JPS61281458A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To enhance the charge/discharge capacity efficiency of a storage battery, by making at least one electrode of a mixture comprising an electroconductive polymer and a high-molecular electrolyte. CONSTITUTION:At least one electrode is made of a mixture comprising an electroconductive polymer and a high-molecular electrolyte. The polymer is powdered polyacetylene or the like. The high-molecular electrolyte is made of a polymer which has a special structure such as a spiral structure and a high molding property. For example, the high-molecular electrolyte is made of a composite material comprising a polymer such as polyethylene oxide, polymethyl methacrylate and polyvinyl pyrrolidone and a lithium salt such as lithium perchlorate and lithium borofluoride. Since the wetting property of the electrode to an electrolyte solution is enhance because of the presence of the high-molecular electrolyte, the charge/discharge capacity efficiency, cyclic property and preserving property of a storage battery are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Industrial Application Field The present invention relates to a non-aqueous electrolyte secondary battery that uses a conductive polymer as an electrode material.

c Port 1 Conventional technology Conventional non-aqueous electrolyte secondary batteries have a negative electrode made of a light metal such as lithium and molybdenum dioxide.

A positive electrode made of a metal compound such as vanadium pentoxide, and lithium perchlorate (LiC1!04) as an organic solvent.

It is composed of a non-aqueous electrolyte in which a solute such as lithium borofluoride (LiBF4) is dissolved.

And in recent years, 1, for example, JP-A-56-13646
As disclosed in Japanese Patent No. 9, a secondary battery using a conductive polymer typified by polyacetylene as an electrode material has been proposed.

Organic polymers usually exhibit little electrical conductivity, but
The conductive polymer used as the electrode material of this type of secondary battery has the characteristic that it can be doped, and its conductivity increases dramatically by doping. Furthermore, doping can also be performed electrochemically, and conductive polymers doped with anions can be used as positive electrodes of batteries, and conductive polymers doped with cations can be used as negative electrodes. By performing this reversibly, a battery that can be charged and discharged can be constructed.

Problems to be Solved by the Invention The present invention aims to improve the charge/discharge capacity efficiency, charge/discharge cycle characteristics, and storage characteristics of a non-aqueous electrolyte secondary battery that uses a conductive polymer as at least one electrode material. do.

In a battery using a conductive polymer electrode, in order to increase the capacity, it is necessary to increase the amount of conductive polymer in the battery. For this purpose, it is more advantageous to pressure-mold a powdered polymer to form a high-density electrode than to use a membrane-like polymer as the conductive polymer.

However, conductive polymers themselves generally do not have good moldability, and even if only conductive polymers are pressure molded, their mechanical strength is low, so the electrodes may collapse due to charge/discharge reactions or long-term storage, which may affect cycle characteristics or storage. There was a problem with the characteristics.

As a countermeasure against this, for example, a binder such as polytetrafluoroethylene is mixed.

If a binder is mixed, the capacity per unit volume inevitably decreases by that amount, and electrodes mixed with a fluororesin binder have poor wettability with the electrolyte, which has a negative impact on battery performance. will be given.

- Means for Solving the Problems The present invention relates to a non-aqueous electrolyte secondary battery using a conductive polymer electrode as at least one electrode.

It is characterized in that the conductive polymer electrode is made of a mixture of a conductive polymer and a polymer electrolyte.

The polymer electrolyte used here has a special structure and can be used as an electrolyte, and is a polymer with excellent moldability. Examples include those obtained by ion-exchanging an on-exchange resin with alkali ions.

A specific example of a bender is polyethylene oxide.

Complexes of polymers such as polymethyl methacrylate and polyvinylpyrrolidone and lithium salts such as lithium perchlorate and lithium borofluoride are known.

(E) Function In an electrode made of a mixture of a conductive polymer and a polymer electrolyte, the presence of the polymer electrolyte improves the wettability between the electrode and the electrolytic solution compared to when the current collecting polymer is used alone. Due to improved mechanical strength, charge/discharge capacity efficiency, cycle characteristics, and storage characteristics are improved.

(F) Example [Example 1] As a positive electrode, polyacetylene powder and polyethylene oxide were mixed at a weight ratio of 90:10.

This mixture was mixed with a diameter of 20.011. A disc-shaped product with a thickness of approximately 0.7 mm was used.

As the negative electrode, a lithium foil with a thickness of about 0.4M was used as a negative electrode with a diameter of 20.0mm.
The battery of the present invention (AI During battery assembly, polyethylene oxide in the positive electrode reacts with lithium perchlorate as an electrolyte to form a polymer electrolyte in the positive electrode.

FIG. 1 shows a longitudinal sectional view of the battery of the present invention, in which (1) is a positive electrode made of a mixture of a conductive polymer and a polymer electrolyte, and a positive electrode current collector (2) is connected to a standard can (3). ) is pressed against the inner bottom surface of the (4) is a lithium negative electrode, which is press-bonded to the inner bottom surface of the negative electrode can (6) via a negative electrode current collector (5). (7) is a separator, and (8) is an insulating hook.

For comparison, polyacetylene powder was used as the positive electrode,
Polytetrafluoroethylene as a binder: 90:
A comparative battery (DI) was prepared in the same manner as in Example 1 except that a molded body of the mixture mixed at a weight ratio of 10 was used.

[Example 2] As a positive electrode, polyacetylene powder topolyvinylpyrrolidone was mixed at a weight ratio of 90:10.

A battery (B) of the present invention was prepared in the same manner as in Example 1 except that this mixture was molded into a disk shape.

In this embodiment as well, during battery assembly, polyvinylpyrrolidone in the positive electrode reacts with lithium perchlorate as an electrolyte to form a polymer electrolyte in the positive electrode.

[Example 3] Prior to creating a positive electrode, first, polyethylene oxide and lithium borofluoride were dissolved in acetonitrile at a weight ratio of 3:1, and then acetonitrile fdE was emitted to dissolve the polyethylene oxide and lithium borofluoride. obtain a complex of Next, polyacetylene powder and the above composite were mixed in a ratio of 85:15.
After mixing thoroughly at a weight ratio of 20.0M in diameter and approximately 0.0M in thickness.
The 7th period molded into a disk shape is used as the positive electrode.

The negative electrode has a diameter of 20,0111. A lithium foil having a thickness of approximately α41Il11 was used, and the electrolyte was prepared by dissolving lithium borofluoride in propylene carbonate at a concentration of 1''/z.

Figures 2 to 4 show these batteries (AtCB) (01(D
), and Figure 2 shows the charging/discharging capacity efficiency.

Figures 3 and 4 show the charging and discharging characteristics at the 10th cycle.The cycle conditions were to charge at 2 mA for 1 hour, then discharge at 2 mA current, and bring the final discharge voltage to 1.5.
v.

From FIGS. 2 to 4, it can be seen that the battery of the present invention (AJ (BHO)) has improved charge/discharge capacity efficiency and improved cycle characteristics compared to the comparative battery (DI).

Note that in explaining the battery of the present invention, only the case where a conductive polymer electrode is used for one electrode is illustrated, but it is clear that conductive polymer electrodes can also be used for both the positive and negative electrodes.

(G) Effects of the invention As described above, in devices that use a conductive polymer electrode as at least one electrode, by using a mixture of a conductive polymer and a polymer electrolyte as the conductive polymer electrode, the charge/discharge capacity efficiency can be improved. It is possible to improve cycle characteristics and storage characteristics, and its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of a battery according to an embodiment of the present invention, and FIG.
Figures 4 through 4 are comparison diagrams of battery characteristics. FIG. 2 shows the charging/discharging capacity efficiency, and FIGS. 3 and 4 show the charging and discharging characteristics at 10 cycles g, respectively. (11-... Positive electrode, (21-- Positive electrode current collector, (
31-・Positive electrode can. (4)--Negative electrode, f51--Negative electrode current collector, (6)
...Negative electrode can. (71-... Separator, (8)... Insulating backing, (At(Bl(O), invention battery, (D
l... Comparison battery. Figure 2 Cycle time & (times) Figure 3 Figure 4 Time (hr)

Claims (1)

[Claims] (1) A nonaqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a nonaqueous electrolyte, wherein at least one electrode is made of a mixture of a conductive polymer and a polymer electrolyte.