JPS6017871A - Chargable battery - Google Patents

Abstract

PURPOSE:To provide a lithium battery having a high electric capacity and a long cycle life by using as the positive electrode, a sheet containing active carbon packed in a high density. CONSTITUTION:A positive material 6 consists of mixture consisting of active carbon powder and fluorine resin fiber. A metallic net, lath plate or punching metal is used as a positive current collector 5. Lithium metal is used as a negative electrode 3. Electrolyte is prepared by dissolving lithium perchlorate, lithium borofluoride or their mixture in propylene carbonate, gamma-butyrolactone, DME or mixture consisting of two or more of these solvents. The battery according to this invention, since having a great battery capacity and a long charge-and-discharge cycle life, can be favorably used as a mobile d.c. power source, a back-up power source or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a rechargeable battery used in a mobile DC power source, a backup power source, and the like.

Structures of conventional examples and their problems Conventionally, high energy density batteries using lithium as the active material for the negative electrode, so-called lithium batteries, have used a mixture of fluorocarbon and carbon black, or manganese dioxide and carbon black, or manganese dioxide and carbon black for the positive electrode. Using a mixture with a binder, lithium metal is used as the negative electrode, propylene carbonate or γ-butyrolactone in which lithium perchlorate or lithium borofluoride is dissolved in the electrolyte, or these and 1.2 dimethoxyethane (hereinafter referred to as DME) are used. ) is used. However, in the case of this system, it is used as a primary battery, and charging is not possible at this stage.

On the other hand, rechargeable DC power batteries include batteries that use activated carbon fiber as the positive and negative electrodes and propylene carbonate in which ammonium perchlorate is dissolved as an electrolyte, or batteries that use activated carbon fiber as the positive electrode. , a device using lithium metal as the negative electrode and a mixed solution of propylene carbonate in which lithium perchlorate is dissolved as the electrolyte and DME has been announced.

Although these batteries are mainly charged with electric charges in the electric double layer, they do not necessarily have sufficient electrical capacity or charge/discharge cycle life as batteries, and their internal resistance is also high due to their high electrical resistance.

Furthermore, it is difficult to lower the internal resistance of these devices due to the method of attaching the activated carbon fiber to the positive electrode or the high electrical resistance of the positive electrode, and the charging and discharging efficiency is also poor, so there is still much room for improvement. there were.

OBJECTS OF THE INVENTION The object of the present invention is to provide a rechargeable battery using lithium metal as a negative electrode, which has a large electric capacity and also has a long charge/discharge cycle life.

Structure of the Invention In order to achieve the above objects, the present invention uses a mixture of activated carbon powder and fluororesin fiber as a positive electrode material, and uses a metal net, a lath plate, or a punched metal as a current collector.
Lithium metal is used as the negative electrode, an electrolyte is used, a monomer liquid or a mixture of propylene carbonate, γ-butyrolactone, and DME is used as a solvent, and lithium perchlorate or lithium borofluoride alone or in a mixture is dissolved as a solute. It uses the same thing.

Conventionally, systems similar to this system include the activated carbon fiber/Li CLO4 + propylene carbonate) and DME/Li systems, as described above, but in this case, a sheet-like thin activated carbon fiber cloth was used as the positive electrode. ing. However, although this has a large surface area, its binding strength is low;
It has the disadvantage that it is difficult to increase the density, and as a result, the electric capacity is small and the charge/discharge cycle life is limited.

However, in the present invention, as the positive electrode, activated carbon powder is kneaded with 7 resin fibers and uniformly mixed and dispersed, so the strength is much l- larger than that of activated carbon fiber alone. The surface area of activated carbon powder determined by the BET method is
Approximately 2000 m''/P't can be selected arbitrarily.Furthermore, when fluororesin fibers are mixed, even if the packing density of activated carbon is considerably increased by applying pressure, etc.
Activated carbon powder will not fall off. In this respect,
In the case of activated carbon fibers, even if they are kneaded with fluororesin fibers, it is difficult to obtain a homogeneous mixture and it is also difficult to form them into a sheet form.For this reason, the present invention is not found in conventional activated carbon fiber cloths. High electrical capacity due to the use of a high-density packed activated carbon sheet with excellent strength as the positive electrode.

This allows for a long cycle life.

The metal used as the current collector of the positive electrode must be selected from a metal that has excellent corrosion resistance against organic electrolytes, and stainless steel containing no nickel and 20% by weight or more of chromium or titanium is suitable.

Furthermore, as for activated carbon, the finer the powder and the larger the surface area, the larger the electric capacity.

On the other hand, rather than using fiber-like fluororesin from the beginning, the fluororesin fiber is made by kneading an aqueous dispersion in which fine powder of a hexafluorocarbon resin is dispersed in water and activated carbon.
If the 7-no-resin is made into fibers and dispersed during the kneading process, it is possible to mix it more densely and uniformly.

Description of examples The present invention will be explained below with reference to Examples.

(Example 1) Surface area is 800.1000, 1200, 1400°16
Prepare 80 parts by weight of each activated carbon powder of 0077Z2/'l, knead this with 20 parts by weight of an aqueous dispersion of fluororesin (solid content: approximately 6o%), and form a sheet using two rolls. After molding, it was transferred to a titanium lath plate with a thickness of 0.2 cylinders. After drying at 160° C. for 2 hours, the pellets were adjusted to a thickness of 0.6 and punched into pellets with a diameter of 14. The weight of each pellet at this time is 1o
The pellet thus obtained was used as a positive electrode, a lithium metal with a thickness of 0.5 rran and a size of 12M was used as a negative electrode, and a polypropylene nonwoven fabric was used as a separator.

7 L - As an electrolyte, propyl noncarbonate and DME were mixed at a volume ratio of 1:1, and lithium perchlorate was added to this mixed solution at a concentration of 1 mol/l.

Using these monthly interest rates, I made a lithium battery as shown in the figure. Its size is 20 mm in diameter and 1.6 mm thick.

First, an insulating sealing ring 1 made of polypropylene is combined with a stainless steel sealing plate 2 that also serves as a negative terminal.
Place the opening on top. Then, a negative electrode 3 made of lithium metal is placed in the sealing plate 2, followed by a dish-shaped separator 4, and the electrolytic solution described above is poured into the sealing plate 2. After that, a pellet-like positive electrode 6 having a current collector 6 is placed on the separator 4,
A positive electrode case 7 made of stainless steel containing 20 parts by weight of chromium and no nickel is coupled to the outside of the sealing ring 1, and the opening of the case is caulked inward to seal it.

The batteries thus obtained are designated A1 to A6 in order of decreasing surface area of the activated carbon.

(Example 2) Activated carbon 8o heavy front with a surface area of 1400 m"/P,
20 parts by weight of the solid content of the aqueous diversion of the fluororesin were thoroughly kneaded, and a pellet positive electrode body was produced in the same manner as in Example 1.

The following four types of electrolytes were prepared.

(1) 1 mol/l of LiBF4 in γ-butyrolactone
added to the concentration of

(2) γ-butyrolactone and DME in a volume ratio of 1:
1 and to which LiB F 4 was added at a concentration of 1 mol/l.

(3) LiCL○4 is added to propylene carbonate at a concentration of 1 mol/la degree.

(4) Propylene carbonate and DME are mixed at a volume ratio of 1:1, and L i Ct O4 is added to this mixture at 1 mol/l.
Added to a concentration of l.

Example 1 was carried out using each of these electrolytes and the above-mentioned positive electrode body.
I made a battery using the same method. These batteries are B1-B
Set it to 4.

(Example 3) 91゛- As the current collector of the positive electrode, a lath, a net, and a punched metal made of stainless steel containing 20 parts by weight of chromium and no nickel as an alloy component were used, and the surface area of the activated carbon powder was Also 1400rr? /P, and a battery was produced under all other conditions as in Example 1. These batteries are designated as 01 to C3.

As a comparative example, a battery was constructed under the same conditions as in Example 1 except that an activated carbon fiber cloth was used for the positive electrode. Let this be D.

Note that the weight of the activated carbon fiber cloth at this time was 40 Tng.

Types of these A-D and 1-6'! Using batteries numbered f, the internal resistance (Ifl) and discharge conditions of each battery are as follows:
After 200 cycles, one cycle was 1 mA for 10 hours at a constant voltage of 3.6 V and 20 hours, constant current discharge was performed at 1 mA, and the discharge time to a final voltage of 2 OV was measured. The results are shown in the table below.

The following margin ol- "As is clear from the previous person, in Example 1, the larger the surface area of the activated carbon, the longer the discharge time, especially when the surface area is 120.
The discharge time of 0 m'/y or more is 20 hours or more, which is excellent.

Moreover, in Example 2, the difference depending on the electrolyte was small, and B-1 to B
In terms of -4, it can be said that the B-4 electrolyte is better.

Furthermore, when comparing the morphology of the positive electrode current collector in Example 3, there was no difference in any case.

11 - According to the inventors' tests d and j, the current collector of the positive electrode can be arbitrarily provided not only in the center of the positive electrode layer but also in the upper part of the layer or the lower part of the layer. No difference was observed depending on placement.

Compared to these A-C batteries, the discharge time of the comparative example is 1
The test time was only 6 hours, and the internal resistance was 26Ω, which was considerably higher than 8-C, clearly demonstrating the superiority of the present invention.

In the above embodiments, a flat coin-type battery was used, but similar effects can be expected with button-type or cylindrical batteries.

Effects of the Invention As described above, the rechargeable battery of the present invention can withstand a longer charge/discharge cycle life than conventional batteries, has a large electric capacity, and has an extremely wide range of applications.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of a coin-type lithium battery in an embodiment of the present invention. 1...Insulating side rolling, 2...Sealing plate, 3...Negative electrode made of lithium metal, 4...
...Separator, 6...Positive electrode current collector, 6...
...Positive electrode, 7...Positive electrode case 0

Claims (1)

[Scope of Claims] (1) A positive electrode made of a mixture of activated carbon powder and fluorine patterned fat fibers and a metal current collector, and a negative electrode made of lithium metal;
A rechargeable battery characterized by using an electrolyte containing an organic solvent. (2) The surface area of activated carbon powder is 1200 to 20 by BET method.
The rechargeable battery according to claim 1, which is oOm2/y. A rechargeable battery according to claim 1. (4)! The solution uses a half-volume solution or a mixture of propylene carbonate, γ-butyrolactone, or 1,2-dimethoxyethane as a solvent, and uses lithium perchlorate or lithium borofluoride alone or as a mixture as a solute. A rechargeable battery according to any one of claims 1 to 3.