JPS59173944A - Secondary battery - Google Patents

Abstract

PURPOSE:To prevent penetration of oxygen or moisture and oxidation of active material and increase battery life by constructing a battery case with resin films by which a metal film is covered or between which it is sandwiched. CONSTITUTION:In a secondary battery using organic high molecular compound having conjugated double bond such as polyacetylene as an electrode 1, a battery case 4 consists of 100mum thick resin films 6 between which a 20mum thick aluminum film is sandwiched and their end surfaces are reversely curled and heat- bonded in airtightness as shown in the figure. Polyethylene or polypropylene having good hot press bonding capability is preferable as the resin film 6, but polyester, polycarbonate, or nylon can be used by selecting a condition.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a secondary battery, and particularly to a secondary battery that consumes electrolyte during the charging process using an organic polymer compound having a conjugated double bond as at least one electrode. This is related to improvements in electrification.

[Prior art]

Organic polymer compounds having conjugated double bonds, such as acetylene polymers (polyacetylene), can be electrochemically (,
Anions such as to4-, PF5-, BF4-, or L12. It is known that it is possible to make p1p type and n type conductive polyacetylene by doping with cations such as ('C4H3)4N+. CJ, C,S, c:hem, Comm,
, (1979) pp594-595, C,&EN
, Su, 39 (1981): ]. It has been reported that if this electrochemical doping is used as a core, a rechargeable and dischargeable secondary battery can be made using polyacetylene. Using this membrane, propylev'j was used as an electrolyte and dopant.
) - perchlorate of tetrabutylammonium dissolved in honate C(C4Ht)4NCt04'l tJM IfC cell, open/l18 voltage 2.5 V, short circuit current 1
1.1 mA is obtained C J, C, S, che
m, comm.

(1981) I) I) 317-319).

Polyacetylene is obtained by polymerizing acetylene using a Ziegler-Natsuta catalyst. Films are formed by directly forming a film or by pressing gel or powder into a film. However, when manufacturing a secondary battery using a polyacetylene film as an electrode, there are the following problems.

(1) Since the voltage of the battery is high, the organic solvent used causes electrolysis during charging, and the impurities generated at that time affect the life of the battery.

(2) Since the voltage of the battery is high, water contained in the electrolyte solution electrolyzes, and the oxygen generated at that time deteriorates polyacetylene.

(3) The theoretical energy density of this battery is higher than that of conventional nickel-cadmium batteries or lead-acid batteries because the specific gravity of polyacetylene, which is the electrode active material, is low. The practical energy density achieved cannot be achieved using conventional technology. Therefore, in order to take advantage of the characteristics of a battery using a polyacetylene film, it is necessary to reduce the battery packaging factor.

(4) Polyacetylene is easily oxidized because it has conjugated double bonds. Therefore, it is necessary to use a battery case that can prevent oxygen and moisture from permeating.

(5) Since polyacetylene is used in the form of a film, it is desirable that the battery case also be in the form of a thin film.

Currently, various battery cases have been devised for negative batteries such as manganese batteries and lithium batteries, but these technologies alone cannot solve all of the above-mentioned problems.

[Purpose of the invention]

The present invention has been made in view of the above, and its purpose is to provide a secondary battery that can prevent harmful oxygen and moisture from entering and extend the life of the battery. be.

[Summary of the invention]

The present invention discloses that secondary batteries using organic polymer compounds with conjugated double bonds, such as polyacetylene, as electrodes have excellent initial current efficiency, but performance deteriorates with repeated charge/discharge cycles. This was done after confirming that impurities and moisture in organic solvents cause the oxidation rate of the electrode active material to increase and cause electrode deterioration if oxygen coexists with the battery when the battery is completed. In order to prevent this, the battery case is characterized by being constructed of a resin film covered with or sandwiched with a thin metal film.

[Embodiments of the invention]

Examples of the present invention shown in FIGS. 1 to 3 and 4
This will be explained in detail using figures.

FIG. 1 is a structural explanatory diagram showing an embodiment of the secondary battery of the present invention. In Figure 1, 2 and 1 are electrodes, and electrode 1
has a specific gravity of 0.91S and a thickness of 236pm.

A thin metal film having a thickness of 300 mm was attached to one side of a boria-cetylene film having a size of 4 cm by using a sputtering IJ apparatus. 2 is a supporting electrolyte solution, which is held in a separator made by pressing alumina wool to a thickness of 200 μm, and the supporting electrolyte solution is a supporting electrolyte and dopant (C*H5)4 NCtCh'k
60C, 10-"mm) (g) was dehydrated for over 24 hours, dehydrated with Tcan2, and then dissolved in twice-distilled acetonitrile solvent at a concentration of 1 mat/l. 3 is made of polytetrafluoroethylene. battery holder,
4 is a battery case.

By the way, in the present invention, as shown in FIG. 2, the battery case 4 is constructed by sandwiching an aluminum thin film 5 with a thickness of 20 μm between resin films 6 with a thickness of 100 μm, and the end faces are formed as shown in the figure. It was folded back and heat-pressed to create an airtight structure. The resin film 6 is made of polyethylene, which has good thermocompression bondability.

Polypropylene is preferred; depending on conditions, polyester,
Polycarbonate, nylon, etc. can also be used. In FIG. 2, polyethylene was used.

The above-mentioned secondary battery was charged at a current density of 5 mA/- for 1 hour, and then charged at 5 In A/- until the battery voltage reached 1■.
The battery was discharged at a current density of cA, and the current efficiency in each charge/discharge cycle, that is, the ratio (%) of the amount of discharged charge to the amount of charged charge, was measured, and the results are shown as a large curve in FIG.

In this case, charging and discharging were performed 29 times, and the current efficiency at the 29th time was 94%, and the battery voltage after the completion of the 29th charge was 2.8 ■. In addition, the practical energy density of the battery is 45 Whr/K at a doping rate of dopant (C2H5)4NC104 to polyacetylene of 6 m04%.
It was f.

For comparison, in FIG. 1, a secondary battery in which only the metal case 4 is made of a resin film without the aluminum thin film 5 and the other parts are the same as above was charged and discharged in the same manner as above, and each The current efficiency during charge/discharge cycles was measured, and the results are shown in eight curves in FIG. Although high current efficiency was shown in the 15th charge/discharge cycle, it gradually decreased in subsequent charge/discharge cycles, and at the 30th charge/discharge cycle, the current efficiency decreased to 30%. This is because the battery case 4 (made of an il-resin film) allows oxygen and moisture in the air to pass through and have an adverse effect.

In addition, the battery case 4 is made of SUS 304 with a thickness of 150μ.
An experiment was conducted on a secondary battery made of a thin plate with the other parts being the same as in the above example, and the practical energy density of this battery was 30 W at a doping rate of dopant (CzHs)4NC404 to polyacetylene of 5 m □ 7%) 1 r
It was as low as 7kg.

In contrast, the secondary battery according to the present invention has a battery case 4
The configuration shown in Figure 2 prevents the permeation of oxygen and moisture, improves current efficiency as described above, maintains it even with many charge/discharge cycles, and reduces practical energy consumption. Density is also improved.

FIG. 3 is a structural diagram showing another embodiment of a battery case for a secondary battery according to the present invention. In FIG. 3, a thin aluminum film 5 is laminated on the outside of a resin film 6.

Next, other embodiments of the secondary battery of the present invention will be described. In FIG. 1, the same polyacetylene film as in the above embodiment is used as the electrode 1, 100 mesh 5US304 gold steel is used as the current collector for sputtering a metal thin film, and the separator holds the supporting electrolyte solution 2. A secondary battery made of polypropylene and a battery case 4 having the configuration shown in FIG. 3 was charged and discharged in the same manner as in the above example, and the current efficiency in each charge and discharge cycle was measured. The results are shown in FIG. 4 by curve C. In the case of this example, the current efficiency was 81% at the 29th charge/discharge cycle, which is somewhat lower than in the case of the large curve, but as in the case of the large curve, the current efficiency decreases depending on the number of charge/discharge cycles. There isn't. Further, the battery voltage after the 29th charge was 3.1V.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to prevent the intrusion of harmful oxygen and moisture, extend the life of the battery, and improve the practical energy density by reducing the weight. There is an effect.

[Brief explanation of drawings]

Fig. 1 is a structural diagram showing one embodiment of the secondary battery of the present invention, Fig. 2 is a structural diagram showing one embodiment of the battery case of Fig. 1, and Fig. 3 is another embodiment of the battery case. Structure diagram showing 4th
The figure is a relationship diagram between charge/discharge cycles and current efficiency for detailed explanation of the present invention. DESCRIPTION OF SYMBOLS 1... Electrode, 2... Supporting electrolyte solution, 4... Battery case, Death... Aluminum thin film, 6... Resin film. N No Figure Vt21 蓓 4 Figure Jōdensu Ikutsu b number (Continuation of page 1) Applicant Showa Denko Co., Ltd. 1-13-5 Shiba Daimon, Minato-ku, Tokyo

Claims (1)

[Claims] 1. In a secondary battery in which at least one electrode is composed of an organic polymer compound having a conjugated double bond and which consumes electrolyte during the charging process, the battery case covers or sandwiches a metal thin film. A secondary battery characterized in that it is made of a resin film containing a resin film. 2. The secondary battery according to claim 1, wherein the metal thin film is an aluminum thin film. 13,
3. The secondary battery according to claim 1, wherein said resin film is made of polyethylene, polypropylene, polyester, polycarbonate, or nylon. 4. The secondary battery according to claim 1, 2, or 3, wherein the battery case has an airtight structure by pressure-bonding the resin film on the end face.
j5, the secondary battery according to item 4, wherein the organic polymer compound is polyacetylene;