JPS622469A - High-molecular secondary cell - Google Patents

Abstract

PURPOSE:To heighten the density of energy and lengthen life of rechargeability, by providing an active material made of anions in the main and contained in an electrolyte to be transferred between both electrodes. CONSTITUTION:A secondary cell comprises a positive and a negative electrodes and an electrolyte. The positive electrode is made of an electroconductive high- molecular substance. The negative electrode is made of a metal. In the charging of the cell, anions are released into the electrolyte from a metal salt produced on the negative electrode as a result of the combination of the metal, and the anions are taken from the electrolyte into the electroconductive high-molecular substance on the positive electrode. In the discharge of the cell, the anions taken into the electroconductive high-molecular substance are released into the electrolyte on the positive electrode to produce the metal and the salt. Since not a metal dissolving/educing reaction on the negative electrode but the transfer of the anions and the reaction with the metal are utilized, the metal for the negative electrode needs to be such that the solubility of the salt made of the metal and the anions is low. The electrolyte is a saturated one in which a salt of a metal of higher ionizability than that for the negative electrode is dissolved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a rechargeable secondary battery using a polymer compound as a positive electrode and a metal as a negative electrode.

[Background of the invention]

Polymers with conjugated type 2 compaction such as polyacetylene are
Electrochemically, anions such as Cl0a-, PF5-, BFa-, and L! It is known that p-type and n-type conductive polymers are created by doping with cations such as ``, (C4Hs)4N+.For example, The Chemical Society Op Japan Communication, 1979, pp. 594-595 ( 'l'he(:chemical
5ociety of Japan community
ation 1979 pp594-595).

Rechargeable batteries using such electrochemical doping have also been reported. As an example of this type of battery, polyacetylene membranes are used for the positive and negative electrodes, and propylene carbonate (C4HI)a NCl0a is used as the organic electrolyte.
In a battery using a dissolved material, the open circuit voltage is 25
It is reported that a short circuit current of 11.1 mA was obtained. The Chemical Society Op Japan Communication 1981, pp. 317-319 (
'l'chemical 5ociety of
Japan communication1981
See pp. 317-319).

Secondary batteries using polyacetylene as electrodes have recently been attracting attention because of their high energy density (Wh/Kq).

The types of batteries are (1) a battery that uses a conductive polymer for both electrodes, with anions at the positive electrode and cations at the negative electrode; (2) a battery that uses a conductive polymer for the positive electrode and a metal for the negative electrode; is a battery in which anions are taken in and taken out, and metal is dissolved and deposited at the negative electrode.

(3) A battery that uses a conductive polymer for both electrodes and moves one type of anion or cation; (4) A battery that uses a conductive polymer for the negative electrode, a compound for the positive electrode, and a battery that uses alkali metal ions, etc. A battery that takes in and out cations, (5) A battery that uses an intercalation compound in the negative electrode and a conductive polymer in the positive electrode, and takes in and out cations and anions in the negative electrode and the positive electrode, (6
) Batteries have been reported that use a conductive polymer for the negative electrode and an alkali metal for the positive electrode, allowing alkali metal ions to be taken in and taken out.

Among these batteries, batteries that take in and take out both anions and cations require a large amount of electrolyte and the energy density does not increase; However, due to the precipitation of resinous metals, problems such as battery short circuits occur, resulting in a short service life.

[Purpose of the invention]

An object of the present invention is to provide a rechargeable secondary battery with high energy density and long life.

[Summary of the invention]

The developed FiA uses a conductive polymer as the positive electrode material and a metal as the negative electrode material in a secondary battery consisting of a positive electrode, a negative electrode, and an electrolyte. is released into the electrolytic solution, and the anions in the electrolytic solution work to be incorporated into the conductive polymer at the positive electrode, while in the discharge process, the anions are incorporated into the conductive polymer at the positive electrode. This is a secondary battery that functions to release the anions contained in the electrolyte into the electrolyte solution and generate salt with the negative electrode metal.

Therefore, in the present invention, the generated metal salt is not substantially dissolved in the electrolytic solution.

The conductive polymer material used for the positive electrode of the secondary battery according to the present invention is mainly a polymer material having a conjugated 2]1 bond in the main chain, examples of which include polyacetylene, 7f!
Rehabilitation 5 Phenine, polythenylene, holipyrrole,
Many types of 4 are known, such as bokae anilene. Among these, anions such as (1) PF6-, S b
Fs-, As Pg''', 5bCt@-O halide anions of elements of the va group, ■) li such as BF2-
a-group halogenated anion, (3) do(Is'),
Br″″.

Halogen anions such as C1-, F-, (4) Ct0
Any material that can stably dope a perchlorate anion such as 4'''' or an oxyacid anion such as (5) S04''- may be used.

The solvent used only needs to be stable within the operating voltage of the battery.

In the present invention, the metal dissolution precipitation reaction at the negative electrode is not performed, but
In order to take advantage of the movement of anions and their reaction with metals, it is necessary to select metals used for the negative electrode that have a low degree of salt solubility with the above-mentioned anions. The electrolyte used is a saturated electrolyte in which a metal salt with a high ionization tendency (such as the metal used in the negative electrode) is dissolved.

In the secondary battery of the present invention, I! The active material that migrates between the electrodes is only the anion, and the amount of electrolyte is sufficient to moisten the electrode material space and the separator, such as a polymeric nonwoven fabric, necessary to prevent short circuits between the electrodes.

[Embodiments of the invention]

Hereinafter, the present invention will be further explained in detail with reference to examples of the present invention. 1 and 2 are enlarged perspective views and partially enlarged views of a secondary battery according to the present invention. Since a non-aqueous solvent is used for the electrolyte and a metal is used for the negative electrode, the outer wall of the battery case is thin! (1 to 100 μm) is covered with a laminated resin film l. Further, the structure of the polymer electrode 2 is such that a wire mesh 3 made of corrosion-resistant material is embedded therein in order to enhance the current collecting effect and take out the electrode terminal. A cloth-like sensor (4) made of polypropylene, glass, etc. is placed between the electrodes to prevent short circuits between the electrodes.The configuration diagrams in Figures 1 and 2 are of a single cell. It is also possible to stack the ponds by placing a suitable conductive separator between the cells to prevent electrolyte from moving between the cells.

Next, specific examples will be described.

Example 1 Polyacetylene was used for the positive electrode. The density of polyacetylene is 0.3 g/cm" and the thickness is ioo μm. A platinum wire mesh was used as the current collector. Propylene carbonate was used as the solvent.
Mg metal or Mg alloy was used for the negative electrode, and a saturated solution of magnesium chloride was used for the electrolyte.

The charge and discharge cycles were repeated under the conditions of a current density of 5 mA/cyf and a doping rate of chlorine ions to polyacetylene (molar ratio of chlorine ions per carbon atom) of 4 mo1%, and then the discharge end voltage was set to 0. The charge/discharge cycle life at 5 V was 400 times, and no resinous substance was observed to be deposited on the negative electrode.

Example 2 There was. A cycle test was conducted under the same charging and discharging conditions as in Example 1, and the cycle life was 520 times.

Also, the self-discharge rate was low at 91.7 units per day.

Example 3 Polythiophene was used for the positive electrode and Mg metal was used for the negative electrode. As the electrolytic solution, a 2 mol/l solution of lithium chloride in a mixed solvent of propylene carbonate and dimethoxyethane was used. A cycle test was conducted under the same charging and discharging conditions as in Example 1, and the cycle life at which the coulomb efficiency was 50 or more was 630 cycles.

For these Examples, as in Example 1, polyacetylene was used for the positive electrode, Mg metal was used for the negative electrode, and 1 mo
When a conventional secondary battery using a propylene carbonate solution containing l/l lithium perchlorate was subjected to a charge/discharge cycle test, Mg dendrites were deposited on the negative electrode after 100 cycles, and a short circuit occurred inside the battery. became the lifespan.

Example 4 A battery was assembled using polyaniline for the positive electrode and Mg metal for the negative electrode. The positive electrode polyaniline was electrolytically oxidized and polymerized from an acidic aqueous solution onto a platinum mesh, and after washing with water, it was vacuum dried at 80C before use. The electrolytic solution impregnated between the cell electrodes is a solvent prepared by mixing 1 to IK by volume of propylene carbonate and dimethoxyethane and saturated with lithium sulfate.

At a current density of 5 mA/cdl, the doping rate was 3 mmol/g for polyaniline, and the discharge end voltage was 0.
, 5V, the charge/discharge cycle life was 910 times. Moreover, the self-discharge rate under the same charging and discharging conditions was 1-7 days.

Example 5 Similar to Example 4, polyaniline was used for the positive electrode and Mg was used for the negative electrode.
-At alloy (atomic ratio of Mg/A=9) was used. The charge/discharge cycle life is 1200 times, and the self-discharge rate is l
It was 1/day.

For these examples, the same positive as Example 4 is applied.

Using a negative electrode material, the electrolyte contains 0.5 mol of lithium sulfate in a mixed solvent of propylene carbonate and dimethoxyethane.
A charge/discharge cycle test similar to that in Example 4 was performed on a conventional secondary battery using L-dissolved material, and the cycle life was 310 times, with Sυ and resinous Mg deposited on the negative electrode. It was done.

〔Effect of the invention〕

According to the present invention, in a secondary battery using a polymer having conjugated double viscosity in the main chain, a metal having low solubility in the polymer negative electrode is used as the positive electrode.

Maku,! By using a solution of a salt of a metal whose oxidation-reduction potential is more base than that of the negative electrode, a battery with a long charge-discharge cycle life can be provided because there is no resinous precipitation of the metal. Furthermore, since a saturated electrolyte containing a metal salt having a high ionization tendency is used, the resistance of the electrolyte can be lowered, and the energy density of the battery can be greatly improved.

[Brief explanation of drawings]

FIG. 1 is a partially sectional perspective view showing the structure of a secondary battery according to the present invention, and FIG. 2 is a partially enlarged sectional view thereof. ■...2 laminated resin film, 2... polyacetylene, 3... extracted band metal, 4... separator. 5... Negative electrode metal, 6... Electrode terminal.

Claims (1)

[Claims] 1. In a secondary battery comprising a positive electrode made of a conductive polymer material, a negative electrode made of a metal material, and an electrolytic solution interposed between the positive electrode and the negative electrode, A polymer secondary battery characterized in that the active material in the electrolytic solution that transfers mainly consists of anions only. 2. The polymer secondary battery according to claim 1, wherein the positive electrode is made of a polymer material having a conjugated double bond in its main chain. 3. The polymer secondary battery according to claims 1 and 2, wherein the negative electrode is made of Mg or an alloy thereof. 4. The polymer secondary battery according to claims 1, 2 and 3, characterized in that the electrolyte is a solution of a salt of a metal whose oxidation-reduction potential is more base than that of the negative electrode metal.