JPS634557A - Photo-secondary battery - Google Patents

Abstract

PURPOSE:To prevent decomposition caused by light irradiation by using MoX2 (X is S, Se, or Te) as a main material of a positive electrode. CONSTITUTION:A battery consists of a negative electrode mainly comprising copper, a Cu<+> ion conductive solid electrolyte, and a positive electrode mainly comprising n type MoX2 (X is S, Se, or Te). By irradieting light to the positive electrode, the battery is charged. In the band structure of MS2 (M is Ti, Zr, or Hf) and MoX2 (X is S, Se, or Te), when light is irradiated to MS2, a hole is produced in P orbit of S. The P orbit of S is a valence band of MS2, or a chemical bonding part of MS2. When the hole is produced there, the chemical bond of MS2 is cut at high atmospheric temperature, resulting in the decomposition of MS2. On the other hand, when light is irradiated to MoX2, a hole is produced in t2g orbit which is produced by the interaction of Mo and X. Therefore, even if the hole is produced there, the chemical bond of MoX2 is not cut.

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a secondary battery that can be charged with electricity or light, a solar cell, and a secondary electrode. The invention relates to an all-solid-state photovoltaic battery that functions in combination.

Conventional technology Many attempts have been made to develop secondary batteries that can be charged with light, as shown in the review of Masao Kaneko's Electronics, pages 97-104 (October 1982), but only one has been put into practical use. It uses a solar cell to charge a normal secondary battery.

In addition to the two-stage type that stores electricity generated by solar cells in a secondary battery, there are electrodes made entirely of semiconductors such as n-type TlO2, metals such as platinum, or semiconductors such as p-type GaP. The semiconductor electrode is immersed in an electrolytic solution along with the electrode, and the semiconductor electrode is irradiated with light to cause charge separation (generating holes in the valence band and electrons in the conductive band), and the photo-induced charge oxidizes and reduces substances in the electrolytic solution. Attempts have also been made to store this as an active material and use the entire container during discharge, but this has not yet reached the level of practical use. In order to cause the subsequent oxidation/reduction reaction to occur with photo-excited charges, the oxidation/reduction potential of the substance in the electrolyte must be above the upper end of the valence band of the semiconductor electrode, and the reduction potential be below the lower end of the conductive band. In order to achieve as much charge separation as possible through zero-element excitation, it is necessary that the bandgap of the semiconductor electrode be small; however, if the bandgap is too small, the condition (2) cannot be satisfied and the subsequent The electrochemical reaction that occurs does not proceed efficiently. Therefore, ■
The bandgap of a semiconductor that satisfies the conditions of , for example n-type 3i (~1
．． 1+5V), n-type 04MUS (~1,35ev),
CdS (~2.4 eV) has the problem that it itself participates in reactions and corrodes, and the only one that is stable in an aqueous solution is TiO2, which can only be used with ultraviolet light.
, ZnO, and other materials with a band gap of 3.0 to 3.2 eV are currently used.

Recently, much research has been carried out on secondary batteries using dichalcogenite, a transition metal of the IV, V, and Vl groups, as a positive electrode material. Many of them are negative materials for Li fjl,
It uses an organic electrolyte.

Very recently, it has been reported that dichalcogenites of these transition metals can transport ions in and out not only by electric power but also by light. For example, H Tripich, Photoelectrochemical Energy Conversion Involving Transition Metal De-Stiso and Intercalation Oplayer Combine, Straftia and Bonding (H, Tributch = photo
electrochemical energy con
version involving Tr2Lnsit
ion metal d-5tate andint
ercalation of 1ayer compo
unds,”5structure and Bond
ing 49, 162-166'82) summarized the research of his own and others and described the possibility of a battery that can be charged with light. Considering the use of sunlight, batteries with Lii negative electrodes 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 can be easily considered from the conditions (1) and (2) above. In addition, in the process of photocharging, it is necessary for the electric current to maintain its semiconducting properties, and therefore
P.G. Jacobike Journal Physics Sea (Solid) dealing with intercalation to 52
State Physics (B, G, Jacob
, et al J, Phys, C3 (Solid
5tate Phys) 12,2189. 'Ryo9
)) states that these disulfides are promising as photoelectrodes.

However, the above review merely states expectations and does not completely solve the practical problems of this type of battery. In other words, it is not possible to create a battery that is sufficient for practical use using only the materials described in the review article, as will be described later. Moreover, Cu
There is no mention of the all-solid-state photosecondary battery of the present invention using an ion-conductive solid electrolyte, and no suggestion is given about solving the problems described below in order to put this into practical use.

Problems to be Solved by the Invention The present invention is different from what Tributch expected in that charging is performed by utilizing deintercalation of Cu ions by light from an electrode using n-type transition metal dichalcogenite. does not change. By the way, when a solution electrolyte is used in these n-type semiconductor electrodes, it is known that cations are deintercalated or anions are intercalated by the action of light. Whether these reactions proceed or not depends on the energy level of Al intercalation, the Fermi level, and the oxidation/reduction potential of each ion within the forbidden band on the semiconductor electrode side.
is determined by whether or not they are in relative positions as shown in FIG. In other words, in order to enable charging by deintercalation of cations, (A/A) must be EX and the oxidation/reduction potential of cations! , and when the anion is oxidized or reduced, only the CU ion can move, so the anion intercalation reaction does not proceed. Therefore, the oxidation of cations
Paying attention only to the relative positions of the reduction potentials, it is sufficient if this satisfies the conditions shown in FIG. Therefore, there is an advantage that there are fewer restrictions on material selection. However, on the other hand, MB2 (Ml''iT, Zr) is used as the main material of the positive electrode.

Hf) had the disadvantage that MB2 decomposed when irradiated with light at a high temperature of 60° C. or higher.

Means for Solving the Problems According to the present invention, the main material of the positive electrode is MoX2 (where X is any one of S, Ss, and Te) all around the cathode.

The band structures of MB2 (M is Ti, Zr, If) and MoX2 (X is S, Ss, Te) are shown in Figures 5(a) and 5(b), respectively.
Shown below. Figure 5<'a->-xAs you can see, MB
When 2 is irradiated with light, a hole is generated in the P orbit of S.

The P orbital of S is the valence band of MB2, that is, the part that forms the chemical bond of MB2, and when a hole is created there,
When the ambient temperature is high, the chemical bonds of MB2 are broken, resulting in decomposition of MB2. However, as can be seen from Figure 5(b), when MoX2K light is irradiated, holes are generated in the t2g orbit caused by the interaction between Mo and X, so holes are generated here. Mo Mo
The chemical bond of X2 never breaks.

As mentioned above, the main material of the positive electrode is MoX2 (X is S
, Se, or Te), decomposition due to light irradiation will not occur.

Example Hereinafter, the present invention will be explained in detail with reference to Examples.

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

Positive electrode: MoSe2 powder + RbCuaIt5C:Ha5 powder (weight ratio 2:3) 6
0■ Solid electrolyte: RbC; u411.5+dJ15 powder ・=・soq negative electrode: Cu powder + Cu, 59S powder-l-RbCu4ItsCJ, xs powder (weight ratio 4:1
9:5)...50 ■ The above positive electrode powder, solid electrolyte, and negative electrode powder were made into a layered battery pellet, which was constructed as shown in FIG. In the figure, 1 is the above-mentioned positive electrode layer, 2 is the solid electrolyte layer, and 3 is the negative electrode layer. No. 4 was a transparent electrode in which In2O3 doped with 5n02f was deposited on a glass substrate all around the circumference. 5 is a current collector on the negative electrode side made of styrene-butadiene rubber with a diameter of 7 to 8 μm and a length of 30 to 100 μm.
A conductive rubber having m carbon fibers dispersed therein was used. 6 is a lead wire, and 7 is a package using a highly insulating resin. 8
is a diode to prevent reverse current during photocharging.

FIG. 2 shows the change in battery voltage over time when the above battery was repeatedly discharged and photocharged. -The ambient temperature is 60°C, the discharge is 100 μA for 1 hour, and the light source except for photo-charging is a 10oW Xe lamp.The distance to the light source is n & total 5oc! Light was irradiated for 1 hour as rL. In the figure, the mark Q indicates this example, and the mark indicates a comparative example in which ZrS2k was used as the main material for the positive electrode.
The charging and discharging characteristics in an environment of 0'C are significantly improved in this example.

<Example 2> As a positive electrode, MoS2 powder + RbCuaItsCJxs
Powder + Pd A battery was prepared under exactly the same conditions as in Example 1 above, except that a mixture of black powder and acetylene black in a weight ratio of 2:3:0.05:o, 1 was boiled for 60η. FIG. 3 shows the change in battery voltage over time when all 10 batteries were subjected to constant resistance load discharge at Ω and repeated charging. Both discharging and photocharging are repeated for 1 hour, and the ambient temperature is 80°C.
It was set to °C. In the figure, the circle mark indicates this example, and the mouth mark indicates ZrS2k.
This is a comparative example. Although Pd black powder and acetylene black were used here as the conductive material, all Pt black can be used instead of Pd black, and carbon powder such as acetylene black can also be added alone together with the solid electrolyte.

<Example 3> Positive electrode: MoTe2 +RbCu4I 1. s Cj
+x5 k mixed at a weight ratio of 2:3'r60yy
The battery completely exploded under the same conditions as in Example 1 above. Figure 4 shows the change in battery voltage over time when this battery '510 was subjected to two cycles of constant resistance load discharge at Ω and photovoltage. Both discharging and original charging were repeated for 1 hour, and the ambient temperature was 60°C. In the figure, the O mark is the result of this example, and the open mark is the result of the comparative example using Zr5zk.

In addition, the above positive electrode material MoX2 (where X is S or Ss.

Te) is a non-stoichiometric compound, which is MoXY
(1,6≦Y≦2.1), and it goes without saying that similar results can be obtained as long as the material is n-type.

Effects of the Invention As described above, in the present invention, by using a material mainly composed of MoXz k for the positive electrode, it was possible to eliminate the decomposition of the positive electrode during pre-charging at high temperatures.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the structure of a photovoltaic battery according to an embodiment of the present invention, FIGS. 2, 3, and 4 are diagrams showing the characteristics of a photovoltaic cell according to an embodiment of the present invention. FIG. 6 is a diagram showing the band structure of MoX2 and MoX2, and FIG. 6 is a diagram showing the principle of original charging. 1... Positive layer, 2... Solid electrolyte layer,
3... Negative electrode layer, 4... Transparent electrode, 5...
...Current collector, 6...Lead wire, 7...
... Sealed package, 8 ... Diode O Name of agent: Patent attorney Toshio Nakao and 1 other person 3-
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Claims (3)

[Claims] (1) A negative electrode mainly composed of copper, a Cu^+ ion conductive solid electrolyte, and an n-type MoX_2 (where X is S, Se, Te
1. A photo secondary cell comprising a positive electrode mainly composed of any one of the above, and is charged by irradiating the positive electrode with light. (2) The photo secondary battery according to claim 1, which uses a positive electrode of n-type MoX_2 (where X is S, Se, or Te, to which carbon powder and Cu^+ ion conductive solid electrolyte are added). (3) A photo secondary battery according to claim 1, which uses a positive electrode made of n-type MoX_2 (where X is S, Se, or Te, to which Pd or Pt powder and Cu^+ ion conductive solid electrolyte are added) .