JPS62117278A - Photo-secondary cell - Google Patents

Abstract

PURPOSE:To obtain a larger discharge current by employing a material mainly composed of a compound of ZrS2 and Pb black powder as a positive electrode material. CONSTITUTION:The photo-secondary cell in the caption comprises a negative electrode mainly composed of metal copper, a Cu<+> ion conductive solid state electrolyte and a positive electrode mainly composed of a compound of ZrS2 and Pb black powder and can be charged by radiating the light onto the positive electrode. Main cause of polarization is the activating energy for moving the charge on a contact face between the electrolyte and the positive electrode material. The lower the activating energy, the quicker the electrons are passed and received thus reducing the polarization. When Pb black powder is mixed into ZrS2, the above activating energy will lower resulting in reduced polarization.

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 with light, as shown in the review of Kaneko Tsuyoshi, Electronics, P9 Ryo~104 (S59/10), but only a few have been put into practical use. It uses solar cells to charge regular secondary batteries. In addition to the two-stage type that stores power generated by solar cells in a secondary battery, there are also electrodes made of a semiconductor such as n-type T102 made of a metal such as platinum or a semiconductor such as p-type GaP. The semiconductor electrode is immersed in an electrolytic solution together with the electrode, and the semiconductor electrode is irradiated with light to cause charge separation (t, (
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 and reduction reactions, the oxidation and reduction potentials of the substances in the electrolyte must be above the two ends of the conductive band of the semiconductor electrode, and the reduction potential must be below the bottom end of the conductive band. ), it is necessary for the band gap of the semiconductor electrode to be small in order to perform as much charge separation as possible by photoexcitation, but if the band gap is too small, the condition in ■ will not be satisfied and the subsequent electrochemical reaction will be delayed. is not progressing. Therefore, the band gap of a semiconductor that satisfies the conditions (1) and (2), absorbs sunlight or fluorescent lamp light, and is desirable for the reaction to proceed efficiently is 1 to 2.5 e.
However, semiconductors with such a band gap, such as n-type Si 1.1 eV, n-type GaAs
~1.36 eV and CdS ~2.4 eV both have the problem of being involved in reactions and corroding, and those that are stable in aqueous electrolytes can only be used with ultraviolet light. Currently, the band gap is limited to materials with a band gap of 3.0 to 3.2 eV, such as T i02 and Z n○, which cannot be used.

Further, recently, much research has been conducted on secondary batteries using dichalcogenite, a transition metal of the IV, V, and Vl groups, as a positive electrode material. Most of them use Li as the negative electrode material and an organic electrolyte.

Very recently, it has been reported that these transition metal dichalcogenides can transport ions in and out not only by electric current but also by light. For example, H. Tripich, Pafoto Electrochem Energy Conversion Involving Transition Metal D Stein and Intercalation Compound Op Layer Combunds, Straftia & Bonde, Inc. (H, Tributc)
h,” Photoelectrochem ener
gyconversion involving
ttansion metal-states
and1ntercalation com
“pound oflayar compounds”
, 5structure and Bonding49.
162-1es's2) synthesizes his own and others' research and outlines 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. The -F efficiency predicts that it would be better to replace the negative electrode with something like Cu, which has a more negative oxidation selectivity potential. This is mentioned above ■,■
This is easily conceivable from the following conditions. In addition, it is necessary for the electrode to maintain semiconductivity during the process of photocharging, and the intercalation of Fe or Cu into ZrS2 or Hf52 was discussed in the journal Physics Sea by B.G. Jacob et al.
Physics (B, G, Jacob, et a
lT.

Phys, C, (Solid 5tate Phys
) 12, 2189 (°了9)) and states that these disulfides are promising as photoelectrodes.

Problems to be Solved by the Invention The inventors previously proposed a light-chargeable secondary battery using n-type Z r S 2 and Hf52. However, batteries using the above-mentioned materials as positive electrodes have the drawback of large polarization during discharge.

However, as a solution to one point, a material mainly consisting of a mixture of Z r S 2 and Pd black powder is used as the positive electrode material of the battery.

A major cause of battery polarization is the activation energy of charge transfer at the interface between the electrolyte and cathode material. As it passes through the electrolyte, Cu+ receives electrons from the positive electrode material, becomes Cu, and is stored in the positive electrode material.This flow of electrons functions as a battery. The energy consumed when transferring electrons to and from a substance is called the activation energy of charge transfer.

Of course, the lower the activation energy, the more quickly electrons can be exchanged, and the polarization of the battery will be smaller. Z
r S 2 K P d When the black powder is mixed, the activation energy mentioned above is lowered, and as a result, the polarization is reduced. Example (Example 1) The materials constituting the battery are as follows. be.

Positive electrode: Z r S 2 powder + Pd powder + RbC
u 4 engineering+, sC#3.5 powder (MftJ=Hi2:0
．． 02:3) ・=,,,,60mq
Solid electrolyte; Rb Cu 4I4. scl3. s
Powder ・-=-50mq negative i: Cu powder +
Cu1.5aS powder 10RbCu4, 5" 3.5mm (weight ratio 4:19:5)...50m
The above positive electrode powder, solid electrolyte, and negative electrode powder were pressed into three layers under a pressure of about 3 tons to form a battery pellet with a diameter of 1 omm, as shown in FIG. 3. 1 is the above-mentioned positive electrode layer, 2 solid electrolyte layers, 3 (・→ negative electrode layer), and 4 is a transparent electrode in which In 203 doped with SnO2 is vapor-deposited on a glass plate. 517i (i%
Electrically suspended styrene-butadiene comb with wire diameter of 7 to 8I1
One is a lead wire made of conductive rubber in which carbon fibers are dispersed and has a length of 30 to 100 μm, and 7 is a package made of highly insulating resin.

While discharging the above battery at 200/JA, light irradiation
FIG. 1 shows the change in closed circuit voltage over time when the n-off cycle is repeated. 100W for light source
Irradiation was performed using an Xs lamp at a distance of 5oCM. The discharge characteristics of this battery are shown in FIG. The discharge current is 200
In μA, as in Fig. 1, the ○ mark indicates this example, and the mark indicates Z r
S2 is used as the main material of the positive electrode as a comparative example, and it can be seen that the discharge characteristics of this example were significantly improved.

<Example 2> ZrS +Pd+RbCu4I, -504 as positive electrode
3. .

were mixed at a weight ratio of 2:0.04:3.
This graph shows the time change in the Samurai closed-circuit voltage when light irradiation was turned on and off while discharging a battery using 09 and using the same conditions as in Example 1 above with a constant resistance load of 50Ω. is shown in Figure 4.

In addition, Z r S 2 of the above positive polar moon 1 is a non-stoichiometric compound, and this is Zr5y (Y≦2.1 to '-8).
), but the reason for using a solid electrolyte is that when the electrolyte is a liquid, when light is irradiated at the junction surface on the positive electrode, both cations and anions participate in the reaction. However, in the case of solid electrolytes used in water-based secondary batteries, only Cu+ reacts, and corrosion of the positive electrode material does not occur.

Effects of the Invention As described above, the present invention uses a material made of a living body of a mixture of Z r S 2 and Pd black powder for the positive electrode, thereby drastically reducing the overall polarization during battery discharge. I was able to obtain a discharge current.

[Brief explanation of drawings]

1 and 2 are characteristic diagrams of a photovoltaic cell according to an embodiment of the present invention, FIG. 3 is a configuration diagram of the same cell, and FIG. 4 is a characteristic diagram of a photovoltaic cell 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 No. 1
Figure Tokukai (Tokkai) Figure 2 Denginnya (Hemorrhoid Review) Figure 3 Light Officer Kei ↑ Bakkeshi

Claims (1)

[Claims] It is composed of a negative electrode mainly made of metallic copper, a Cu^+ ion conductive solid electrolyte, and a positive electrode mainly made of a mixture of ZrS_2 and Pd black powder, and can be charged by irradiating the positive electrode with light. A photo secondary battery characterized by: