JPS62117279A - Photo-secondary cell - Google Patents

Abstract

PURPOSE:To improve the charging efficiency by employing such positive electrode material as mainly composed of CuxZrS2 (0<x<0.15). CONSTITUTION:A negative electrode mainly composed of metal copper, Cu<+> ion conductive solid state electrolyte and a positive electrode mainly composed of sulfide to be shown by CuxZrS2 (0<x<0.15) are laminated sequentially to enable charging by radiating light onto the positive electrode. ZrS2 has Cu<+> ion conductivity as low as 4X10<-9>S/cm which may be one cause for lowering the photo charging efficiency. But when Cu is thermally intercalated previously, the ion conductivity will increase, resulting in improvement of photo charging efficiency.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a secondary battery that can be charged with light rather than electricity, that is, a battery that functions as a combination of a solar cell and a secondary battery.

Conventional technology Many attempts have been made to develop secondary batteries that can be charged using light, as shown in the review article by Kaneko, Electronics, pp. 97-104 (59-10), but the only ones that have been put into practical use are solar batteries. It uses a battery to charge a normal secondary battery. In addition to the two-stage type, which stores power generated by solar cells in a secondary battery, electrodes made of a semiconductor such as n-type TiO2 can be replaced with a metal such as platinum, or p-type G.
a The semiconductor electrode is immersed in an electrolytic solution together with an electrode made of a semiconductor such as P, and the semiconductor electrode is irradiated with light to cause charge separation.
There have also been attempts to oxidize and reduce substances in the electrolyte with photo-induced charges (generating holes in the conductive band and electrons in the conductive band) and storing this as an active material, which is then used during discharge, but this has not yet been put to practical use. The area has not been reached.

In order for the photo-excited charge to carry out the subsequent oxidation/reduction reaction, the oxidation/reduction potential of the substance in the electrolyte must be above the top of the conductive band of the semiconductor electrode, and the reduction potential be below the bottom of the conductive band. ■ In order to perform as much charge separation as possible through photoexcitation, it is necessary that the band gap of the semiconductor electrode be small, but if the band gap is too small, the condition (■) cannot be satisfied and the subsequent electrochemical reaction will not proceed. . Therefore, in order to satisfy the conditions (1) and (2), absorb sunlight or fluorescent lamp light, and efficiently proceed with the reaction, the band gap of the semiconductor is preferably 1 to 2. A semiconductor with a band gap of about eieV,
(n-type St -1, 1eV, n-type GaAs-1, 35e
Both Tio2.
Currently, materials such as ZnO are limited to materials with a band gap of 3.0 to 3.2 QV.

Further, recently, much research has been conducted on secondary batteries using dichalcogenides of transition metals of the ■, v, and ■ groups as positive electrode materials. Most of them use Li as the negative electrode material and an organic electrolyte.

Very recently, dichalcogenides of these transition metals have been shown to be able to transfer ions in and out not only by electric current but also by light. John Compound on Layer Combination", Straftia and Bonding (H, Tr 1butch," Photoelec
trochemnergy conversion
involving transition
etald-+;tates and 1nter
Calation compound of Lay
er compounds”, 5structures
and Bonding49.162~168'8
2) summarizes the research of his own and others and discusses the possibility of batteries that can be charged with light. Considering the use of sunlight, batteries with -Li as the negative electrode require too much energy to charge, making it impossible to charge them with high efficiency. From the standpoint of efficiency, it is predicted that it would be better to replace the negative electrode with something like Cu, which has a more aggressive oxidation/reduction potential. This is mentioned in ■ above.

This can be easily considered from the condition (2). ! It is necessary for the electrode to maintain semiconductivity during the process of photocharging, and B.G. Jacob et al. Journal on Physics (Solid State Physics) B deals with the intercalation of Fe or Cu into ZrS or Hf52.

G., Jacob, et al., 1, Phys.
C, (Solid 5tatePhys) 12, 21
89 ('79), we state that these disulfides are promising as photoelectrodes.Problems to be solved by the inventionThe inventors previously developed n-type ZrS and Hf52. We proposed a secondary battery that can be charged using the light used. However, batteries using the above-mentioned materials as positive electrodes have the drawback of low charging efficiency as a battery during photocharging.

Means for solving the problems Cu xZ r 52 (0<x
<0.15) is used.

The action Z r S 2 is Cu + (on conductivity is 4 x 1 o
-9S/C! It is small at 1 t, which is one of the causes of lowering the charging efficiency during optical charging. However, if Cu is thermally intercalated in advance, the ionic conductivity increases significantly, thereby improving the charging efficiency of photocharging.

Example Next, embodiments of the present invention will be described.

<Example 1> The materials constituting the battery are as follows.

Positive electrode: Cu,..., ZrS2 powder + RbCu4 1.5" 3.5 powder (weight ratio 2:3)
・・・・・・・・・・・・・・・・・・13 Q In
q Solid electrolyte: RbCu411.5Ct3.5 powder -
-50,'lq Negative electrode: Cu powder + Cu 1.59
S powder + RbCu411.5Ct3,5 powder (weight ratio 4
:19:5)・・・・・・・・・ ・ ・・
5 Q m da The above positive electrode powder, solid electrolyte and negative electrode powder were pressed into three layers under a pressure of about 3 tons, and the diameter was 10.
ffiff battery pellets were constructed as shown in FIG.

1 is a positive electrode layer, 2 is a solid electrolyte layer, 3 is a negative electrode layer, and -4
A transparent electrode was used in which N203 doped with SnO2 was deposited on glass. 5 is a current collector made of styrene-butadiene rubber with a wire diameter cuff ~8μ771.
A conductive rubber in which carbon fibers having a length of 30 to 100 μnL were dispersed was used. 6 is a lead wire, and R is a package using highly insulating resin. The above battery is 200μA
Fig. 1 shows the change in closed circuit voltage over time when light irradiation was performed, with the time axis set at the origin of the time axis when the electromotive voltage decreased to 0.1 volt. The circle mark indicates this example, and the mark indicates a comparative example in which ZrS2 is the main material of the positive electrode. A 100 W Xs lamp was used as a light source, and irradiation was performed at a distance of 501 cm. As you can see from Figure 1, Z r
Compared to S2, the present example in which Cu o: 1Z r S 2 was used as the main material of the positive electrode had a faster voltage recovery after irradiation with light, which means that the charging efficiency was higher. The relationship between the molar amount of Cu in Z r S 2 and ionic conductivity is shown in the following table. An increase in ionic conductivity improves the charging efficiency of photocharging.

Table <Example 2> Cuo as the positive electrode. 5ZrS2+RbCu4I, 5
A mixture of C4,5 at a weight ratio of 2:3 is 6 Q Mq
The battery was manufactured under exactly the same conditions as in Example 1 above, and the first battery was discharged under a soKΩ constant resistance load.
FIG. 3 shows the change in closed circuit voltage over time when the same light irradiation as shown in the figure was performed.

Note that the positive and negative electrode materials include not only powder but also sputtered films, C
It may also be a VD film or the like. The reason for using a solid electrolyte is that when the electrolyte is a liquid, when light is irradiated at the joint surface with the positive electrode, both cations and anions participate in the reaction, which causes corrosion of the positive electrode material. In the case of the solid electrolyte used in the original secondary battery, only Cu+ reacts, and the positive electrode material does not corrode. Note that Cu xZ r S 2 of the above positive electrode material is a non-stoichiometric compound of Zr and S, and this is Cu, Zr5y (1,8:SY≦2.
It goes without saying that the same result can be obtained with 1).

Effects of the Invention The increase in voltage after light irradiation is much larger than that in a case where ZrS2 is the main material of the positive electrode. This means that the charging efficiency of optical charging is much greater.

In other words, by intercalating Cu into Z r S 2 in advance, the ionic conductivity is increased and the charging efficiency is also improved.

[Brief explanation of drawings]

FIG. 1 is a characteristic diagram of a photo secondary battery according to an embodiment of the present invention, and FIG.
The figure is a block diagram of a secondary battery of the same type, and FIG. 3 is a characteristic diagram of a secondary photovoltaic battery according to a different embodiment of the present invention. 1...Positive electrode, 2...Solid electrolyte, 3...
... Negative electrode, 4... Transparent electrode, 5... Current collector, 6... Lead wire, 7... Sealed package. Name of agent: Patent attorney Toshio Nakao and 1 other person
1 Figure Time (Division 2 Figure 3 Light Figure 3 θ This 4 6 δ
10 questions

Claims (1)

[Claims] A negative electrode mainly composed of metallic copper, a Cu^+ ion conductive solid electrolyte, and a positive electrode mainly composed of a sulfide represented by Cu_xZrS_2 (0<x<0.15) are laminated in sequence, and the positive electrode is irradiated with light. A photo secondary battery characterized by being rechargeable by: