JPH08106902A - Thin film electrode for battery and its manufacture - Google Patents

Abstract

PURPOSE: To efficiently manufacture at low cost a battery with high charge/ discharge performance by forming an active material thin film deposited on the surface of a carrier in liquid phase reaction by sintering. CONSTITUTION: A mixed solution is prepared by adding an acid to a solution containing an active material made of a specified metal. A carrier of a specified metal is immersed in the mixed solution. An active material thin film with a specified thickness is deposited on the surface of the carrier in liquid phase reaction. The carrier is taken out from the mixed solution, and baked in the air at specified temperature. An electrode without peeling off from the carrier, with uniform thin film, large discharge capacity can be manufactured.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a thin film electrode for a battery, in particular,
The present invention relates to an active material for a lithium primary or secondary battery or a solar cell and a method for producing the same.

[0002]

2. Description of the Related Art Generally, as an electrode of a lithium battery,
Add a carbon-based conductive agent and a binder to the active material and mix,
The mixture is formed into a sheet or pressed onto a current collector such as a mesh as a positive electrode, metallic lithium is used as a negative electrode active material, and this is pressed onto a current collector such as nickel or stainless steel. Has been adopted.

[0003]

However, in the electrode having the above structure, the electrolytic solution must be additionally added by adding a conductive agent, a binder or the like, and the battery performance by addition of other than the active material is also increased. The impact on Moreover, since the volume of the electrode is increased by the addition of the conductive agent, the binder, etc., the packing density of the active material is lowered, which inevitably causes the battery capacity per unit weight to be lowered. On the other hand, when the electrode is formed only of the powdered active material to which no conductive agent or binder is added, the capacity per unit weight becomes large, but the mechanical strength of the electrode is lowered, and the secondary battery that is charged and discharged is charged. In this case, there is a problem that the crystal structure changes such as shrinkage and expansion of the crystal due to charge and discharge, resulting in separation from the current collector and deterioration of performance as the charge and discharge cycle increases. Therefore, it is possible to use an ultra-thin film forming method such as a chemical vapor deposition method as an electrode forming method, but this method requires a high temperature for the reaction, the atmosphere is difficult to control, mass production cannot be performed, and the cost is low. There are problems such as high price.

Therefore, according to the present invention, a battery having excellent charge and discharge characteristics can be manufactured at a low cost, which is formed of only an active material and does not peel off from a current collector or a carrier when applied to a primary or secondary battery. The purpose is to obtain a possible electrode. Another object of the present invention is to make it possible to inexpensively and efficiently manufacture an electrode made of only an active material.

[0005]

As a means for achieving the above object, the present invention comprises an electrode formed of a metal oxide thin film deposited on the surface of a carrier by a liquid phase reaction.

As the carrier, metals such as stainless steel, aluminum, copper and nickel, ceramics, synthetic resins and the like can be used, and these can be used for plates, films,
Any form such as a foil or a screen can be adopted.

Regarding the active material, in the case of a primary battery,
As the positive electrode active material, any conventionally known material can be used, but typical examples thereof include metal oxides, sulfides such as copper sulfide, halides such as fluorinated graphite, and composite oxides such as silver chromate. Can be given. In the case of a secondary battery, as the positive electrode active material, in addition to metal oxides or composite oxides, transition metal dichalcogenides represented by the general formula: MX ₂ such as TiS ₂ and MoS ₂ , NbSe _{3 and the} like are generally used. Formula: MX ₃
The transition metal trichalcogenide represented by the formula (1) and the like are mentioned, but it is preferable to use an oxide or a composite oxide. Fe ₂ O ₃ , MnO ₂ , CuO is used as the oxide-based active material.
₂ , V ₂ O ₅ , V ₆ O ₁₃ , LiOH-MnO ₂ , Li _x NiO
_y (x = 0 to 1.5, y = 1 to 2) and Li _x Mn ₂ O ₄ (x
= 0-2) is preferably used.

In a preferred embodiment, the thin film of active material on the surface of the carrier is set to have a thickness of 5 μm or less.

In the thin film electrode according to the present invention, a metal hydroxide constituting an active material is deposited on the surface of a carrier by a liquid phase reaction to form a thin film, and the thin film is in air at 300 to 500 ° C.
It can be manufactured by firing at.

The liquid phase reaction is preferably carried out by adding an acid to a solution containing a metal fluoride as an active material and immersing the carrier in the mixed solution. In this case, the deposition temperature is 20
It is desirable to maintain ~ 35 ° C. A typical acid is boric acid.

[0011]

In the electrode according to the present invention, the active material has a true specific gravity of 10 to 10
Since it is a uniform thin film with a packing density in the range of 90%, it does not peel off from the carrier that functions as a current collector even when it is repeatedly used as an electrode of a secondary battery, and the cycle life is significantly improved. Further, since the thin film is made of only the active material without containing a conductive agent or a binder, the mechanical strength is increased, the capacity per unit weight is increased, and the charge / discharge characteristics are improved. Further, according to the present invention, when the carrier is immersed in a thin film forming bath, a thin film having a cotton-like structure is formed on the surface thereof, and the active material thin film is formed by baking the thin film. The electrode forming operation can be continuously performed at a low temperature, and an electrode having a large area can be formed.

[0012]

Example 1 FeCl ₃ was used as a starting material, and this was dissolved in water to prepare a 0.1 M aqueous solution, which was kept at a temperature range of 60 to 90 ° C. for 2 hours to precipitate iron oxyhydroxide (FeOOH). It was The reaction solution was evaporated to dryness to obtain a precipitate (Fe
OOH) was obtained, and this was added to an aqueous solution of ammonium hydrogen fluoride at 30 ° C. in a molar concentration ratio of FeOOH: NH4F · HF = 1: 5.
Was added to dissolve it as iron fluoride, and 0.5 mol of H ₃ BO ₃ was added to the solution to prepare a thin film forming bath. A stainless steel substrate is immersed in this bath as a carrier and kept in a constant temperature bath at 27 ° C. for several hours to obtain FeO each having a thickness of 1 to 3 μm.
An OH thin film was deposited. Then, the stainless steel substrate was taken out of the bath and baked in air at 300 to 500 ° C. for 3 hours to obtain an electrode using Fe ₂ O ₃ as an active material.

The obtained electrode was dried under reduced pressure and then Fe ₂
A cell (button-type battery-R2025) having O ₃ 0.47 mg / cm ² as a positive electrode active material was assembled. As the electrolytic solution, an aprotic organic electrolytic solution prepared by dissolving lithium perchlorate (LiClO ₄ ) in a mixed solvent of propylene carbonate (PC) and 1,2-dimethoxyethane (DME) at a volume ratio of 1: 1 was used. .

The characteristics of the cell as a primary battery and a secondary battery, that is, the voltage-capacity characteristics were measured. The results are shown in FIGS. 1 and 2. Figure 1 shows the voltage-capacity characteristics of a primary battery with a discharge current density of 0.044 mA / mm.
² (solid line) and 0.5 mA / mm ² (dashed line) were evaluated. Figure 2 shows a voltage-to-capacitance characteristics when a secondary battery, the discharge current density 0.044mA / mm ² (solid line) was evaluated respectively as 0.5 mA / mm ² (dashed line).

As is apparent from FIGS. 1 and 2, according to the present invention, it is understood that the voltage-capacity characteristics that can be put to practical use can be obtained for both the primary battery and the secondary battery.

Next, with respect to the cells of the secondary battery, the charging / discharging current density was 0.5 mA / cm ² (5.6 C: charged in 11 minutes, 11
Discharge) and a charge / discharge potential width of 2.0 to 0.0 V was evaluated. The obtained results are shown in FIG. 3 together with the results of the comparative example.

[0017] In Comparative Example 1 that uses only the active material Fe ₂ O ₃ on a stainless substrate spin-coated electrodes (thickness 8 [mu] m) as a positive electrode, Comparative Examples 2 and 3, the active material Fe ₂
A molded electrode obtained by adding acetylene black as a conductive agent to O ₃ and a fluorine resin as a binder was used as a positive electrode. Comparative Example 2 was a comparative example when the charge / discharge current density was 0.05 mA / cm ^2. No. 3 is the result when the charge / discharge current density is 0.5 mA / mm ² .

From the results shown in FIG. 3, it can be seen that the cell using the electrode according to the present invention has a remarkably large discharge capacity as compared with the cell of the comparative example, and the deterioration with charging / discharging cycle is remarkably small.

[0019]

Example 2 Next, an example of using the electrode of the present invention in a solar cell will be described. Using the thin film forming bath of Example 1,
Immerse transparent conductive glass as a carrier in this bath at 27 ° C
The FeOOH was deposited by holding the same in a constant temperature bath for several hours.
Then, the transparent conductive glass is taken out of the bath and placed in air for 3
It was fired at 00 to 500 ° C. for 3 hours to obtain an electrode using Fe ₂ O ₃ as an active material. Note that SnO ₂ glass containing fluorine was used as the transparent conductive glass. After drying the obtained electrode under reduced pressure, a solar cell having a structure shown in FIG. 4 was manufactured.
In the figure, 1 is transparent conductive glass, 2 is α-Fe with a film thickness of 5 μm
₂ O ₃ electrode, 3 insulator, 4 electrolyte of tetra-n-butyl-ammonium perchlorate 0.1M in acetonitrile added with 0.5 mM ruthenium bipyridine, 5 a platinum plate, The cell area is 1 cm ² .

Light (A) 250 W / m ² and (B) 1 KW / m ² were made to enter the obtained solar cell from the transparent conductive glass side, and the voltage-current characteristics were measured. The result is shown in FIG. From FIG. 5, it can be seen that the electrode of the present invention can be used as an electrode of a solar cell.

In the above examples, oxide-based Fe ₂ O ₃ , MnO _{2 and the} like were exemplified as the active material, but NiO _y (y
= 1 to 2) or a MnO ₂ thin film is formed, and Li ⁺ is electrochemically inserted after that to form Li _x Ni _{0 y} (x ≦ 1.
5, y ≦ 1-2) and Li _x Mn ₂ O ₄ (x ≦ 2), and these can be used as the active material thin film.

[0022]

As is apparent from the above description, according to the present invention, since the packing density of the active material is high, peeling from the carrier does not occur, and even when it is used as an electrode of a secondary battery, it does not cause a charge / discharge cycle. It is possible to suppress the accompanying deterioration and obtain a battery having a large discharge capacity because it is formed as a uniform thin film. Further, according to the present invention, since the electrodes can be formed by a liquid phase reaction and can be performed at a low temperature, an excellent effect that an electrode having a large area can be continuously produced can be obtained.

[Brief description of drawings]

FIG. 1 is a voltage capacity characteristic diagram of a cell of a primary battery using the electrode of the present invention.

FIG. 2 is a voltage capacity characteristic diagram of a cell of a secondary battery using the electrode of the present invention.

FIG. 3 is a charge / discharge characteristic diagram of a cell using the present invention and a conventional electrode.

FIG. 4 is a schematic explanatory view showing a structure of a solar cell using the electrode of the present invention.

5 is a voltage-current characteristic diagram of the solar cell shown in FIG. 4 using the electrode of the present invention.

[Explanation of symbols]

 1 Transparent conductive glass 2 Thin film electrode 3 Insulator 4 Electrolyte 5 Platinum plate

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location H01M 4/58 4/66 A

Claims (8)

[Claims] 1. A thin film electrode for a battery comprising an active material thin film deposited on the surface of a carrier by a liquid phase reaction. 2. The thin film electrode for a battery according to claim 1, wherein the carrier is one of metal, ceramics and synthetic resin. 3. The thin film electrode for a battery according to claim 1, wherein the carrier is one selected from the group consisting of stainless steel, aluminum, copper and nickel. 4. The active material is a metal oxide, a sulfide, a halide, a composite oxide, a transition metal dichalcogenide represented by the general formula: MX ₂ and a transition metal trichalcogenide represented by the general formula: MX _3. The thin film electrode for a battery according to claim 1, which is one selected from the group consisting of: 5. The active material is Fe ₂ O ₃ , MnO ₂ , Cu.
O ₂ , V ₂ O ₅ , V ₆ O ₁₃ , LiOH-MnO ₂ , Li _x NiO _y
(X = 0 to 1.5, y = 1 to 2) and Li _x Mn ₂ O ₄ (x
= 0 to 2), which is a kind selected from the group consisting of
The thin film electrode for a battery according to any one of 1 to 3. 6. The thin film electrode for a battery according to claim 1, wherein the thin film is a thin film having a thickness of 5 μm or less. 7. A battery characterized in that a metal hydroxide constituting an active material is deposited on a surface of a carrier by a liquid phase reaction to form a thin film, and the thin film is baked in air at 300 to 500 ° C. Method for manufacturing thin film electrode. 8. The method for producing a thin film electrode for a battery according to claim 7, wherein the liquid phase reaction is carried out by adding an acid to a solution containing a metal fluoride serving as an active material and immersing the carrier in the mixed solution. .