JP7100170B2 - Secondary battery - Google Patents

Description

The present embodiment relates to a secondary battery.

Since the conventional secondary battery does not use an electrolytic solution / rare element and can be thinned, the first electrode / insulator / n-type oxide semiconductor layer / p-type oxide semiconductor layer / second electrode is used. Stacked secondary batteries have been proposed.

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

Japanese Patent No. 5508542 Japanese Patent No. 5297809 JP-A-2015-82445 Japanese Unexamined Patent Publication No. 2016-82125

The present embodiment provides a highly reliable secondary battery capable of improving the energy density and increasing the battery characteristics (storage capacity).

According to one aspect of the present embodiment, a first conductive type first oxide semiconductor layer and a first insulator and a first conductive type second oxide are arranged on the first oxide semiconductor layer. A first charging layer made of a semiconductor, a second charging layer including a second insulator and a conductivity adjusting material, and a second conductive type third oxide semiconductor layer arranged on the first charging layer. , A metal hydroxide that is arranged between the second charging layer and the third oxide semiconductor layer and constitutes the third oxide semiconductor layer, and is a metal hydroxide and an oxywater by an electric field. The third oxide semiconductor layer is provided with nickel oxide (NiO), and the hydroxide layer is provided with nickel hydroxide (Ni (OH) ₂ ). Alternatively, a secondary battery comprising at least one of nickel oxyhydroxide (NiOOH) is provided.

According to the present embodiment, it is possible to provide a highly reliable secondary battery capable of improving the energy density and increasing the battery characteristics (storage capacity).

Schematic cross-sectional structural view of the secondary battery which concerns on embodiment. (A) Energy band diagram before charging the secondary battery according to the embodiment, (b) Schematic configuration diagram of each layer corresponding to FIG. 2 (a). (A) Energy band diagram during charging (forward bias state) of the secondary battery according to the embodiment, (b) Schematic configuration diagram of each layer corresponding to FIG. 3 (a). (A) Energy band diagram in a fully charged state of the secondary battery according to the embodiment, (b) Schematic configuration diagram of each layer corresponding to FIG. 4 (a). (A) Energy band diagram in the discharged state (connected to the load) of the secondary battery according to the embodiment, (b) Schematic configuration diagram of each layer corresponding to FIG. 5 (a). (A) Energy band diagram in a fully discharged state of the secondary battery according to the embodiment, (b) Schematic configuration diagram of each layer corresponding to FIG. 6 (a). (A) A schematic circuit configuration diagram of a control system applied to an electrical stimulation step of forming a hydroxide layer between a first charging layer and a third oxide semiconductor layer in the secondary battery according to the embodiment. (B) An example of the waveform of the pulse voltage _VA applied between the first electrode and the second electrode. The figure which shows the experimental result of the relationship between the energy density and the electrical stimulation time in the secondary battery which concerns on embodiment. An example of a scanning electron microscope (SEM) photograph of a cross section of a sample in which a second charging layer is made of silicone oil in a secondary battery according to an embodiment. An example of a SIMS profile for each element in the secondary battery according to the embodiment shown in FIG. The figure which shows the relationship between the resistance R (a.u.) and the energy density (a.u.) between the 1st electrode and the 2nd electrode with respect to the addition amount of the conductivity adjusting material in the secondary battery which concerns on embodiment.

Next, the present embodiment will be described with reference to the drawings. In the description of the drawings described below, the same or similar parts are designated by the same or similar reference numerals. However, it should be noted that the drawings are schematic and the relationship between the thickness of each component and the plane dimensions is different from the actual one. Therefore, the specific thickness and dimensions should be determined in consideration of the following explanation. In addition, it goes without saying that parts of the drawings having different dimensional relationships and ratios are included.

Further, the embodiments shown below exemplify devices and methods for embodying the technical idea, and do not specify the material, shape, structure, arrangement, etc. of each component. This embodiment can be modified in various ways within the scope of the claims.

[Embodiment]
The schematic cross-sectional structure of the secondary battery according to the embodiment is shown as shown in FIG. Hereinafter, the secondary battery 30 according to the embodiment will be described.

As shown in FIG. 1, the secondary battery 30 according to the embodiment is arranged on the first conductive type first oxide semiconductor layer 14 and the first oxide semiconductor layer 14, and is the first insulator and the first. A first charging layer 16 composed of a first conductive type second oxide semiconductor, a second conductive type third oxide semiconductor layer 24 arranged on the first charging layer 16, a first charging layer 16 and a first. It is provided between the three oxide semiconductor layer 24 and the hydroxide layer 22 having a metal hydroxide constituting the third oxide semiconductor layer 24.

Further, as shown in FIG. 1, the secondary battery 30 according to the embodiment may include a second charging layer 18 arranged between the first charging layer 16 and the hydroxide layer 22.

Here, the second charging layer 18 may include a second insulating material.

Further, the second charging layer 18 may include a second insulating material and a conductivity adjusting material.

Further, the first charging layer 16 may have a composition different from each other and may have at least a two-layer structure. The first charging layer 16 may be formed of, for example, silicon oxide (SiO ₂ ) / titanium oxide (TiO ₂ ). Specifically, it may be formed by a layered structure of SiO ₂ / TiO ₂ , or may be formed by a particle bonding structure in which the periphery of the particle-shaped TiO ₂ is covered with SiO ₂ . Further, the first charging layer 16 may have a structure in which TIO ₂ is mixed with SiO ₂ or TIO ₂ is wrapped in silicon oxide. Further, in the above, the composition of titanium oxide and silicon oxide is not limited to TiO ₂ and SiO ₂ , and may have a configuration in which the composition ratio x such as TiO _x or SiO _x is changed.

Further, since the n-type oxide semiconductor may be an oxide of titanium (Ti), tin (Sn), zinc (Zn), magnesium (Mg), SiO ₂ and Ti, Sn, Zn, Mg can be used. It may have a layered structure of an oxide, or may be formed by a particle bonding structure in which the periphery of a particle-shaped oxide of Ti, Sn, Zn, or Mg is coated with SiO ₂ . Further, it may have a structure in which molecules or molecular groups of SiO ₂ and oxides of Ti, Sn, Zn, and Mg are surrounded by SiO ₂ (amorphous).

Further, the first charging layer 16 may have a porous structure.

Further, the second oxide semiconductor may include at least one oxide selected from the group consisting of oxides of Ti, Sn, Zn, or Mg.

Further, the conductivity adjusting material may include a first conductive type semiconductor or an oxide of a metal.

Further, the conductivity adjusting material may include at least one oxide selected from the group consisting of oxides of Sn, Zn, Ti, or niobium (Nb).

Specifically, in the secondary battery 30 according to the embodiment, the second insulator may be provided with SiO ₂ , and the conductivity adjusting material may be provided with SnO _x .

Further, in the secondary battery 30 according to the embodiment, the second insulator may include SiO _x formed from silicone oil.

Further, in the secondary battery 30 according to the embodiment, the first insulator may be provided with SiO ₂ and the second oxide semiconductor may be provided with TiO ₂ .

(Hydroxide layer)
When the hydroxide layer 22 is charged, the metal hydroxide is reduced by applying an electric field to convert holes (h ⁺ ) into hydrogen ions (H ⁺ ), and when discharged, the hydrogen ions are converted into holes. It is a layer to be converted into.

When the hydroxide is nickel hydroxide, the reaction formula is as follows.

-Nickel hydroxide layer-
Nickel hydroxide (Ni (OH) ₂ ) is changed to nickel oxyhydroxide (NiOOH) by applying an electric field. During charging, the reaction of Ni (OH) ₂ + h ⁺ → NiOOH + H ⁺ proceeds, and during discharging, the reaction of NiOOH + H ⁺ → Ni (OH) ₂ + h ⁺ proceeds. This reaction involves electrochromism.

(1st charging layer)
The first charging layer 16 is a layer that is paired with the hydroxide layer 22 and accumulates hydrogen generated during charging. In the first charging layer 16, the reaction of M + H ₂ O + e-→ MH + OH ^- progresses during charging ^{, and the reaction of MH + OH-→ M + H 2 O + e- progresses} _during ^discharging . By making it porous, the efficiency of hydrogen accumulation can be increased. In addition, hydrogen storage and conductivity can be optimized by using a plurality of layers. It can be optimized by using the second oxide semiconductor as an oxide of Ti, Sn, Zn or Mg.

(Second charging layer)
The second charging layer 18 is a buffer layer for adjusting the movement of H ⁺ and electrons (e ⁻ ). By adding a conductivity adjusting material, the mobility of H ⁺ and e ^- can be further adjusted. By using an oxide of Sn, Zn, Ti or Nb as the conductivity adjusting material, the second charging layer 18 can be formed thick and electrically with high withstand voltage.

(P-type oxide semiconductor layer)
The oxide semiconductor layer 24 forms a pn junction with the n-type semiconductor of the hydroxide layer (NiOOH of the nickel hydroxide layer), and can suppress charge leakage during charging. By using NiO for the p-type oxide semiconductor layer 24, it is possible to form _two Ni (OH) layers by electrical stimulation.

(N-type first oxide semiconductor layer)
The n-type first oxide semiconductor layer 14 has an electric resistance between the first electrode 12 and the first charging layer 16 and facilitates electrical bonding.

As shown in FIG. 1, the secondary battery 30 according to the embodiment includes a first electrode 12 and a second electrode 26, and the first oxide semiconductor layer 14 includes an n-type first oxide semiconductor layer. The second oxide semiconductor is provided with an n-type second oxide semiconductor, the third oxide semiconductor layer 24 is provided with a p-type third oxide semiconductor layer, and the second electrode 26 is connected to the first electrode 12. It may be connected to.

More specifically, in the secondary battery 30 according to the embodiment, the third oxide semiconductor layer 24 is provided with nickel oxide (NiO), and the hydroxide layer 22 is made of nickel hydroxide (Ni (OH) ₂ ) or It may be provided with at least one of nickel oxyhydroxide (NiOOH).

Further, in the secondary battery 30 according to the embodiment, the third oxide semiconductor layer 24 is provided with nickel oxide (NiO), and the hydroxide layer 22 is nickel hydroxide (Ni (OH) ₂ ) and nickel oxyhydroxide. It has a laminated structure in which both (NiOOH) are mixed, and nickel hydroxide (Ni (OH) ₂ ) is in contact with the third oxide semiconductor layer 24, and nickel oxyhydroxide (NiOOH) is in contact with the second charging layer 18. You may have.

Further, in the secondary battery 30 according to the embodiment, the third oxide semiconductor layer 24 is provided with nickel oxide (NiO), and the hydroxide layer 22 is provided with nickel oxyhydroxide (NiOOH) when fully charged. At the time of full discharge, nickel hydroxide (Ni (OH) ₂ ) is provided.

Further, nickel hydroxide (Ni (OH) ₂ ) changes to nickel oxyhydroxide (NiOOH) during charging when the second electrode 26 is positively biased with respect to the first electrode 12.

Further, nickel oxyhydroxide (NiOOH) changes to nickel hydroxide (Ni (OH) ₂ ) at the time of discharge via a load connected between the first electrode 12 and the second electrode 26.

The hydroxide layer 22 may be formed directly on the second charging layer 18, or, as will be described later, the p-type third oxide semiconductor layer 24 and the n-type first oxide semiconductor layer 14 A pulse voltage may be periodically applied between the two to form.

In the secondary battery 30 according to the embodiment, a nickel hydroxide (Ni (OH) ₂ ) layer is formed between the charging layer (first charging layer 16 + second charging layer 18) 20 and the third oxide semiconductor layer 24. The storage capacity can be increased by forming the above.

Further, in the secondary battery 30 according to the embodiment, a layer (Ni (OH) _X ), Si (Ni (OH) X) containing a large amount of OH groups between the second charging layer 18 and the p-type third oxide semiconductor layer 24. OH) A configuration in which _X is formed and inserted may be adopted. By providing such a configuration, the storage capacity can be increased and the battery performance can be improved. That is, the hydroxide layer 22 is not limited to nickel hydroxide (Ni (OH) ₂ ), but is a mixture of layers containing a large amount of OH groups (Ni (OH) _x ), Si (OH) _x , and the like. It may be formed as a layer. Further, structurally, Ni, Si, O, H, and a compound of an element constituting the second charging layer 18 may be contained.

(Energy band diagram)
In the following, the p-type third oxide semiconductor layer 24 is nickel oxide (NiO), and the hydroxide layer 22 is at least one of nickel hydroxide (Ni (OH) ₂ ) or nickel oxyhydroxide (NiOOH), the first. An example will be described in which the charging layer 16 is formed of SiO ₂ / TiO ₂ and the second charging layer 18 is formed of SiO ₂ / SnO.

-Before charging-
The energy band diagram of the secondary battery 30 before charging according to the embodiment is shown as shown in FIG. 2 (a), and the schematic configuration of each layer corresponding to FIG. 2 (a) is shown in FIG. 2 (b). It is expressed as shown in. Here, E _f represents the Fermi level.

The p-type third oxide semiconductor layer 24 of nickel oxide (NiO) is connected to the second electrode (26) E2, and the first charging layer 16 of SiO ₂ / TiO ₂ is connected to the first electrode (12) E1. There is.

In the thermal equilibrium state, the energy band diagram of the secondary battery 30 according to the embodiment before charging is shown as shown in FIG. 2 (a), and NiO / Ni (OH) ₂ with respect to the vacuum level. The conduction band of / SnO / TiO ₂ exists at the level of 1.8 eV / 1.47 eV / 4.3 to 4.5 eV / 4.3 eV. The bandgap energy E _g of NiO / Ni (OH) ₂ / SnO / TiO ₂ is 4.0 eV / 3.7 eV / 3.8 eV / 3.2 eV. The bandgap energy E _g of SiO ₂ constituting the charging layer 20 is 8.9 eV. Before charging, the hydroxide layer 22 is nickel hydroxide (Ni (OH) ₂ ).

-Charging (forward bias state)-
The energy band diagram of the secondary battery 30 according to the embodiment during charging (forward bias state) is shown as shown in FIG. 3 (a), and the schematic configuration of each layer corresponding to FIG. 3 (a) is shown. It is represented as shown in FIG. 3 (b).

An energy band diagram in a state where the second electrode E2 is connected to a plus (+) and the first electrode E1 is connected to a minus (-) and a charging voltage of, for example, about 2.8 V is applied is shown in FIG. 3 (a). It is expressed as. Here, the Fermi level E _f in a state where about 2.8 V is applied is represented as shown in FIG. 3 (a).

In the secondary battery 30 according to the embodiment, the hydroxide layer 22C being charged produces nickel oxyhydroxide (NiOOH) from nickel hydroxide (Ni (OH) ₂ ), so that the hydroxide being charged As shown in FIGS. 3A and 3B, the layer 22C is represented by a layer structure of nickel hydroxide (Ni (OH) ₂ ) / nickel oxyhydroxide (NiOOH). The nickel hydroxide (Ni (OH) ₂ ) layer is mainly arranged on the nickel oxide layer (NiO) side, and the nickel oxyhydroxide (NiOOH) layer is arranged on the second charging layer 18 side.

During charging, about 2.8 V is applied as a positive voltage between the second electrode E2 and the first electrode E1, so that inside the secondary battery 30, electrons e ⁻ from the first electrode E1 are n in the charging layer 20. It is injected into the type oxide semiconductor (TiO ₂ ), and the hole h ⁺ is injected into the p-type oxide semiconductor layer (NiO) 24 from the second electrode E2.

With the assistance of water or water vapor component (H ₂ O) ^, the reaction of Ni (OH) ₂ + OH- → NiOOH + H ₂ O + e ^- progresses on the positive electrode side ^, while the reaction of M + H ₂ O + e- → MH + OH ^- on the negative electrode side. Progresses. Here, M represents a metal element in the charging layer 20.

As a result, in the hydroxide layer 22C being charged, the reaction of Ni (OH) ₂ + h ⁺ → NiOOH + H ⁺ proceeds, so the synthesis of hydrogen ion H ⁺ and electron e ^- as shown in FIG. 3 (a). In addition, hydrogen accumulation is realized in the charging layer 20 with the assistance of water or a water vapor component (H ₂ O). Here, in hydrogen storage, hydrogen H is bonded to the dangling bonds of Ti and Si in the charging layer 20. It is also possible to bond in the form of OH.

-Full charge-
The energy band diagram of the secondary battery 30 according to the embodiment in a fully charged state is represented as shown in FIG. 4 (a), and the schematic configuration of each layer corresponding to FIG. 4 (a) is shown in FIG. 4 (b). ). The conduction band of NiO / NiOOH exists at the level of 1.8 eV + 2.8 eV / ΔeV + 2.8 eV with respect to the vacuum level. The bandgap energy E _g of NiOOH is 1.75 eV.

In the open state after full charge in which hydrogen is fully accumulated in the charging layer 20, a holding voltage slightly lower than that at the time of charging (2.8 V) is held between the second electrode E2 and the first electrode E1.

Further, in the fully charged state of the secondary battery 30 according to the embodiment, the nickel hydroxide (Ni (OH) ₂ ) layer 22 changes to the nickel hydroxide (NiOOH) layer 22F, which is unstable NiOOH. Energy is stored as a chemical potential.

-Discharging-
The energy band diagram in the discharged state (connected to the load) of the secondary battery 30 according to the embodiment is shown as shown in FIG. 5A, and the schematic configuration of each layer corresponding to FIG. 5A is , As shown in FIG. 5 (b). That is, the energy band diagram in the discharged state (connected to the load) in which the load 42 is connected between the second electrode E2 and the first electrode E1 is shown as shown in FIG. 5A. Here, the Fermi level E _f in a state where about 2.8 V is applied gradually increases according to the discharge state, as shown in FIG. 5 (a). In the discharged state (connected to the load) of the secondary battery 30 according to the embodiment, the reverse reaction of the above charging operation occurs.

In the secondary battery 30 according to the embodiment, the hydroxide layer 22D during discharge produces nickel hydroxide (Ni (OH) ₂ ) from nickel oxyhydroxide (NiOOH), so that the hydroxide during discharge is generated. As shown in FIGS. 5 (a) and 5 (b), the layer 22D is represented by a layer structure of nickel hydroxide (Ni (OH) ₂ ) / nickel oxyhydroxide (NiOOH). The nickel hydroxide (Ni (OH) ₂ ) layer is mainly formed on the nickel oxide layer (NiO) side, and the nickel oxyhydroxide (NiOOH) layer is formed on the second charging layer 18 side.

During the discharge, the load 42 is externally connected between the second electrode E2 and the first electrode E1, so that inside the secondary battery 30, electrons e ⁻ are emitted from the n-type oxide semiconductor (TiO ₂ ) of the charging layer 20. It is emitted to the first electrode E1 and hole h ⁺ is emitted from the p-type oxide semiconductor layer (NiO) 24 to the second electrode E2.

With the assistance of water or water vapor component (H ₂ O), the reaction of NiOOH + H ₂ O + e- → Ni (OH ⁾ ₂ + OH ^- progresses on the positive electrode side ^, while the reaction of MH + OH- → M + H ₂ O + e ^- on the negative electrode side. Progresses.

As a result, in the hydroxide layer 22D being discharged, the reaction of NiOOH + H ⁺ → Ni (OH) ₂ + h ⁺ proceeds. Therefore, as shown in FIG. 5A, hydrogen ion H ⁺ in the charging layer 20. The separation of the electron e ^- and the hydrogen storage state is realized by the assist of water or water vapor component (H ₂ O).

-Full discharge state-
The energy band diagram of the secondary battery 30 according to the embodiment in a fully discharged state is shown as shown in FIG. 6 (a), and the schematic configuration of each layer corresponding to FIG. 6 (a) is shown in FIG. 6 (b). ).

In the fully discharged state, nickel oxyhydroxide (NiOOH) is transformed into the nickel hydroxide (Ni (OH) ₂ ) layer 22.

In the fully discharged state, the energy band diagram of the secondary battery 30 according to the embodiment is represented as shown in FIG. 6A, with respect to the vacuum level, NiO / Ni (OH) ₂ / SnO /. The conduction band of TiO ₂ exists at the level of 1.8 eV / 1.47 eV / 4.3 to 4.5 eV / 4.3 eV. The bandgap energy E _g of NiO / Ni (OH) ₂ / SnO / TiO ₂ is 4.0 eV / 3.7 eV / 3.8 eV / 3.2 eV. The bandgap energy E _g of SiO ₂ constituting the charging layer 20 is 8.9 eV. In the fully discharged state, the hydroxide layer 22 is nickel hydroxide (Ni (OH) ₂ ).

In the fully discharged state, the state is restored to the same state as the thermal equilibrium state before charging.

(Production method)
The method for manufacturing the secondary battery 30 according to the embodiment includes a step of forming the first conductive type first oxide semiconductor layer 14 and a first insulator and a first conductive material on the first oxide semiconductor layer 14. A step of forming a first charge layer 16 made of a second oxide semiconductor of a mold, a step of forming a second charge layer 18 on the first charge layer 16, and a second conductive type on the second charge layer 18. Water having a metal hydroxide constituting the third oxide semiconductor layer 24 between the step of forming the third oxide semiconductor layer 24 and the first charging layer 16 and the third oxide semiconductor layer 24. It has a step of forming an oxide layer 22.

―N-type oxide semiconductor layer 14―
A TiO ₂ film is formed on the first electrode 12 constituting the lower electrode, for example, by forming a film by a spatter deposition method. Here, Ti or TiO can be used as a target. The film thickness of the n-type oxide semiconductor layer 14 is, for example, about 50 nm-200 nm. For the first electrode 12, for example, a tungsten (W) electrode or the like can be applied.

―First charging layer 16―
The chemical solution is formed by stirring fatty acid titanium and silicone oil together with a solvent. This chemical solution is applied onto the n-type oxide semiconductor layer 14 using a spin coating device. The rotation speed is, for example, about 500-3000 rpm. After application, dry on a hot plate. The drying temperature on the hot plate is, for example, about 30 ° C. to 200 ° C., and the drying time is, for example, about 5 minutes to 30 minutes. Bake after drying. For firing after drying, a firing furnace is used and firing is performed in the atmosphere. The firing temperature is, for example, about 300 ° C. to 600 ° C., and the firing time is, for example, about 10 minutes to 60 minutes.

As a result, the aliphatic salt is decomposed to form a fine particle layer of titanium dioxide covered with a silicone insulating film. The above-mentioned manufacturing (manufacturing) method in which titanium dioxide covered with a silicone insulating film is layered is a coating pyrolysis method. Specifically, this layer has a structure in which a metal salt of titanium dioxide coated with silicone is embedded in the silicone layer. After firing, UV irradiation with a low-pressure mercury lamp is carried out. The UV irradiation time is, for example, about 10 to 100 minutes.

-Second charging layer (buffer layer) 18 (method 1)-
The chemical solution is formed by stirring fatty acid tin and silicone oil together with a solvent. This chemical solution is applied onto the first charging layer 16 using a spin coating device. The rotation speed is, for example, about 500-3000 rpm. After application, dry on a hot plate. The drying temperature on the hot plate is, for example, about 30 ° C. to 200 ° C., and the drying time is, for example, about 5 minutes to 30 minutes. Further, it is dried and then fired. For firing after drying, a firing furnace is used and firing is performed in the atmosphere. The firing temperature is, for example, about 300 ° C. to 600 ° C., and the firing time is, for example, about 10 minutes to 60 minutes. After firing, UV irradiation with a low-pressure mercury lamp is carried out. The UV irradiation time is, for example, about 10 to 100 minutes. The film thickness of the second charging layer (buffer layer) 18 after UV irradiation is, for example, about 100 nm-300 nm.

-Second charging layer (buffer layer) 18 (method 2)-
The chemical solution is formed by stirring silicone oil together with a solvent. This chemical solution is applied onto the first charging layer 16 using a spin coating device. The rotation speed is, for example, about 500-3000 rpm. After application, dry on a hot plate. The drying temperature on the hot plate is, for example, about 50 ° C. to 200 ° C., and the drying time is, for example, about 5 minutes to 30 minutes. Further, it is dried and then fired. For firing after drying, a firing furnace is used and firing is performed in the atmosphere. The firing temperature is, for example, about 300 ° C. to 600 ° C., and the firing time is, for example, about 10 minutes to 60 minutes. After firing, UV irradiation with a low-pressure mercury lamp is carried out. The UV irradiation time is, for example, about 10 to 60 minutes. The film thickness of the second charging layer (buffer layer) 18 after UV irradiation is, for example, about 10 nm-100 nm.

―P-type third oxide semiconductor layer 24-
A NiO film is formed on the second charging layer 18 by, for example, forming a film by a spatter deposition method. Here, Ni or NiO can be used as a target. The film thickness of the p-type oxide semiconductor layer 24 is, for example, about 200 nm to 1000 nm.

―Second electrode 26―
The second electrode 26 as the upper electrode is formed, for example, by forming Al into a film by a sputtering deposition method or a vacuum vapor deposition method. A film can be formed on the p-type third oxide semiconductor layer (NiO) 24 using an Al target. For the second electrode 26, for example, a stainless steel mask may be used to form a film only in a designated area.

―Ni (OH) _2―
It is formed by using an electrical stimulation step in which an electrical treatment is performed after the formation of the second electrode 26.

The first electrode 12 is set as the ground potential, and positive and negative voltages are alternately applied to the second electrode 26. The atmosphere is the atmosphere, and the humidity is, for example, about 20% -60%.

In the secondary battery 30 according to the embodiment, the schematic circuit configuration of the control system applied to the electrical stimulation step of forming the hydroxide layer between the charging layer 20 and the third oxide semiconductor layer 24 is shown in FIG. 7. An example of the waveform of the pulse voltage _VA applied between the first electrode 12 and the second electrode 26 is shown as shown in FIG. 7 (b). In FIG. 7A, the connection relationship of the circuit is represented by a thick line, and the signal flow is represented by a thin line.

As shown in FIG. 7A, the pulse voltage _VA applied to the second electrode 26 of the secondary battery 30 to which the first electrode 12 is grounded is a voltage via the ammeter 34, the voltmeter 36, and the resistor 38. It is supplied from the source 32. The voltage source 32 can be controlled by the control device 40. Further, since the values of the ammeter 34 and the voltmeter 36 are fed back to the control device 40, the pulse voltage _VA shown in FIG. 7B can be supplied by the voltage source 32 controlled by the control device 40. ..

As shown in FIG. 7B, the pulse voltage _VA is, for example, 3V (5 seconds) → -3V (2 seconds) → 5V (0.5 seconds) → −0.4V (4.5 seconds). By applying about 300 cycles to 5000 cycles as the period TC, the Ni (OH) ₂ layer 22 can be formed between the second charging layer 18 and the third oxide semiconductor layer (NiO) 24. It should be noted that the presence of substances containing Si, O, H, and Ni in the Ni (OH) ₂ layer 22 has been detected from the measurement results of the secondary ion mass spectrometry (SIMS). ..

Even in a structure in which only the first charging layer 16 is provided as the charging layer 20 and the second charging layer 18 is not provided, the charging layer 20 is between the first charging layer 16 and the third oxide semiconductor layer 24 by the above electrical stimulation step. A hydroxide layer can be formed.

The pulse voltage waveform shown in FIG. 7B is an example, and the voltage, the number of pulses per cycle, the order of positive and negative voltages, and the like can be appropriately selected depending on the configuration of the secondary battery 30. It is also possible to select a pulse waveform without applying a negative voltage.

(Relationship between energy density and electrical stimulation time)
In the secondary battery 30 according to the embodiment, the experimental result of the relationship between the energy density and the electrical stimulation time is shown as shown in FIG. Here, the electrical stimulation time corresponds to the time when a pulse voltage _VA of 1 cycle TC = 12 seconds is applied for a plurality of cycles.

As shown in FIG. 8, the energy density tends to increase as the electrical stimulation time increases. It has been confirmed that the film thickness of the hydroxide (Ni (OH) _x ) layer 22 increases with the passage of the electrical stimulation time.

In the embodiment, the nickel hydroxide (Ni (OH) ₂ ) layer 22 is formed between the charging layer 20 and the third oxide semiconductor layer (NiO) 24, whereby Ni (OH) is used during charging. Since the reaction of ₂ + h ⁺ → NiOOH + H ⁺ proceeds and the reaction of NiOOH + H ⁺ → Ni (OH) ₂ + h ⁺ proceeds during discharge, it is possible to provide the secondary battery 30 with an increased storage capacity.

(Experimental result)
In the secondary battery 30 according to the embodiment, an example of a cross-sectional SEM photograph of a sample obtained by producing a second charging layer 18 using only silicone oil and undergoing an electrical stimulation step is shown as shown in FIG.

Apparently, a hydroxide (Ni (OH) ₂ ) layer 22 is formed between the second charging layer (buffer layer) 18 and the third oxide semiconductor layer (NiO) 24 formed only of silicone oil. There is.

(SIMS analysis)
In the secondary battery 30 according to the embodiment shown in FIG. 9, mass spectrometry of each element was performed while digging from the surface of the third oxide semiconductor layer (NiO) 24, and a SIMS profile for each element was obtained. ..

In the sample not subjected to the electrical stimulation step (curve WO in FIG. 10), the region with the Si peak near the depth 5 (a.u.) corresponds to the second charging layer (buffer layer) 18 using only silicone oil. do. A peak of H is observed at the interface between the buffer layer 18 and the third oxide semiconductor layer (NiO) 24 (the portion where the depth is the vertical line A).

On the other hand, in the sample (curve W in FIG. 10) that has undergone the electrical stimulation step, there is a region having a large amount of H in the portion where the depth is on the left side of the vertical line A, and the hydroxide (Ni (OH) ₂ ) layer 22 has a region. Presumed to be due to existence.

The hydroxide (Ni (OH) ₂ ) layer 22 is electrochemically formed by an electrical stimulation step. Therefore, the presence of Si can be confirmed in the SIMS profile (curve W in FIG. 10) due to the introduction of Si from SiO _x of the underlying second charging layer (buffer layer) 18.

In the secondary battery 30 according to the embodiment, the relationship between the resistance R (a.u.) and the energy density (a.u.) between the first electrode and the second electrode with respect to the amount of the conductivity adjusting material added is shown as shown in FIG. To. The energy density (a.u.) corresponds to the discharge capacity of the secondary battery 30.

In FIG. 11, the conductivity adjusting material addition amount corresponds to a value related to the addition amount of SnO _x in the second charging layer (buffer layer) 18. As shown in FIG. 11, the values of the resistance R (au) and the energy density (au) between the first electrode and the second electrode are optimum with respect to the values related to the amount of SnO _x added in the second charging layer 18. There is a value.

In the secondary battery 30 according to the embodiment, the second charging layer (buffer layer) 18 is composed of an insulator and a conductivity adjusting material, and the amount of the conductivity adjusting material added can be controlled to optimize the energy density. Is.

(Laminate)
For example, using a stainless steel foil as a substrate, the structure of the secondary battery 30 according to the embodiment is manufactured in the form of a sheet. After that, the sheets may be laminated to produce a secondary battery 30 having a required capacity.

For example, by facing the second electrode (upper electrode) of two sheets, inserting an electrode (thin metal leaf) between them, and stacking the two sheets in multiple layers, a secondary battery with the required capacity is manufactured. You may. After laminating, it may be sealed with a laminating or the like.

[Other embodiments]
As mentioned above, some embodiments have been described, but the statements and drawings that form part of the disclosure are exemplary and should not be understood as limiting. This disclosure will reveal to those skilled in the art various alternative embodiments, examples and operational techniques.

As described above, the present embodiment includes various embodiments not described here.

The secondary battery of this embodiment can be used for various consumer devices and industrial devices, and is a system application capable of transmitting various sensor information such as a communication terminal and a secondary battery for a wireless sensor network with low power consumption. It can be applied to a wide range of application fields such as secondary batteries for.

12 ... First electrode (E1)
14 ... First oxide semiconductor layer (TIO ₂ layer)
16 ... First charging layer (TiO ₂ / SiO ₂ )
18 ... Second charging layer (buffer layer)
20 ... Charging layer (16.18)
22 ... Hydroxide layer (Ni (OH) ₂ layers)
22C, 22D ... Ni (OH) ₂ / NiOOH layer 22F ... NiOOH layer 24 ... Third oxide semiconductor layer (NiO layer)
26 ... Second electrode (E2)
30 ... Secondary battery 32 ... Voltage source 34 ... Ammeter 36 ... Voltage meter 38 ... Resistance 40 ... Control device 42 ... Load _VA ... Pulse voltage R ... Resistance between the first electrode and the second electrode

Claims (10)

The first conductive type first oxide semiconductor layer and
A first charging layer arranged on the first oxide semiconductor layer and composed of a first insulator and a first conductive type second oxide semiconductor,
A second charging layer with a second insulator and a conductivity adjuster,
The second conductive type third oxide semiconductor layer arranged on the first charging layer and
It is a metal hydroxide that is arranged between the second charging layer and the third oxide semiconductor layer and constitutes the third oxide semiconductor layer, and is oxyhydroxylated with the metal hydroxide by an electric field. With a hydroxide layer that has the property of changing between objects ,
The third oxide semiconductor layer includes nickel oxide (NiO).
A secondary battery characterized in that the hydroxide layer comprises at least one of nickel hydroxide (Ni (OH) ₂ ) and nickel oxyhydroxide (NiOOH) . The secondary battery according to claim 1, wherein the second insulator comprises SiO ₂ , and the conductivity adjusting material comprises SnO _x . The secondary battery according to claim 1 or 2, wherein the second insulator comprises a SiO _x formed from silicone oil. The second oxide semiconductor according to any one of claims 1 to 3, wherein the second oxide semiconductor comprises at least one oxide selected from the group consisting of oxides of Ti, Sn, Zn, or Mg. Secondary battery. The secondary battery according to any one of claims 1 to 4, wherein the conductivity adjusting material comprises a first conductive type semiconductor or an oxide of a metal. The invention according to any one of claims 1 to 5, wherein the conductivity adjusting material comprises at least one oxide selected from the group consisting of oxides of Sn, Zn, Ti, or Nb. Secondary battery. The secondary battery according to any one of claims 1 to 6, wherein the first insulator comprises SiO ₂ , and the second oxide semiconductor comprises TiO ₂ . The hydroxide layer has a laminated structure in which both nickel hydroxide (Ni (OH) ₂ ) and nickel oxyhydroxide (NiOOH) are mixed, and the nickel hydroxide (Ni (OH) ₂ ) is the first. The secondary battery according to any one of claims 1 to 7 , wherein the nickel oxyhydroxide (NiOOH) is in contact with the third oxide semiconductor layer and is in contact with the second charging layer. Claims 1 to 8 are characterized in that the hydroxide layer is provided with nickel oxyhydroxide (NiOOH) when fully charged and is provided with nickel hydroxide (Ni (OH) ₂ ) when fully discharged. The secondary battery according to any one of the above items. The secondary battery according to any one of claims 1 to 9 , wherein the first charging layer has a porous structure.

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