a container, 2 is a gasket, 3 is a positive electrode, and 4 is a positive electrode current collector.

5 is a negative electrode, 6 is a negative electrode current collector, and 7 is a separator, and this separator 7 is impregnated with an electrolyte.

The separator used was a two-layer structure consisting of a porous polypropylene membrane (50p thick) having a pore diameter of 20 mm and a polypropylene nonwoven fabric (120 mm thick) containing 40% by weight of glass fibers.

For comparison, the polypropylene porous membrane shown in Table 1,
A similar battery was manufactured by combining nonwoven fabrics to form a separator.

Next, this 'battery was charged with a current of 1 mA for 1 hour.

Thereafter, the battery was discharged at 1 mA for 1 hour, and its cycle characteristics were examined. The results are shown in Table 1. The results in Table 1 are for each 3
These are the results of the number of cycles performed on each battery and their average value.

From the results in Table 1, it is recognized that a secondary battery with excellent cycle life can be obtained by using a separator made of a combination of a polypropylene reticulated membrane and a glass fiber nonwoven fabric.

[Brief explanation of drawings]

FIGS. 1 and 2 are sectional views showing one example of a separator used in the present invention, and FIG. 3 is a schematic sectional view showing one embodiment of the present invention. 1 a, 1 b...container, 2... gasket, 3...
... Positive electrode, 4... Positive electrode current collector, 5... Negative electrode. 6... Negative electrode current collector, 7... Separator, A... Polypropylene porous membrane, B... Glass fiber-containing polypropylene nonwoven fabric. Applicant Brideston Co., Ltd. Agent Patent Attorney Takashi Kojima 1 Ito, °J Neichi sE Koto (spontaneous) June 30, 1985 Patent Application No. 91522 of 1988 2 Title of the invention Secondary Battery 3: Relationship with the case of the person making the amendment Patent applicant address: Mr. 10-1 Kyobashi-chome, Chuo-ku, Tokyo
Name (527) Representative of Brideston Co., Ltd.
House: 4th year of Showa, Agent: 104 Address: 5th floor, Dapa Create Building, 3-11-14 Ginza, Chuo-ku, Tokyo Phone: (545) 6454 7F
``Detailed Description of the Invention'' column. 6. Contents of amendment (1) In the 8th line of page 14 of the specification, "4.0■" is corrected to "r40■". that's all

Claims (1)

[Claims] 1. In a secondary battery comprising a positive electrode made of a conductive polymer material, a negative electrode, a non-aqueous electrolyte interposed between these positive and negative electrodes, and a separator that partitions between these positive and negative electrodes. . A secondary battery, wherein the separator has a structure in which a porous polypropylene membrane and a glass fiber-containing polypropylene book-bound woven fabric are laminated. 2. The secondary battery according to claim 1, wherein the conductive polymer material is polyaniline. 3. The secondary battery according to claim 1 or 2, wherein the negative electrode is a lithium alloy. 4. Claim 1, wherein the glass fiber content in the glass fiber-containing polypropylene nonwoven fabric is 5 to 60% by weight.
The secondary battery according to any one of Items 3 to 3.