JP2002235177A - SnO FILM AND PREPARING METHOD THEREFOR - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a polycrystal SnO film, and to provide a method for preparing the SnO film. SOLUTION: At first, SnF2 is dissolved in water to prepare an aqueous solution. This aqueous solution is sprayed on the surface of a base material 1s heated to 220 to 340 deg.C, so that an oxide thin film 1f consisting of a polycrystal SnO film can be prepared.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a SnO film and a method for producing the same.

[0002]

2. Description of the Related Art SnO films are known as p-type oxide semiconductors, and are particularly attracting attention as negative electrode materials for lithium ion secondary batteries. As a positive electrode material in a lithium ion secondary battery, lithium cobaltate, lithium nickelate, lithium manganate, or the like is used. Such an SnO film can be manufactured by a thermal evaporation method, an electron beam evaporation method, or a coating method. However, these manufacturing methods require a considerably large-scale operation such as a vacuum chamber.

[0003] Therefore, research has been conducted on the production of SnO films by spray pyrolysis. `` Journal of Power Source
s, vol. 87 (2000), pp. 106-111 ”(Literature 1) discloses formation of a tin oxide film by a spray pyrolysis method. In this method, first, a solution obtained by dissolving SnCl ₂ in water and adding acetic acid is prepared as a raw material solution.
Next, this raw material solution is sprayed on a stainless steel substrate heated to 350 ° C. According to the document, this method
This indicates that a tin oxide film (including Sn and O) in an amorphous state can be formed.

[0004] Also, "Journal of Material Research,
vol. 15 (2000), p. 1445-1448 ”(Reference 2) discloses a method for obtaining polycrystalline SnO powder. In this method, a hydrate of SnCl ₂ is dissolved in hydrochloric acid, ammonia is added thereto, and the mixture is allowed to stand until a white precipitate is formed. Thereafter, a reflux step is performed at 50 to 90 ° C., and the precipitate is filtered. And
By drying in vacuum, polycrystalline SnO and Sn
A powder made of a mixture of O ₂ is obtained. Where S
Since the color of the nO powder is black to brown and SnO ₂ is white, it is considered that the powder obtained by this method is mainly composed of SnO ₂ .

[0005]

[0005] However, Document 1
In the case where the spray pyrolysis method described in (1) is used, a polycrystalline SnO film cannot be obtained, and in the case where the method described in Document 2 is used, a small amount of polycrystalline SnO can be obtained. However, this is a SnO powder, not a SnO film.

The present invention has been made in view of the above problems, and has as its object to provide a polycrystalline SnO film and a method for producing an SnO film capable of obtaining the same.

[0007]

In order to solve the above-mentioned problems, a method for producing a SnO film according to the present invention comprises a step of producing a solution in which SnF ₂ is dissolved and a step of heating a substrate to 220 to 340 ° C. And a step of spraying the solution onto the surface of the heated substrate.

According to this method, a polycrystalline SnO film can be formed on a substrate. In other words, such a polycrystalline SnO film is formed on the surface of a substrate heated to 220 to 340 ° C. by spraying a solution of SnF ₂ on the substrate.

In some cases, SnF ₂ is hydrolyzed in the above solution to form a precipitate, but when this solution contains an acid, particularly acetic acid, the formation of a precipitate can be suppressed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will now be given of a SnO film according to an embodiment and a method of manufacturing the same. The same reference numerals are used for the same elements, and duplicate description will be omitted. First, a SnO film substrate having a SnO film will be described.

FIG. 1 is a vertical sectional view of the SnO film substrate 1. The SnO film substrate 1 is made of the oxide thin film 1f according to the embodiment.
Is formed on a base material (substrate) 1s. In this example, the substrate 1s is a glass substrate, and the oxide thin film 1f is tin (S
This is a SnO (stannic oxide) film containing n) and oxygen (O).

SnO is a compound of Sn and O, and the crystalline state of SnO in this example is polycrystalline.

The oxide thin film 1f may contain a trace amount of impurities. Examples of such impurities include C, Na, and Fe mixed in the manufacturing process, and B, Al, Ga, and I added for controlling the conductivity of the oxide thin film 1f.
n, Li, Na, K and the like.

The thickness of the oxide thin film 1f can be set arbitrarily.

Glass can be used as the material of the substrate 1s, but a dielectric material having low reactivity with Sn and O can be used instead. As a material that can be used instead of glass, for example, aluminum oxide can be given. When used as an electrode material for a secondary battery, a material having electrical conductivity is preferable as the material of the substrate 1s, and examples thereof include Al, Fe, Cu, and Au. In particular, when the substrate 1s is in the form of a thin film, it can be wound.

Next, an apparatus for manufacturing the oxide thin film 1f will be described.

FIG. 2 is a schematic view of an apparatus for manufacturing the oxide thin film 1f.

This manufacturing apparatus includes a substrate holder 2 on which a substrate 1s is installed, a heating device (hot plate) 3 for heating the substrate holder 2, and a raw material solution (L) on the surface of the substrate 1s. The spray gun 4 arranged above the base material 1s so as to be sprayed, the raw material tank 5 for storing the solution L to be supplied to the spray gun 4, and the raw material tank 5 and the spray gun 4 are connected to connect the raw material tank 5 to the spray gun 4. A pipe 45 for transferring the solution L is provided.

Further, the manufacturing apparatus supplies a compressed gas (A) to the spray gun 4, and connects the compressor 6 and the spray gun 4 with the compressor 6 for atomizing the solution L supplied thereto. A pipe 46 for sending the compressed gas A from the compressor 6 to the spray gun 4;
Is provided with an outer wall 7 surrounding the lateral periphery of the base material 1s so as not to scatter around.

Next, the oxide thin film 1 using the above manufacturing apparatus
A method for manufacturing f will be described.

The oxide thin film 1f is formed by sequentially performing the following steps. This manufacturing method is a spray pyrolysis method.

Compound (X) is a solvent (Q)
A solution L dissolved therein is prepared. The prepared solution L is supplied into the raw material tank 5.

The substrate 1s is placed in an atmosphere of normal pressure containing oxygen (referred to as B), and the heating device 3 heats the substrate 1s. This arrangement is performed by fixing the base material 1 s to the base material holder 2.

The solution L is sprayed from the spray gun 4 onto the surface of the substrate 1s heated to the temperature T through the atmospheric pressure atmosphere B to form an oxide thin film 1f containing SnO on the substrate 1s. . After spraying the solution L, the base material 1s is naturally cooled, but may be cooled at a cooling rate equal to or lower than the natural cooling rate.

In the above-described solution preparation step, the concentration C of the solution L is set between 0.002 and 0.4 M, and the growth rate of the oxide thin film 1 f varies according to the concentration C. The density C is set appropriately.

In the step of spraying the solution L from the spray gun 4, first, the solution L is supplied from the raw material tank 5 to the spray gun 4 via the pipe 45, and then the spray gun is supplied from the compressor 6 via the pipe 46. 4 is supplied with compressed gas A. The atmosphere B interposed between the surface of the base material 1s and the spray gun 4 is air in this example, and the compressed gas A supplied from the compressor 6 to the spray gun 4 is also air. Air is a mixed gas of oxygen gas and nitrogen gas.

By the time the solution L in the form of a mist reaches the surface of the substrate 1s, the solution L comes into contact with oxygen, is heated near the surface of the substrate 1s, and tin and oxygen combine to form a solution. Crystal S
The oxide thin film 1f made of nO is deposited on the surface of the substrate 1s.

The compound X, the solvent Q, the compressed gas A, the atmosphere B, and the temperature T during production are preferably as follows.

[0029]

[Table 1]

According to the findings of the present inventors, there is no known method for obtaining a thin film itself containing polycrystalline SnO.

As described above, the above-described method for producing the SnO film includes a step of producing a solution L in which SnF ₂ is dissolved, a step of heating the substrate 1 s to 220 to 340 ° C.
And a step of spraying the solution L onto the surface of the heated substrate 1s. According to this method, a polycrystalline SnO film can be formed on the substrate 1s.

In other words, such a polycrystalline SnO film is formed on the surface of the substrate 1s by spraying a solution of SnF ₂ on the substrate heated to 220 to 340 ° C. It is.

In some cases, SnF ₂ is hydrolyzed in the solution L to form a precipitate. When the solution L contains an acid, in particular, CH ₃ COOH (acetic acid), the formation of the precipitate may occur. Can be suppressed. When such an acid is not used, the precipitate is removed from the solution L by filtration, and then the spraying step (spraying) is performed. Also,
The concentration of acetic acid in the solution L is, for example, 0.1 to 10% by weight.
Is set between

Here, the compound (solute) X used for preparing the solution L, that is, SnF ₂ will be described.

In the above-mentioned references 1 and 2, SnO
Is manufactured using SnCl ₂ . However, when SnCl ₂ is used instead of SnF ₂ as a solute in the manufacturing method according to the above-described embodiment, only SnO ₂ can be finally manufactured.

This phenomenon was studied diligently. The cause of this phenomenon is that at a temperature (350 ° C. or higher) required to sufficiently cause the thermal decomposition of SnCl ₂ , the formed SnO is easily and strongly oxidized, and the amorphous SnO 2
Probably because it becomes ₂ .

Therefore, in order to suppress the oxidation of SnO, it is preferable that at least the substrate temperature T is 340 ° C. or less.

As a solute, SnF ₂ was used instead of SnF _2.
When F ₄ is used, its oxidation number is 4, so that only SnO ₂ can be obtained.

Further, even when SnF ₂ is used as the solute, it is necessary to provide energy necessary for the thermal decomposition of SnF ₂ and the combination of SnO, so that the substrate temperature T
Is set to 220 ° C. or higher. Since the oxidation of SnO also occurs when SnF ₂ is used as a solute, the substrate temperature T is 3
Set to 40 ° C or lower.

In this embodiment, a polycrystalline SnO film can be obtained by using SnF ₂ as a solute and setting the substrate temperature T at 220 ° C. to 340 ° C.

FIG. 3 is a longitudinal sectional view of a trial lithium ion secondary battery using the above-mentioned oxide thin film 1f.

A separator 11 is interposed between a negative electrode made of the SnO film substrate 1 and a positive electrode 10 made of a lithium composite compound, and these are immersed in an electrolytic solution 13 filled in a container 12. The SnO film substrate 1 constituting the negative electrode includes an oxide thin film 1f using polycrystalline SnO as an active material,
And a base material 1s using a Cu foil as a current collector. The positive electrode 10 includes a thin film 10f using a lithium composite compound such as lithium cobaltate, lithium nickelate or lithium manganate as an active material, and a base material 10s using an Al foil as a current collector. The separator 11 is made of a polyethylene porous membrane or the like. Note that various materials other than SnO can be used.

FIG. 4 is a longitudinal sectional view of the prismatic lithium ion secondary battery. In this secondary battery, a laminated sheet formed by laminating a negative electrode (1), a separator 11, a positive electrode 10, and a separator 11 'is spirally wound, and an electrolytic solution 13 in a container 12 is wound.
Immersed in an insulating plate 14
The opening is hermetically sealed with a sealing plate 15 with the intermediary of. A negative electrode terminal 16 is provided on the sealing plate 15, and a positive electrode terminal 17 is provided on the bottom of the container 12.

[0044]

EXAMPLES The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to the following examples. In the following experimental examples, polycrystalline Sn
The method in which O was formed is taken as an example, and the others are taken as comparative examples. (Experimental Example 1) An oxide thin film 1f having the structure shown in FIG. 1 was produced by using the spray pyrolysis method described above. That is, the solvent Q
A raw material solution L is prepared by dissolving a raw material X therein,
While heating the base material 1s at the temperature T, the raw material solution L is sprayed from the ejection port of the spray gun 4 onto the surface of the base material 1s via the atmosphere B, so that the raw material is reacted on the surface of the base material 1s. Then, an oxide thin film 1f containing SnO was formed. The experimental conditions at the time of fabrication are shown below.

[0045]

[Table 2]

The solution supply speed is the volume of the raw material solution ejected from the spray gun 4 per one spray, and the spraying (spraying) time is the raw material solution L for the base material 1 s.
And the number of times of spraying is the number of times the raw material solution is sprayed on the base material 1s. The distance between the spray port substrates is a distance from the spray gun 4 to the surface of the base material 1s. (Experimental example 2-Experimental example 36) (Experimental conditions) The concentration C, the substrate temperature T and / or the additive S in Experimental example 1 were changed as shown in the following table, and the other conditions were the same as in Experimental example 1 and the oxides were changed. A thin film 1f was manufactured.

[0047]

[Table 3]

(Results and Evaluation) Experimental Examples 1 to 36
When the raw material solution L is sprayed on the base material 1 s according to the experimental conditions of the above, SnF ₂ in the raw material solution is decomposed, reacted and oxidized,
An oxide thin film 1f was obtained on the substrate 1s.

FIGS. 5 to 8 are graphs showing X-ray diffraction spectra of the oxide thin films 1f obtained in Experimental Examples 1 to 36. The number displayed at the left end of the spectrum shown in each graph corresponds to the number of the experimental example.

The X-ray diffraction angles of SnO and SnO ₂ are shown in the following table.

[0051]

[Table 4]

Further, the following table shows the results of determination of the crystal state of the oxide thin film 1f based on the experimental examples and FIGS. In this table, circles indicate that the oxide thin film 1f is polycrystalline SnO.
Triangles indicate that crystals other than polycrystalline SnO are mixed, and crosses indicate polycrystalline SnO.
Indicates that O is not included.

[0053]

[Table 5]

FIG. 9 is a graph summarizing the judgment results of this table.

As described above, by appropriately adjusting the concentration C, an oxide thin film 1f containing polycrystalline SnO could be obtained at a temperature T of 220 ° C. or more and 340 ° C. or less.

When the concentration C is 0.08 M or less, an oxide thin film 1f containing polycrystalline SnO can be obtained at a temperature T of 240 ° C. or more and 320 ° C. or less.
At 260 ° C. or more and 300 ° C. or less, an oxide thin film 1f containing polycrystalline SnO as a main component could be obtained.

As described above, a solution in which SnF ₂ is dissolved is prepared, the base material 1s is heated to 220 to 340 ° C., and the solution L is sprayed on the surface of the heated base material 1s. With the probability, the polycrystalline SnO film could be manufactured as the oxide thin film 1f.

[0058]

According to the method of the present invention, polycrystalline SnO
It is possible to obtain a film.

[Brief description of the drawings]

FIG. 1 is a vertical sectional view of a SnO film substrate 1. FIG.

FIG. 2 is a schematic view of an apparatus for manufacturing an oxide thin film 1f.

FIG. 3 is a longitudinal sectional view of a trial lithium ion secondary battery using an oxide thin film 1f.

FIG. 4 is a longitudinal sectional view of a prismatic lithium ion secondary battery.

FIG. 5 is a graph showing an X-ray diffraction spectrum of an oxide thin film 1f.

FIG. 6 is a graph showing an X-ray diffraction spectrum of an oxide thin film 1f.

FIG. 7 is a graph showing an X-ray diffraction spectrum of the oxide thin film 1f.

FIG. 8 is a graph showing an X-ray diffraction spectrum of the oxide thin film 1f.

FIG. 9 is a graph summarizing the determination results of the crystal state.

[Explanation of symbols]

Reference Signs List 1 ... SnO film substrate, 1s ... base material, 1f ... oxide thin film, 2
... Substrate holder, 3 ... Heating device, 4 ... Spray gun, 5
... raw material tank, 6 ... compressor, 7 ... outer wall, 10s
... Base material, 10 ... Positive electrode, 10f ... Thin film, 11 ... Separator, 12 ... Container, 13 ... Electrolyte, 14 ... Insulating plate, 15 ...
Sealing plate, 16: negative terminal, 17: positive terminal, 45: piping, 46: piping.

Claims (3)

[Claims] 1. A method comprising: preparing a solution in which SnF ₂ is dissolved; heating a substrate to 220 to 340 ° C .; and spraying the solution on the surface of the heated substrate. A method for manufacturing a SnO film, which is a feature. 2. The method according to claim 1, wherein the solution contains acetic acid. 3. A polycrystalline SnO film formed on the surface of a substrate heated to 220 to 340 ° C. by spraying a solution of SnF ₂ on the substrate.