JP7486732B2 - Method for producing nickel hydroxide thin film - Google Patents

Description

The present embodiment relates to a method for producing a nickel hydroxide thin film .

Conventionally, secondary batteries have been proposed that do not use electrolyte or rare elements and can be made thin, so they are made of a stack of a first electrode, an insulator, an n-type oxide semiconductor layer, a p-type oxide semiconductor layer, and a second electrode.

Also, as a structure similar to this secondary battery, a secondary battery has been proposed that has a positive electrode with a positive electrode active material film containing nickel oxide or the like as a positive electrode active material, a solid electrolyte with a water-containing porous structure, and a negative electrode with a negative electrode active material film containing titanium oxide or the like as a negative electrode active material.

Furthermore, secondary batteries have been proposed that use nickel oxide as the positive electrode active material, titanium oxide formed by sputtering as the negative electrode active material, and metal oxides such as silicon oxide as the solid electrolyte.

On the other hand, methods for forming films at low temperatures while maintaining hydroxide state include the advection deposition method and the dip method.

In addition, methods for depositing a film on a substrate using non-vacuum deposition techniques include air-open solution-based deposition methods such as the spray method, the sol-gel method, and the mist CVD (Chemical Vapor Deposition) method.

The mist CVD method is a method in which a solution containing the main component is atomized into a mist and then supplied to the substrate in the mist state. By controlling the mist supply conditions and designing the reactor, it is possible to manufacture thin films with a high degree of uniformity. In addition, the mist CVD method has a low environmental impact and low operating costs.

JP 2019-71479 A JP 2019-33142 A JP 2018-76591 A Japanese Patent No. 5508542 Patent No. 5297809 JP 2015-82445 A JP 2016-82125 A JP 2017-147186 A

In a thin-film solid-state secondary battery that uses nickel hydroxide for the positive electrode and titanium oxide for the negative electrode, a method has been proposed in which nickel oxide is first formed into a film by sputter deposition, and then nickel hydroxide for the positive electrode is formed by electrical treatment. A problem with this method is that it is difficult to form a thick positive electrode.

In the present embodiment, a method for producing a nickel hydroxide thin film is provided in which the film thickness is approximately uniform and can be easily controlled by adjusting the mist spray time.

According to one aspect of the present embodiment, there is provided a method for producing a nickel hydroxide thin film, comprising the steps of: preparing a dispersion liquid in which nickel hydroxide nanoparticles (in the present invention, "nanoparticles" refers to particles having a size on the order of several hundred nanometers or less) are dispersed; converting the dispersion liquid into a mist using ultrasound; transporting the mist containing the nickel hydroxide nanoparticles using an inert gas; spraying the mist containing the nickel hydroxide nanoparticles onto a substrate through a nozzle; evaporating the mist on or directly above the substrate; and depositing the nickel hydroxide nanoparticles dispersed in the mist on the substrate to form a film of nickel hydroxide (Ni(OH) ₂ ) on the substrate.

According to another aspect of the present embodiment, there is provided a method for producing a nickel hydroxide thin film, comprising a first step of preparing a dispersion liquid in which nickel hydroxide nanoparticles are dispersed in a first container, a second step of misting the dispersion liquid with ultrasonic waves to prepare a nickel hydroxide solution mist containing nickel hydroxide nanoparticles, a third step of transporting the nickel hydroxide solution mist with an inert gas, and a fourth step of discharging the nickel hydroxide solution mist transported in the third step onto a heated substrate.

According to another aspect of the present embodiment, there is provided a method for producing a nickel hydroxide thin film, comprising the steps of: forming a mist from a dispersion liquid in which nickel hydroxide nanoparticles are dispersed in a first container to obtain a nickel hydroxide solution mist; transporting the nickel hydroxide solution mist through a mist path with a first inert gas; receiving the nickel hydroxide solution mist in a classifier disposed downstream of the mist path; and discharging the nickel hydroxide solution mist from the classifier onto a heated substrate.

According to another aspect of the present embodiment, a method for producing a nickel hydroxide thin film is provided, which includes the steps of: forming a mist from a dispersion liquid in which nickel hydroxide nanoparticles are dispersed in a first container to obtain a nickel hydroxide solution mist; forming a metal compound mist from a metal compound solution containing a metal compound in a second container independent of the first container; mixing the nickel hydroxide solution mist and the metal compound mist in a mixing container that receives the nickel hydroxide solution mist and the metal compound mist via first and second paths independent of each other to obtain a mixed mist; and discharging the mixed mist from the mixing container via a third path onto a heated substrate to form a film of nickel hydroxide mixed with a metal oxide on the substrate.

According to this embodiment, it is possible to provide a method for manufacturing a nickel hydroxide thin film in which the film thickness is approximately uniform and the film thickness can be easily controlled by adjusting the mist spray time.

FIG. 1 is a schematic diagram showing the configuration of a first manufacturing apparatus applicable to a method for manufacturing a nickel hydroxide thin film according to an embodiment of the present invention. An example of measuring the step height on the surface of a thin nickel hydroxide film made from a dispersion of nickel hydroxide particles dispersed in water. An example of measuring the step height on the surface of a thin nickel hydroxide film made from a dispersion of nickel hydroxide particles in ethanol. The results of measuring the film thickness and in-plane distribution of the film thickness as a function of stage temperature for a nickel hydroxide thin film produced using a dispersion liquid containing nickel hydroxide nanoparticles of approximately 100 nm. 1 is a cross-sectional SEM photograph of a nickel hydroxide thin film formed under conditions of a carrier gas flow rate of 5.0 L/min and a diluent gas flow rate of 2.0 L/min in the nickel hydroxide thin film manufacturing method according to the present embodiment. FIG. 2 is a schematic diagram showing the configuration of a second manufacturing apparatus applicable to the method for manufacturing a nickel hydroxide thin film according to the present embodiment. The deposition conditions for forming a mixed thin film of cobalt hydroxide and nickel hydroxide. An example of a SEM-EDX photograph of the surface of a mixed thin film of zinc acetylacetonate and nickel hydroxide. 4 is an example of charge/discharge characteristics of a secondary battery having a positive electrode active material layer made of a nickel hydroxide thin film formed by the nickel hydroxide thin film manufacturing method according to the present embodiment. 1 is a schematic cross-sectional view of a secondary battery according to a first embodiment; (a) An example in which the negative electrode active material layer includes TiO _x and the positive electrode active material layer includes Ni(OH) ₂ ; (b) an example in which the negative electrode active material layer includes TiO _x and SiO _x and the positive electrode active material layer includes Ni(OH) ₂ . (a) A modification of Fig. 11 in which a buffer layer is inserted between the solid electrolyte and the positive electrode active material layer. (b) A modification of Fig. 11 different from 12(a). (a) A modification of Fig. 11 in which a buffer layer is inserted between the solid electrolyte and the negative electrode active material and between the solid electrolyte and the positive electrode active material layer. (b) A modification of Fig. 11 different from 13(a). (a) A modification of Fig. 11 in which a buffer layer is inserted between the solid electrolyte and the negative electrode active material layer. (b) A modification of Fig. 11 different from 14(a). (a) A modified example of Fig. 11 in which a buffer layer containing a metal oxide is inserted between the positive electrode active material layer and the solid electrolyte layer, and (b) a modified example of Fig. 11 in which a buffer layer containing a metal oxide is inserted between the negative electrode active material layer and the solid electrolyte layer. Specific examples of a negative electrode active material layer and a positive electrode active material in the schematic cross-sectional view illustrated in FIG. 10 . FIG. 11 is a schematic cross-sectional view of a secondary battery according to a second embodiment. FIG. 11 is a schematic cross-sectional view of a secondary battery according to a third embodiment.

[First Nickel Hydroxide Manufacturing Apparatus]
A schematic configuration of a first manufacturing apparatus 101 applicable to the manufacturing method of a nickel hydroxide thin film according to the present embodiment is shown in Fig. 1. The manufacturing apparatus 101 of nickel hydroxide according to the present embodiment has a nanoparticle mist injection manufacturing apparatus structure, and includes sprayers (150, 160), a classifier 80, and a film forming device section 110.

The sprayer (150, 160) includes a dispersion container 150 that contains a dispersion 140 in which nickel hydroxide nanoparticles are dispersed in pure water or the like, and a mist generator 160, and has the function of misting the dispersion containing nickel hydroxide nanoparticles to produce a nickel hydroxide solution mist. As shown in FIG. 1, a carrier gas G1 (first inert gas) is introduced into the sprayer (150, 160), and a nickel hydroxide solution mist containing nickel hydroxide nanoparticles (hereinafter, mist M1) is sent to the classifier 80 via a path L1 (mist path). In addition, a flow rate adjustment gas G2 (second inert gas) that adjusts the flow rate of the mist M1 in the path L1 may be introduced into the path L1.

As the flow rate adjusting gas G2, an inert gas that has no activity in the film forming process, such as nitrogen _N2 or argon Ar, is used, and preferably, the same type of gas as the carrier gas G1 is used.

In addition, it is desirable to provide a flow rate adjustment means such as a flow meter or mass flow controller in the introduction path of the flow rate adjustment gas G2, which can adjust the amount of the flow rate adjustment gas G2 introduced in order to set the mist concentration to a predetermined value or to change it appropriately, and further to change it during film formation.

The carrier gas G1 for carrying the mist M1 is preferably an inert gas that has no activity in the film forming process, such as nitrogen _N2 or argon Ar.

The classifier 80 has the function of retaining the mist M1 sent from the sprayer (150, 160) and reducing the weight distribution of the mist M3 sent to the nozzle 120. This is because the mist containing relatively large nickel hydroxide nanoparticles is trapped while retained in the classifier 80, so the mist M3 sent to the nozzle 120 can be narrowed down to one with a small particle size. The classifier 80 can also homogenize the inert gas (carrier gas G1, flow rate adjustment gas G2) introduced from the sprayer (150, 160).

The film forming device section 110 is composed of a nozzle 120 that sprays mist M3, a stage 130 that has the function of scanning the substrate 40 from side to side and a built-in heater that can heat the substrate 40 up to 400°C. The substrate 40 for depositing nickel hydroxide is placed on the stage 130.

The mist M3 introduced from the classifier 80 is sprayed onto the substrate 40 placed on the stage 130. In order to stably spray the mist M3 onto the substrate 40, the nozzle 120 can change parameters such as the nozzle width, the distance to the substrate, and the nozzle temperature, and the various parameters are changed according to the film formation. The stage 130 can supply the amount of heat required to evaporate the sprayed mist M3. If the film formation temperature is low, the mist M3 turns into droplets on the substrate 40, causing surface abnormalities such as watermarks. On the other hand, if the film formation temperature is high, the mist M3 evaporates away from the substrate 40, and the nickel hydroxide nanoparticles are exhausted. In terms of temperature, it is optimal for the mist M3 to evaporate immediately after it reaches and contacts the substrate. The surface temperature of the substrate 40 also depends on the amount of mist M3 supplied.

[Method of manufacturing nickel hydroxide thin film]
The method for producing a nickel hydroxide thin film according to the present embodiment is a method for producing a nickel hydroxide thin film by using a mist as a transport means to send a mist M3 containing nickel hydroxide nanoparticles onto a substrate 40, evaporating the mist M3, and depositing the nickel hydroxide nanoparticles contained in the mist M3. The apparatus configuration required for this purpose is as shown in FIG.

In a method in which nickel hydroxide nanoparticles are mixed in a solvent, a substrate is immersed in the solution, and the solvent evaporates and disappears, causing precipitation and deposition on the substrate to form a film, or in a similar method in which a substrate is immersed in the solution and then pulled up at a constant speed to form a film, unevenness in the film thickness occurs when the solvent dries on the substrate, making it difficult to control the film thickness at the level of several tens to several hundreds of nm when forming a film at the submicron to micron level. In addition, depending on the film formation conditions, the substrate may be immersed in the solvent for a long time, and the underlying film on which the nickel hydroxide film is formed may be affected by the solvent, so there are limitations on the substrates on which the film can be formed. Furthermore, if there is variation in the particle size of the nanoparticles in the solvent, it tends to make it extremely difficult to control the flatness and film thickness distribution of the formed film.

The method for manufacturing a nickel hydroxide thin film according to this embodiment involves preparing a nickel hydroxide dispersion in which nickel hydroxide nanoparticles are dispersed, turning it into a mist using ultrasonic waves, transporting the nickel hydroxide solution mist containing the nickel hydroxide nanoparticles using an inert gas G1 and spraying it onto the substrate 40 through a nozzle 120 with a narrow gap, and evaporating the nickel hydroxide solution mist on or just above the substrate 40, thereby depositing the film-forming material (nickel hydroxide nanoparticles) contained in the mist onto the substrate 40 to form a film.

The nickel hydroxide thin film manufacturing method according to this embodiment allows deposition of nanoparticles without immersing the substrate in a solvent, increasing the variety of substrates on which films can be formed. In addition, the manufacturing method according to this embodiment can form a thin film of the hydroxide in the submicron to micron range with a variation of several tens to several hundreds of nanometers while maintaining its characteristics. Furthermore, the manufacturing method according to this embodiment can also be applied to a method for forming a thin film of nickel hydroxide, which is the positive electrode active material of secondary batteries.

The nickel hydroxide thin film manufacturing method according to this embodiment makes it possible to manufacture a secondary battery having nickel hydroxide in the positive electrode active material layer. The film thickness is approximately uniform, and the film thickness can be easily controlled by adjusting the mist spray conditions, and the positive electrode active material layer can also be easily made thicker.

This method suppresses the unevenness (watermarks) in the film that occurs when the solvent dries in the conventional method. In other words, with this method, nickel hydroxide nanoparticles are uniformly distributed on the substrate, making the film thickness more uniform than with conventional methods, and film thickness control easier by adjusting the mist spray conditions. In addition, because the particle diameter of the particles used in film formation is limited to those that can be contained within the mist, the particle diameter of the nanoparticles during film formation is uniform, resulting in improved film uniformity.

In this embodiment, it is possible to provide a method for manufacturing a nickel hydroxide thin film in which the film thickness is approximately uniform and the film thickness can be easily controlled by adjusting the mist spray conditions, and a secondary battery manufactured using this manufacturing method.

(Experiment 1)
A dispersion liquid in which nickel hydroxide nanoparticles are dispersed was prepared, and mist deposition was carried out to form a nickel hydroxide thin film using the manufacturing apparatus shown in Figure 1. As a result, a film thickness of 0.5 μm was confirmed, but the film had many irregularities on the surface.

(Experiment 2)
In the manufacturing method of the nickel hydroxide thin film according to the present embodiment, a dispersion liquid in which nickel hydroxide nanoparticles of about 100 nm are dispersed was prepared, and mist film formation was carried out to form a nickel hydroxide thin film using the manufacturing apparatus shown in Fig. 1. The measurement results of the film thickness and its in-plane distribution versus the film formation temperature (stage temperature) when forming the nickel hydroxide thin film are shown in Fig. 4.

In this experiment, a dispersion liquid containing distributed nickel hydroxide nanoparticles was prepared, and the relationship between the stage temperature and the uniformity of the nickel hydroxide growth film was investigated. As a result, there was a tendency for uniformity to improve as the stage temperature increased. Since nickel hydroxide decomposes at around 230°C, attention must also be paid to the uniformity of the temperature distribution on the substrate surface when deciding on a process. Naturally, the optimal temperature differs depending on the carrier gas flow rate, dilution gas flow rate, scan speed, etc.

(Experiment 3)
A dispersion liquid in which nickel hydroxide nanoparticles are dispersed was prepared by dispersing nickel hydroxide nanoparticles in water using the manufacturing apparatus shown in Figure 1. Figure 2 shows an example of measuring the step height on the surface of a thin nickel hydroxide film in this case. In Figure 2, the horizontal scale is represented by X (mm) and the vertical scale is represented by Z (μm).

Figure 3 shows an example of measuring the step height on the surface of a nickel hydroxide thin film produced by dispersing nickel hydroxide nanoparticles in ethanol using the production apparatus shown in Figure 1. In Figure 3, the horizontal scale is represented by X (mm) and the vertical scale is represented by Z (μm). Comparing Figures 2 and 3, it was found that when comparing the solvents methanol and water, methanol produced a film with a denser structure and better uniformity than water. The use of methanol also makes it possible to reduce the temperature during film formation. This is thought to be because methanol has better wettability and is more volatile than water.

(Experiment 4)
Using the manufacturing apparatus shown in Figure 1, a dispersion liquid in which nickel hydroxide nanoparticles are dispersed was prepared, and then misted to form a nickel hydroxide thin film on a substrate. Figure 5 shows an example of a cross-sectional SEM photograph of the nickel hydroxide thin film formed under conditions of a carrier gas flow rate of 5.0 L/min and a diluent gas flow rate of 2.0 L/min.

Next, for comparison, we compared the presence and absence of a classifier 80 that functions as a flow divider.

[First manufacturing apparatus without classifier 80]
When preparing a dispersion liquid using hydroxide nanoparticles having a small and uniform particle size, a mist M3 having a uniform particle size can be sent to the injection nozzle 120 without passing through the classifier 80. That is, in the first manufacturing apparatus that does not have the classifier 80, the dispersion liquid is not trapped by the classifier 80, so that the effective utilization rate of the dispersion liquid does not decrease.

[Second manufacturing apparatus having classifier 80 (FIG. 1)]
On the other hand, when preparing a dispersion using hydroxide nanoparticles with non-uniform particle sizes, a classifier 80 is required. However, passing through the classifier 80 reduces the film formation speed. When the flow rate of the mist carrier gas was increased to compensate for this, the film density tended to improve at the same film thickness. By passing through the classifier 80, the mist from which the large-sized nickel hydroxide nanoparticles have been removed is supplied to the nozzle 120. It is believed that narrowing the mist diameter distribution to small diameters contributes to increasing the film thickness uniformity and density of the nickel hydroxide thin film formed on the substrate. On the other hand, the effective utilization rate of the dispersion decreases.

[Third manufacturing apparatus 103]
As shown in FIG. 6 , a third manufacturing apparatus 103 applicable to the method for manufacturing a nickel hydroxide thin film according to the present embodiment is composed of a film-forming device section 110, a stage 130 for heating the film-forming device section 110, a dispersion liquid container 150 for accommodating a nickel hydroxide dispersion liquid 140, a mist generator 160 for turning the dispersion liquid 140 in the dispersion liquid container 150 into a mist to produce a nickel hydroxide solution mist, a dispersion liquid container 250 for accommodating a metal compound solution 240 containing a metal compound, a mist generator 260 for turning the metal compound solution 240 in the dispersion liquid container 250 into a mist, and a mixing container 90.

In this configuration, mist M1 produced from the dispersion liquid 140 by the mist generator 160 is supplied to the mixing vessel 90 via path L1. On the other hand, metal oxide mist (hereinafter, mist M2) produced from the metal compound solution 240 by the mist generator 260 is supplied to the mixing vessel 90 via path L2, which is provided independently of path L1.

Mist M1 and mist M2 supplied to the mixing container 90 via paths L1 and L2 are mixed in the mixing container 90 and supplied to the nozzle 120 via path L4 as mixed mist M4, which is then sprayed onto the substrate 40 to form a thin film of nickel hydroxide containing metal oxide on the surface of the substrate 40.

That is, with the substrate 40 placed on the stage 130, the mixed mist M4 is supplied under atmospheric pressure, and a thin film of nickel hydroxide containing the additive is formed on the substrate 40.

The dispersion container 150 is filled with the dispersion 140, which is the material solution for forming the nickel hydroxide thin film. This dispersion 140 is a material solution in which nickel hydroxide nanoparticles are dispersed in a solvent. The solvent may be water, methanol, or the like. Here, the nickel hydroxide nanoparticles can be produced, for example, by using a neutralization titration method.

The mist generator 160 may be, for example, an ultrasonic atomizer. The mist generator 160, which is an ultrasonic atomizer, applies ultrasonic waves to the dispersion liquid 140 in the dispersion liquid container 150, thereby turning the dispersion liquid 140 in the dispersion liquid container 150 into a mist. The mist M1, which is the mist of the dispersion liquid 140, is supplied into the mixing container 90 through a path L1.

A metal compound solution 240 for Ni element is filled in the dispersion liquid container 250. For example, a Ni acetylacetonate (Ni(acac) ₂ ) solution can be used as the metal compound solution 240.

The mist generator 260, which has the same function as the mist generator 160, applies ultrasonic waves to the metal compound solution 240 in the dispersion liquid container 250 to turn the metal compound solution 240 in the dispersion liquid container 250 into mist, creating mist M2. The mist M2 is supplied into the mixing container 90 through path L2.

When mist M1 and mist M2 are supplied into the mixing container 90 via different paths L1 and L2, the mist M1 and mist M2 are mixed in the mixing container 90 to generate a mixed mist M4. The mixed mist M4 is supplied to the nozzle 120 via path L4. The mixed mist M4 is supplied from the nozzle 120 onto the substrate 40.

As a result, the mixed mist M4 evaporates on the substrate 40 heated under atmospheric pressure, and a thin film of nickel hydroxide containing metal oxide is formed on the substrate 40. Note that the substrate 40 may be, for example, an unfinished solid-state secondary battery on which no positive electrode active material has been formed.

(Experiment 5)
In experiment 5, a method for depositing a plurality of nanoparticles was carried out using a third manufacturing apparatus 103 utilizing a mixing vessel 90 shown in Fig. 6. For example, a method for producing a nickel hydroxide film and a nickel oxide (NiO) film using a combination of nickel oxide nanoparticles was carried out. Also, a method for producing a mixed film of cobalt hydroxide and nickel hydroxide was carried out.

The method uses two dispersion solution containers (150, 250) and a mixing container to form a mixed film of two substances. The method will be explained using a combination of a first sprayer (150, 160) and a second sprayer (250, 260).

A dispersion of nickel hydroxide nanoparticles is put into the first sprayer, and a metal compound solution of cobalt hydroxide nanoparticles is put into the second sprayer, which is then turned into mist and sent to the mixing vessel 90. When a film was formed using the mixed mist M4, a mixed film of cobalt hydroxide and nickel hydroxide was formed. Furthermore, it was confirmed that a mixed film in which the two substances are mixed in any ratio can be formed by changing the flow rate ratio of the carrier gas of each of the first sprayer and the second sprayer.

In the manufacturing method of a nickel hydroxide thin film according to the present embodiment, a metal compound solution of cobalt hydroxide nanoparticles is fed into the second sprayer of the manufacturing apparatus of FIG. 6 , and a dispersion liquid of nickel hydroxide nanoparticles is fed into the first sprayer, which are turned into mist and sent to mixing container 90, respectively. The flow rate conditions of the carrier gas and dilution gas when the mixed mist M4 is used to form a mixed film of cobalt hydroxide and nickel hydroxide are shown in FIG. 7 .

In condition 1, the flow rate of the carrier gas for the metal compound solution of cobalt hydroxide nanoparticles was set to 5 L/min, and the flow rate of the flow rate adjustment gas was set to 2 L/min, without using a dispersion liquid of nickel hydroxide nanoparticles. This demonstrated that a thin film of cobalt hydroxide could be formed alone.

In condition 2, the flow rates of the carrier gas and flow rate adjustment gas for the nickel hydroxide nanoparticle dispersion were both 1 L/min, the flow rate of the carrier gas for the cobalt hydroxide nanoparticle dispersion was 4 L/min, and the flow rate of the flow rate adjustment gas was 1 L/min. As a result, the Co/Ni mixture ratio in the obtained film was 55%.

In condition 3, the flow rate of the carrier gas for the nickel hydroxide nanoparticle dispersion was 2 L/min, the flow rate of the flow rate adjustment gas was 1 L/min, the flow rate of the carrier gas for the cobalt hydroxide nanoparticle dispersion was 3, and the flow rate of the flow rate adjustment gas was 1 L/min. As a result, the Co/Ni mixture ratio in the obtained film was 26%.

The Co/Ni mixture ratio in the films formed under the above conditions 1 to 3 was measured by energy dispersive X-ray spectrometry (EDX).

(Experiment 6)
(Zn acetylacetonate and nickel hydroxide mixed film)
In the manufacturing method of the nickel hydroxide thin film according to the present embodiment, a solution of Zn acetylacetonate is introduced into the first sprayer of the manufacturing apparatus shown in Fig. 6, a nano-aqueous solution of nickel hydroxide is introduced into the second sprayer, and the mixture is turned into mist and sent to a distributor. A surface SEM photograph of a mixed film of Zn(acac) ₂ and nickel hydroxide formed using the mixed mist is shown in Fig. 8. Fig. 8 also shows the analysis results of O, Ni, Zn, and Si introduced into the mixed film.

In addition, with the same configuration as in Experiment 5, a dispersion of nickel hydroxide nanoparticles can be fed into the first sprayer, and Ni acetylacetonate (Ni(acac) ₂ ), Co acetylacetonate (Co(acac) ₃ ), or cobalt hydroxide can be fed into the second sprayer, and the mixed mist can be used to form a mixed film on a substrate.

(Experiment 7)
An example of the charge/discharge characteristics of a secondary battery having a positive electrode active material layer made of nickel hydroxide formed by the method for producing a nickel hydroxide thin film according to the present embodiment is shown in Fig. 9. In a secondary battery using nickel hydroxide formed by mist spray deposition of nanoparticles by the method for producing a nickel hydroxide thin film according to the present embodiment as a positive electrode active material layer, charge/discharge characteristics equivalent to those obtained when nickel hydroxide was formed by conventional electrical processing of nickel oxide were obtained.

[Secondary battery]
Hereinafter, a secondary battery including a positive electrode active material layer 22 containing nickel hydroxide (Ni(OH) ₂ ) as a positive electrode active material formed by applying the nickel hydroxide thin film manufacturing method according to the present embodiment will be described.

[First embodiment]
As shown in FIG. 10 , the secondary battery 30 according to the first embodiment includes a first electrode (E1) (negative electrode current collector) 12/n-type semiconductor layer 14/negative electrode active material layer (negative electrode) 16/solid electrolyte layer 18/positive electrode active material layer (positive electrode) 22/second electrode (E2) (positive electrode current collector) 26.

As shown in FIG. 12 , the secondary battery 30 according to the first embodiment includes a solid electrolyte layer 18 containing tantalum pentoxide (Ta ₂ O ₅ ) having at least one of water (H ₂ O) and a hydroxyl group (-OH) as a solid electrolyte, a positive electrode active material layer 22 disposed on the upper surface of the solid electrolyte layer 18 and containing nickel hydroxide (Ni(OH) ₂ ) as a positive electrode active material, a second electrode (cathode current collector) 26 disposed on the upper surface of the positive electrode active material layer 22, a negative electrode active material layer 16 disposed on the lower surface of the solid electrolyte layer 18 facing the positive electrode active material layer 22 and containing titanium oxide (TiO _x ) having at least one of water (H ₂ O) and a hydroxyl group (-OH) as a negative electrode active material, and a first electrode (negative electrode current collector) 12 disposed on the lower surface of the negative electrode active material layer 16 facing the second electrode (cathode current collector) 26.

In order to improve the interface state between the positive electrode active material layer 22 and the solid electrolyte layer 18 and facilitate the transfer of electric charges, a _SiO2 -based buffer layer 19 (see FIG. 12, etc.) may be inserted between the positive electrode active material layer 22 and the solid electrolyte layer 18. By inserting a thin SiOx-based film between the solid electrolyte layer ₁₈ ( _Ta2O5 ) and the positive electrode active material layer 22 (Ni(OH) ₂ ), the internal resistance of the battery is reduced.

The positive electrode active material layer 22 can be formed by directly depositing nickel hydroxide (Ni(OH) ₂ ). Note that, as the positive electrode active material of the positive electrode active material layer 22, a nickel hydroxide formed from the nickel oxide by depositing a nickel oxide (NiO) positive electrode active material layer and then subjecting it to electrical processing, for example, repeated charging and discharging, may also be used. Note that, as the positive electrode active material layer 22, nickel oxide (NiO), metallic nickel (Ni), cobalt hydroxide (Co(OH) ₂ ), etc. may also be used.

The positive electrode active material layer 22 has at least nickel hydroxide (Ni(OH) ₂ ) and has a structure that allows the movement of at least one of protons, hydroxide ions ( ^OH- ), and hydronium ions ( _H3O ⁺ ). The valence of nickel atoms in the positive electrode active material layer changes during charging and discharging.

The negative electrode active material layer 16 comprises a titanium oxide compound (TiO _x H _y ) having at least one of water (H ₂ O) and a hydroxyl group (—OH), or titanium oxide (TiO _x ) and silicon oxide (SiO _x ), and allows the movement of at least one of protons, hydroxide ions (OH ⁻ ), and hydronium ions (H ₃ O ⁺ ). The valence of titanium atoms in the negative electrode active material layer changes during charging and discharging.

The above titanium oxide compound may also be formed by applying and baking fatty acid titanium.

The titanium oxide compound may contain a mixture of trivalent and tetravalent titanium atoms, and may further contain water ( _H2O ) or hydroxyl groups (-OH) around the titanium atoms. The titanium oxide compound may have an amorphous structure or a microcrystalline structure.

By optimizing the film thickness and the amount of metal oxide added to the solid electrolyte layer 18, it is possible to form a high resistance layer or an insulating layer against electrons while maintaining the movement of ions. At least one of tantalum oxide (Ta ₂ O ₅ ) and zirconium dioxide (ZrO ₂ ) can be used as the material for the solid electrolyte layer 18.

The n-type semiconductor layer 14 is titanium(IV) oxide having at least one of a rutile type and anatase type crystal structure. The n-type semiconductor layer 14 desirably has at least one of a rutile type crystal structure and an anatase type crystal structure, and has a metal oxide semiconductor with little water (H ₂ O) or hydroxyl groups (-OH). The second electrode (positive electrode current collector) may include any of Al, Ti, ITO, and Ni. The first electrode (negative electrode current collector) may include any of W, Ti, and ITO.

(Examples of configurations of negative electrode active material layer, solid electrolyte layer, and positive electrode active material layer)
11 to 16 show schematic cross-sectional structures of the negative electrode active material layer 16, the solid electrolyte layer 18, and the positive electrode active material layer 22 in the schematic cross-sectional structure of the secondary battery 30 shown in FIG.

The secondary battery 30 illustrated in FIG. 11( a) includes a solid electrolyte layer ₁₈ containing _Ta2O5 as a solid electrolyte, a positive electrode active material layer 22 disposed on the upper surface of the solid electrolyte layer 18 and containing Ni(OH) ₂ as a positive electrode active material, and a negative electrode active material layer 16 disposed on the lower surface of the solid electrolyte layer 18 opposite to the positive electrode active material layer 22 and containing _TiOx as a negative electrode active material.

A secondary battery 30 illustrated in FIG. 11( b) includes a solid electrolyte layer ₁₈ containing _Ta2O5 as a solid electrolyte, a positive electrode active material layer 22 disposed on the upper surface of the solid electrolyte layer 18 and containing Ni(OH) ₂ as a positive electrode active material, and a negative electrode active material layer 16S disposed on the lower surface of the solid electrolyte layer 18 opposite to the positive electrode active material layer 22 and containing _TiOx and _SiOx as negative electrode active materials.

12 to 14 show examples in which a buffer layer 19 for improving the interface is inserted between the positive electrode active material layer 22 and the solid electrolyte layer 18, or a buffer layer 17 for improving the interface is inserted between the negative electrode active material layer 16 and the solid electrolyte layer 18. The buffer layers 17 and 19 are formed, for example, containing silicon oxide (SiO _x ).

Figure 12(a) shows an example of the secondary battery 30 shown in Figure 11(a) in which a buffer layer 19 for improving the interface is inserted between the positive electrode active material layer 22 and the solid electrolyte layer 18, and Figure 12(b) shows an example of the secondary battery 30 shown in Figure 11(b) in which a buffer layer 19 for improving the interface is inserted between the positive electrode active material layer 22 and the solid electrolyte layer 18.

Figure 13(a) shows an example of the secondary battery 30 shown in Figure 12(a) in which a buffer layer 17 for improving the interface is also inserted between the negative electrode active material layer 16 and the solid electrolyte layer 18, and Figure 13(b) shows an example of the secondary battery 30 shown in Figure 12(b) in which a buffer layer 17 for improving the interface is also inserted between the negative electrode active material layer 16S and the solid electrolyte layer 18.

Figure 14(a) shows an example of the secondary battery 30 shown in Figure 11(a) in which a buffer layer 17 for improving the interface is inserted between the negative electrode active material layer 16 and the solid electrolyte layer 18, and Figure 14(b) shows an example of the secondary battery 30 shown in Figure 11(b) in which a buffer layer 17 for improving the interface is inserted between the negative electrode active material layer 16S and the solid electrolyte layer 18.

15 shows an example in which a buffer layer (metal oxide-containing buffer layer) 19MO containing a metal oxide for improving the interface is inserted between the positive electrode active material layer 22 and the solid electrolyte layer 18, or a buffer layer (metal oxide-containing buffer layer) 17MO containing a metal oxide for improving the interface is inserted between the negative electrode active material layer 16 and the solid electrolyte layer 18. The (metal oxide-containing buffer layer) 17MO and 19MO are configured to include silicon oxide (SiO _x ) containing a metal oxide. As the metal oxide contained in the (metal oxide-containing buffer layer) 17MO and 19MO, tin oxide (SnO), alumina (Al ₂ O ₃ ), zirconia (ZrO ₂ ), magnesium oxide (MgO), phosphorus oxide (P _x O _y ), etc. can be applied.

Fig. 15(a) shows an example in which a metal oxide-containing buffer layer 19MO for improving an interface is inserted between the positive electrode active material layer 22 and the solid electrolyte layer 18 in the secondary battery 30 shown in Fig. 11(b), and Fig. 15(b) shows an example in which a metal oxide-containing buffer layer 17MO for improving an interface is inserted between the negative electrode active material layer 16S and the solid electrolyte layer 18 in the secondary battery 30 shown in Fig. 11(b). Note that the negative electrode active material layer 16S (TiO _x +SiO _x ) in Figs. 15(a) and 15(b) may each be replaced with the negative electrode active material layer 16 (TiO _x ).

FIG. 16 also shows an example of a positive electrode active material layer 22S containing SiO _x (a buffer layer material) therein, and an example of a negative electrode active material layer 16S containing SiO _x (a buffer layer material) therein.

The secondary battery 30 illustrated in FIG. 16( a) includes a solid electrolyte layer ₁₈ containing _Ta2O5 as a solid electrolyte, a positive electrode active material layer 22S disposed on the upper surface of the solid electrolyte layer 18 and containing Ni(OH) ₂ as a positive electrode active material and _SiOx as a buffer layer material, and a negative electrode active material layer 16 disposed on the lower surface of the solid electrolyte layer 18 opposite to the positive electrode active material layer 22S and containing _TiOx as a negative electrode active material.

The secondary battery 30 illustrated in FIG. 16( b) includes a solid electrolyte layer ₁₈ containing _Ta2O5 as a solid electrolyte, a positive electrode active material layer 22S disposed on the upper surface of the solid electrolyte layer 18 and containing Ni(OH) ₂ as a positive electrode active material and _SiOx as a buffer layer material, and a negative electrode active material layer 16S disposed on the lower surface of the solid electrolyte layer 18 opposite to the positive electrode active material layer 22S and containing _TiOx as a negative electrode active material and _SiOx as a buffer layer material.

The secondary battery 30 according to the embodiment illustrated in Figures 12 to 16 can improve the exchange of charges between the positive electrode active material layer 22 and the solid electrolyte layer 18, or between the negative electrode active material layer 16 and the solid electrolyte layer 18, thereby improving the electricity storage performance.

[Second embodiment]
As shown in FIG. 17 , the secondary battery 30 according to the second embodiment has a configuration of a first electrode (E1) (negative electrode) 12/negative electrode active material layer 16/solid electrolyte layer 18/positive electrode active material layer 22/p-type semiconductor layer 24/second electrode (E2) (positive electrode current collector) 26.

The secondary battery 30 according to the second embodiment has a structure in which a p-type semiconductor layer 24 is inserted on the positive electrode active material layer 22.

As shown in FIG. 18, the secondary battery 30 according to the second embodiment includes a p-type semiconductor layer 24 disposed between the positive electrode active material layer and the second electrode (positive electrode current collector).

The p-type semiconductor layer 24 functions as a charge transport layer and may comprise, for example, nickel oxide (NiO) having a crystalline structure. The other configurations are the same as those of the first embodiment.

[Third embodiment]
18, a secondary battery 30 according to the third embodiment includes a first electrode (E1) (negative electrode current collector) 12/n-type semiconductor layer 14/negative electrode active material layer 16T/solid electrolyte layer 18/cathode active material layer 22/p-type semiconductor layer 24/second electrode (E2) (cathode current collector) 26. The difference from the second embodiment is that the negative electrode active material layer 16T contains a titanium oxide compound (TiO _x ) and does not contain silicon oxide.

The p-type semiconductor layer 24 functions as a conductive hole transport layer and may have, for example, nickel oxide (NiO). The other configurations are the same as those of the second embodiment. The secondary battery 30 according to the embodiment illustrated in Figures 13 to 18 can also be applied to the second and third embodiments, as in the first embodiment. In addition, the application of a high ion conductive film makes it possible to control and optimize the film thickness, which is expected to improve cycle characteristics and manufacturing stability.

[Other embodiments]
As described above, although several embodiments have been described, the descriptions and drawings forming a part of the disclosure are illustrative and should not be understood as limiting. From this disclosure, various alternative embodiments, examples and operating techniques will become apparent to those skilled in the art.

As such, this embodiment includes various embodiments not described here.

The secondary battery of this embodiment can be used in a variety of consumer and industrial devices, and can be used in a wide range of fields, such as secondary batteries for communication terminals and wireless sensor networks, and secondary batteries for system applications that can transmit various sensor information with low power consumption.

12...First electrode (E1) (negative electrode)
14...n-type semiconductor layer ( _TiO2 )
16...Negative electrode active material layer (TiO _x )
16S: negative electrode active material layer (TiO _x and SiO _x )
16T...Negative electrode active material layer (TiO _x )
17...Buffer layer (SiO _x )
17MO...metal oxide-containing buffer layer (SiO _x containing metal oxide)
18...Solid _electrolyte layer ( _Ta2O5 )
18SS...Solid electrolyte layer (SiO _x + SnO)
19...Buffer layer (SiO _x )
19MO...metal oxide-containing buffer layer (SiO _x containing metal oxide)
22... Positive electrode active material layer (Ni(OH) ₂ )
22S: Positive electrode active material layer (Ni(OH) ₂ + _SiOx )
24...p-type semiconductor layer (NiO)
26...Second electrode (E2) (positive electrode)
30... Secondary battery 40... Substrate 80... Classifier 90... Mixing container 110... Film forming device section 120... Nozzle 130... Stage 140... Dispersion liquid 150, 250... Dispersion liquid container 160, 260... Mist generator 240... Metal compound solution 101, 102, 103... Manufacturing device L1, L2, L3... Path M1, M2, M3, M4... Mist G1, G1'... Carrier gas (first inert gas)
G2, G2': flow rate adjusting gas (second inert gas)

Claims (4)

A first step of preparing a dispersion liquid in which nickel hydroxide nanoparticles are dispersed;
a second step of misting the dispersion with ultrasonic waves to produce a nickel hydroxide solution mist containing nickel hydroxide nanoparticles;
a third step of transporting the nickel hydroxide solution mist with an inert gas;
A fourth step of discharging the nickel hydroxide solution mist transported in the third step onto a heated substrate. A step of misting a dispersion liquid in which nickel hydroxide nanoparticles are dispersed in a first container to obtain a nickel hydroxide solution mist;
transporting the nickel hydroxide solution mist through a mist path with a first inert gas;
receiving the nickel hydroxide solution mist in a classifier disposed downstream of the mist path;
discharging the nickel hydroxide solution mist from the classifier onto a heated substrate. A step of misting a dispersion liquid in which nickel hydroxide nanoparticles are dispersed in a first container to obtain a nickel hydroxide solution mist;
A step of obtaining a metal compound mist by misting a metal compound solution containing a metal compound in a second container independent of the first container;
a step of mixing the nickel hydroxide solution mist and the metal compound mist in a mixing vessel receiving the nickel hydroxide solution mist and the metal compound mist via first and second paths independent of each other to obtain a mixed mist;
discharging the mixed mist from the mixing container through a third path onto a heated substrate, and forming a film of nickel hydroxide mixed with a metal oxide on the substrate. The method for producing a nickel hydroxide thin film according to claim 1 , further comprising a step of adjusting the temperature of the substrate .

Images