JP7244386B2 - Semiconductor battery, negative electrode material, positive electrode material, and method for manufacturing semiconductor battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to a semiconductor battery that is a primary battery or a secondary battery, a method for manufacturing the same, and a negative electrode material and a positive electrode material used for the semiconductor battery.

Chemical batteries, typified by lithium ion batteries (LIBs), are used in a wide variety of applications such as portable equipment, electric vehicles (EVs), and power storage.

However, especially for electric vehicle applications, lithium-ion batteries cannot be expected to have higher energy densities than at present. Lithium ion batteries have the following problems.
(1) Energy density: In order to achieve the performance of an electric vehicle comparable to that of a gasoline vehicle, an energy density two to three times that of current lithium-ion batteries is required.
(2) Durability: Lithium ions are repeatedly inserted into and detached from the positive electrode active material and the negative electrode active material by charging and discharging, so that the skeletons of the positive electrode active material and the negative electrode active material gradually collapse, or the reactivity is high. A long life cannot be expected due to the gradual deterioration of the positive electrode active material and the negative electrode active material due to the electrolyte.
(3) Safety: The electrolyte is flammable. There is a risk of explosion or fire due to internal gas generation due to overcharging or short circuit.
(4) Cost: Expensive substances such as lithium, cobalt, and nickel are used as raw materials.

Considering the recent situation related to lithium-ion batteries, the development of all-solid-state batteries, which are expected to have high energy density, is active. do not have.

Semiconductor batteries have also been developed in which charge and discharge are realized by the movement of electrons and holes without the movement of ions (Patent Documents 1 and 2). A semiconductor battery accumulates electrons and holes in an energy level and releases the electrons and holes from the energy level to charge and discharge.

JP 2018-101560 A JP 2019-67512 A WO2018/225855

Seisuke Koko, "Research on resistance change memory using oxygen vacancies in aluminum oxide film", Doctoral dissertation, Graduate School of Engineering, Osaka University, 11094/50511 (2014)

As a result of extensive studies, the present inventors have realized a so-called charging/discharging function in a pn junction using the p-type semiconductor described in Patent Document 3 and the n-type semiconductor described in Non-Patent Document 1. As a result, they have invented a semiconductor battery using the p-type semiconductor and the n-type semiconductor.

An object of one embodiment of the present invention is to realize a high-performance semiconductor battery.

In order to solve the above problems, a semiconductor battery according to an aspect of the present invention is made of oxygen-excess aluminum oxide containing excess oxygen, and is capable of accumulating and releasing holes appearing in the bandgap due to excess oxygen. An n-type semiconductor composed of a positive electrode material that is a p-type semiconductor having a conductive level and an oxygen-deficient aluminum oxide that lacks oxygen and has a conductive level capable of storing and releasing electrons that appears in the bandgap due to oxygen deficiency. and a negative electrode material.

An object of one aspect of the present invention is to realize a high-performance semiconductor battery.

1 is a schematic cross-sectional view of a sample used for producing negative electrode material and positive electrode material according to an embodiment of the present invention; FIG. 1 is a schematic configuration diagram of an apparatus used for producing the negative electrode material and the positive electrode material; FIG. It is a schematic sectional drawing which shows the electrode structure of the said negative electrode material and positive electrode material. It is a schematic sectional drawing which shows the electrode structure of the said negative electrode material and positive electrode material. It is a schematic sectional drawing which shows the electrode structure of the said negative electrode material and positive electrode material. It is a schematic sectional drawing which shows the electrode structure of the said negative electrode material and positive electrode material. It is a schematic sectional drawing for demonstrating the manufacturing process of the said electrode structure. It is a schematic sectional drawing for demonstrating the manufacturing process of the said electrode structure. It is a schematic sectional drawing for demonstrating the manufacturing process of the said electrode structure. It is a schematic sectional drawing for demonstrating the manufacturing process of the said electrode structure. It is a schematic diagram for demonstrating the said electrode structure preparation process. It is a schematic diagram for demonstrating the said electrode structure preparation process. It is a schematic diagram for demonstrating the said electrode structure preparation process. It is a schematic diagram for demonstrating the said electrode structure preparation process. 4 is a graph showing charge/discharge characteristics of a semiconductor battery according to an embodiment of the present invention; 4 is a graph showing charge/discharge characteristics of a semiconductor battery according to an embodiment of the present invention; It is a schematic diagram for demonstrating the principle of operation in the said semiconductor battery. It is a schematic diagram for demonstrating the principle of operation in the said semiconductor battery. It is a schematic diagram for demonstrating the principle of operation in the said semiconductor battery. It is a schematic diagram for demonstrating the principle of operation in the said semiconductor battery. 4 is a graph showing current (I)-voltage (V) characteristics of the semiconductor battery according to Example 1; 4 is a graph showing charge/discharge characteristics of the semiconductor battery. 5 is a graph showing current (I)-voltage (V) characteristics of a semiconductor battery according to Example 2; 4 is a graph showing charge/discharge characteristics of the semiconductor battery.

An embodiment of the present invention will be described in detail below. In addition, in each embodiment, the same code|symbol is attached|subjected to the same part, and what attached|subjected the same code|symbol in drawing abbreviate|omits description for the second time suitably. In addition, the dimensions, materials, shapes, relative arrangements, processing methods, etc. of the configuration described in each embodiment are merely examples, and the technical scope of the present invention should not be construed as limited by these descriptions. Furthermore, the drawings are schematic, and dimensional ratios and shapes may differ from the actual ones.

[Negative electrode material and positive electrode material]
A negative electrode material and a positive electrode material according to one embodiment of the present invention will be described. The negative electrode material and the positive electrode material are produced by a method of sparking an aluminum oxide film (hereinafter referred to as "spark method"). An example of fabrication by the spark method is shown below.

(sample)
FIG. 1 is a schematic cross-sectional view of a sample used to make anode and cathode materials. As shown in FIG. 1, a sample is prepared by coating the surface of a metal aluminum substrate 1 with an aluminum oxide film 2 . The surface of the metal aluminum substrate 1 is previously coated with an aluminum oxide film 2 . Methods of coating the aluminum oxide film 2 include a method using a natural oxide film, a sputtering method, an anodic oxidation method, an air heating method, and a boehmite treatment method. The coated aluminum oxide film 2 contains water and has a film quality that cannot be said to be pure aluminum oxide. For example, the molecular formula of boehmite is Al ₂ O ₃ .H ₂ O and contains one molecule of water. The film thickness of the aluminum oxide film 2 is set to 2 nm to 100 nm.

Here, aluminum oxide, aluminum hydroxide, and the like can be mentioned as film materials for producing negative electrode materials and positive electrode materials of semiconductor batteries by the spark method. Furthermore, a compound such as boehmite containing water molecules in aluminum oxide can also be used.

Moreover, the metal ion species contained in the film material for producing the negative electrode material and the positive electrode material by the spark method may be different from the metal that is the base material with which the film material is coated. For example, the above film material may be formed by sputtering on metal aluminum or platinum as a base material. Alternatively, the film material may be obtained by chemically converting the surface of metal aluminum as a base material and coating the surface with the above film material.

When the substrate is metallic aluminum, an aluminum alloy can be used as the metallic aluminum. That is, in addition to 4N or higher high-purity aluminum and pure aluminum (1000 series), Al--Mn alloy (3000 series), Al--Si alloy (4000 series), Al--Mg alloy (5000 series), Al-- A Cu--Mg alloy (2000 series), an Al--Mg--Si alloy (6000 series), or an Al--Zn--Mg alloy (7000 series) can be used.

Also, as the material of the probe 5 for contacting the above-described film material and sparking, highly conductive substances such as platinum, stainless steel, copper, and carbon can be used. A material with high heat resistance is preferable because the temperature becomes high due to the spark. Although platinum is an excellent material, it is expensive. A material obtained by plating the outermost surface of a silicon core material with platinum may be used.

(Device)
FIG. 2 is a schematic configuration diagram of an apparatus used to prepare the negative electrode material and the positive electrode material. In the apparatus shown in FIG. 2, a semiconductor battery composed of a negative electrode material, a positive electrode material, and a separator can be produced using a contacting AFM (Atomic Force Microscope), and the produced semiconductor battery can be evaluated. A platinum-plated probe 5 is attached to the tip of the cantilever 6 . The metal aluminum substrate 1 is fixed to the sample fixing plate 4 , and the tip of the probe 5 is brought into contact with the aluminum oxide film 2 on the metal aluminum substrate 1 . A voltage of +5 V to +60 V is applied to the metal aluminum substrate 1 with respect to the probe 5 in the atmosphere for a certain period of time to cause dielectric breakdown due to sparks, thereby fabricating a semiconductor battery.

A voltage meter 8 is used to measure the voltage during fabrication of the semiconductor battery. During this measurement, it is important to control the amount of electricity generated by the spark. In practice, the resistance value of the current limiting resistor 10 is appropriately changed, the current is measured using the ammeter 9, and the control is performed based on the measurement result. If a measuring device capable of observing short-term changes in voltage or current is used in combination with the voltmeter 8 or ammeter 9, control becomes easier. For example, an oscilloscope may be used.

(structure)
Each size of the negative electrode material 11 and the positive electrode material 12 produced by the spark method was 0.2 μm to 10 μm in diameter and 10 nm to 10 μm in thickness. 3 to 6 are schematic cross-sectional views showing electrode structures of the negative electrode material 11 and the positive electrode material 12. FIG.

The electrode structure shown in FIG. 3 was produced by the spark method with a spark voltage of 20 V and a current limiting resistor 10 of 400 MΩ. A negative electrode material 11 made of an n-type semiconductor is formed on the metal aluminum substrate 1 side. A positive electrode material 12 made of a p-type semiconductor is formed on the side of the probe 5 having a tip made of platinum. As shown in FIG. 3, one main surface of the negative electrode material 11 and one main surface of the positive electrode material 12 facing the one main surface are surface-bonded.

However, in FIG. 3, it is described as if one main surface of the negative electrode material 11 and one main surface of the positive electrode material 12 are planarly bonded. However, in reality, one main surface of the negative electrode material 11 and one main surface of the positive electrode material 12 are each an uneven surface curved by the impact of the spark, and the uneven surfaces are often joined together. . This point is the same for FIGS. 4 to 6 as well.

The electrode structure shown in FIG. 4 was produced by the spark method with a spark voltage of 20 V and a current limiting resistor 10 of 300 MΩ. A negative electrode material 11 made of an n-type semiconductor is formed on the metal aluminum substrate 1 side. A positive electrode material 12 made of a p-type semiconductor is formed on the side of the probe 5 having a tip made of platinum.

However, the electrode structure shown in FIG. 4 differs from the electrode structure shown in FIG. Another point is that the separator 13 made of a stoichiometric aluminum oxide film is manufactured with a thickness of 1 nm to 10 nm. A tunnel effect occurs by reducing the thickness of the separator 13 , and as a result, a tunnel current caused by at least one of electrons and holes can flow through the separator 13 . In the electrode structure shown in FIG. 4, the current limiting resistor 10 is lowered from 400 MΩ (the resistance value when the electrode structure of FIG. 3 is manufactured) to 300 MΩ, thereby increasing the current during sparking. The amount of electricity generated during the production of the material 12 increases. Due to the increase in the amount of electricity, the negative electrode material 11 and the positive electrode material 12 electrolyzed with molten salt are mixed in a plane, and the mixed portion becomes a stoichiometric aluminum oxide film that is an insulator, that is, the separator 13. .

The electrode structure shown in FIG. 5 was produced by the spark method with a spark voltage of 20 V and a current limiting resistor 10 of 100 MΩ. A positive electrode material 12 made of a p-type semiconductor is formed on the metal aluminum substrate 1 side. A negative electrode material 11 made of an n-type semiconductor is formed on the side of the probe 5 having a tip made of platinum. As shown in FIG. 5, one main surface of the negative electrode material 11 and one main surface of the positive electrode material 12 facing the one main surface are surface-bonded. The electrode structure shown in FIG. 5 differs from the electrode structure shown in FIG. 3 in that the manufacturing positions of the negative electrode material 11 and the positive electrode material 12 are reversed.

The electrode structure shown in FIG. 6 was produced by the spark method with a spark voltage of 20 V and a current limiting resistor 10 of 60 MΩ. A positive electrode material 12 made of a p-type semiconductor is formed on the metal aluminum substrate 1 side. A negative electrode material 11 made of an n-type semiconductor is formed on the side of the probe 5 having a tip made of platinum.

However, the electrode structure shown in FIG. 6 differs from the electrode structure shown in FIG. Another point is that the separator 13 made of a stoichiometric aluminum oxide film is manufactured with a thickness of 1 nm to 10 nm. In the electrode structure shown in FIG. 6, the current limiting resistor 10 is lowered from 100 MΩ (the resistance value when the electrode structure of FIG. 5 was produced) to 60 MΩ, thereby increasing the current during sparking. The amount of electricity generated during the production of the material 12 increases. Due to the increase in the amount of electricity, the positive electrode material 12 and the negative electrode material 11 electrolyzed with molten salt are mixed in a planar manner, and the mixed portion becomes a stoichiometric aluminum oxide film which is an insulator, that is, the separator 13 . The electrode structure shown in FIG. 6 differs from the electrode structure shown in FIG. 4 in that the positive electrode material 12 and the negative electrode material 11 are produced in opposite positions.

Here, the manufacturing process of the electrode structure shown in FIGS. 5 and 6 will be described. In particular, the manufacturing positions of the negative electrode material 11 and the positive electrode material 12 in the electrode structures shown in FIGS. 5 and 6 are opposite to the manufacturing positions of the negative electrode material 11 and the positive electrode material 12 in the electrode structures shown in FIGS. Consider the mechanism of

7 to 10 are schematic cross-sectional views for explaining the manufacturing process of the electrode structure shown in FIGS. 5 and 6. FIG. First, the case where the spark voltage is 20 V and the current limiting resistor 10 is 100 MΩ will be described with reference to FIGS. 7 to 9. FIG.

As shown in FIG. 7, production of the positive electrode material 12 and the negative electrode material 11 is started by molten salt electrolysis using sparks. More specifically, the production direction of the negative electrode material 11 is the direction b1 from the metal aluminum substrate 1 side to the probe 5 side, and the production direction of the positive electrode material 12 is from the probe 5 side to the metal aluminum substrate 1 side. The heading direction is a1. By lowering the current limiting resistor 10 from 400 MΩ (the resistance value at the time of fabricating the electrode structure in FIG. 3) to 100 MΩ, the current at the time of sparking increases, and as a result, the amount of electricity in the molten salt electrolysis increases.

As shown in FIG. 8, due to the increase in the amount of electricity, the negative electrode material 11 produced on the metal aluminum substrate 1 side reaches the probe 5 side, while the positive electrode material 12 produced on the probe 5 side reaches the metal aluminum substrate. Reach side 1. Even after the negative electrode material 11 reaches the probe 5 side and the positive electrode material 12 reaches the metal aluminum substrate 1 side, the production of the positive electrode material 12 and the negative electrode material 11 is continued by continuing the energization.

However, in the vertical direction (that is, direction a1 and direction b1) in FIG. As a result, the manufacturing direction of the positive electrode material 12 and the negative electrode material 11 is the horizontal direction in FIG. More specifically, the manufacturing direction of the negative electrode material 11 changes from the direction b1 to the directions b2 and b3, and the manufacturing direction of the positive electrode material 12 changes from the direction a1 to the directions a2 and the direction a3.

In this way, as shown in FIG. 9, an electrode structure in which one main surface of the positive electrode material 12 and one main surface of the negative electrode material 11 facing the one main surface are surface-bonded, that is, as shown in FIG. The electrode structure shown will be fabricated.

Next, the case where the current limiting resistor 10 is set to 60 MΩ will be described with reference to FIGS. 7 to 10. FIG. By reducing the current limiting resistor 10 to 60 MΩ, the current at the time of sparking is further increased, and as a result, the amount of electricity in the molten salt electrolysis is further increased. As shown in FIG. 10, due to an increase in the amount of heat generated due to an increase in the amount of electricity, the negative electrode material 11 and the positive electrode material 12 in the molten salt electrolysis are mixed in a plane, and the mixed portion is an insulator. A typical aluminum oxide film, that is, the separator 13 is formed. That is, the electrode structure shown in FIG. 6 is produced. The manufacturing process in FIGS. 7 to 9 is the same as the case where the current limiting resistor 10 is set to 100 MΩ, so the description will not be repeated.

(Electrode structure creation process)
The mechanism of the electrode structure fabrication process will be considered below. 11 to 14 are schematic diagrams for explaining the electrode structure fabrication process for obtaining the electrode structure shown in FIG. 3 or FIG.

During sparking, a positive voltage is applied to the metal aluminum substrate 1 side and a negative voltage is applied to the probe 5 side in the atmosphere. FIG. 11 shows a state in which the aluminum oxide film 2, which is an insulator, is subjected to molten salt electrolysis by sparks. During sparking, a spark current flows for a short period of time. While the spark current is flowing, the aluminum oxide film 2 reaches a temperature higher than its melting point and becomes a molten salt. The melting point of the aluminum oxide film 2 is 2072.degree. At temperatures above the melting point, molten salt electrolysis occurs on the metal aluminum substrate 1 side, ie, the anode side, according to formula (1), and on the probe 5 side, ie, the cathode side, according to formula (2). _O2 is atmospheric oxygen.
Al→Al ³⁺ +3e (1)
O ₂ +4e→2O ²⁻ (2)
Al ³⁺ and O ²⁻ are accumulated in the aluminum oxide film 2 according to formula (3) by molten salt electrolysis occurring according to formula (1) on the anode side and according to formula (2) on the cathode side. The accumulation layer made up of these accumulations gradually thickens, and the film thickness of the aluminum oxide film 2 increases as shown in FIG.
4Al+3O ₂ →4Al ³⁺ +6O ²⁻ (3)
After the spark ends, the temperature of the aluminum oxide film 2 drops. The temperature ramp-down rate is not completely uniform within the accumulator layer, and solid and liquid are intermixed and partially solidified to produce Al ₂ O ₃ . The portion where the molten salt electrolysis state remains is ionized. Solid Al ₂ O ₃ is an insulator at room temperature, but has electronic conductivity at high temperatures near its melting point. Either or both of these two reasons will continue the molten salt electrolysis according to equation (1) and the molten salt electrolysis according to equation (2) as shown in FIG.

On the metallic aluminum substrate 1 side, O ²⁻ ions decrease and Al ³⁺ ions increase, ie Al ³⁺ ions become excessive, resulting in a new conductivity level in the accumulation layer in order to maintain electrical neutrality. level, ie the donor level, appears. On the other hand, on the probe 5 side, the Al ³⁺ ions decrease and the O ²⁻ ions increase, that is, the O ²⁻ ions become excessive, resulting in a new conductivity level in the accumulation layer in order to maintain electrical neutrality. level, ie the acceptor level, appears.

Further, when the temperature of the aluminum oxide film 2 drops to room temperature, the accumulation layers shown in FIGS. More specifically, on the metal aluminum substrate 1 side, a negative electrode material 11 made of oxygen-deficient aluminum oxide, i.e., an n-type semiconductor, is produced, and on the probe 5 side, oxygen-excessive aluminum oxide, i.e., p A positive electrode material 12 made of a type semiconductor is produced.

Here, when spark current flows with an appropriate amount of electricity, the negative electrode material 11 and the positive electrode material 12 are surface-bonded, and the semiconductor battery shown in FIG. 13 is produced.

On the other hand, when the spark current flows with a slightly large amount of electricity, at the interface between the negative electrode material 11 and the positive electrode material 12, one main surface sides of the negative electrode material 11 and the positive electrode material 12, which face each other, are mixed during the molten salt electrolysis. A matching, insulating stoichiometric aluminum oxide, ie separator 13, is produced. As a result, a semiconductor battery in which the separator 13 is sandwiched between the negative electrode material 11 and the positive electrode material 12 as shown in FIG. 14 is produced. The reaction in the electrode structure fabrication process for obtaining the electrode structure shown in FIG. 5 or 6 is the same as the reaction in the electrode structure fabrication process for obtaining the electrode structure shown in FIG. 3 or 4 .

Also, instead of the spark method described above, a method of producing the negative electrode material and the positive electrode material by laser technology and sputtering technology (hereinafter referred to as "laser-sputtering method") may be used. The laser-sputtering method will be described below.

First, an aluminum oxide base material such as alumina or sapphire is irradiated with a laser such as a carbon dioxide laser or a disk laser in the atmosphere or in an oxygen-containing gas to heat the aluminum oxide base material to a temperature above its melting point. When the temperature of the aluminum oxide substrate reaches the melting point or higher, the anode made of aluminum and the cathode made of platinum are brought into contact with each other at different places on the molten aluminum oxide substrate, and current is passed between the anode and the cathode. . Molten salt electrolysis occurs at the above-mentioned locations by the flow of electric current, and as a result, an n-type semiconductor made of oxygen-deficient aluminum oxide, that is, a negative electrode material is produced on the anode side, and an oxygen-excessive aluminum oxide is produced on the cathode side. A p-type semiconductor, ie, cathode material, is fabricated.

Next, the negative electrode material and the positive electrode material are separated and taken out using a sputtering method. A large number of aluminum oxide substrates on which the negative electrode material and the positive electrode material are produced are prepared by the above method, and a large number of holes are formed so that only the negative electrode material portion of each aluminum oxide substrate is exposed and other portions are covered. Mask with a sheet that has been opened. By setting the aluminum oxide base material in a sputtering apparatus and performing sputtering in an argon gas atmosphere, only the negative electrode material of the aluminum oxide base material is released into the gas phase. It is deposited on another aluminum oxide substrate. In this way, a large amount of the negative electrode material is taken out individually and used as a single raw material for the negative electrode material. The same applies to the positive electrode material.

As the raw material for the separator, for example, stoichiometric insulating aluminum oxide and insulating silicon oxide can be used.

The above-described negative electrode material raw material is used as a negative electrode material target material, the above-described positive electrode material raw material is used as a positive electrode material target material, and the above-described separator raw material is used as a separator target material.

First, a negative electrode material is deposited on an aluminum plate serving as a negative electrode current collector by a sputtering method using a target material for a negative electrode material. A separator is deposited on the aluminum plate on which the negative electrode material is deposited by a sputtering method using a separator target material. A cathode material is deposited on the aluminum plate on which the separator is deposited by a sputtering method using a cathode material target material. The aluminum plate on which the positive electrode material is deposited is coated with platinum, which serves as a positive electrode current collector.

In this way, a semiconductor battery, which is a secondary battery in which the negative electrode current collector, the negative electrode material, the separator, the positive electrode material, and the positive electrode current collector are laminated in this order, can be produced.

[Semiconductor battery]
(Operating principle)
The operating principle of the semiconductor battery will be described.

The negative electrode material 11 is an n-type semiconductor that is oxygen-deficient aluminum oxide. The oxygen-deficient aluminum oxide is amorphous or amorphous containing polycrystals. The n-type semiconductor, which is amorphous oxygen-deficient aluminum oxide, is described in detail in Non-Patent Document 1.

The molecular formula for oxygen-deficient aluminum oxide is
Al ₂ O _3-n (Vo ^X ) _n (4)
is.

Here, Vo ^X denotes oxygen-deficient vacancies. An aluminum oxide molecule is a substance having stronger ionic bonds than covalent bonds, and it is considered that Al ³⁺ and O ²⁻ are strongly bonded.

When one O ²⁻ is depleted, two electrons enter an O ²⁻ deficient portion (hereinafter referred to as “Vo vacancy”) to maintain electrical neutrality. This state is the state of X=0, and V _O ⁰ in equation (4). In the state of X=+1 in which one electron enters the V 2 _O vacancy, Equation (4) becomes V _{2 O} ⁺¹ . In addition, in the state of X=+2 where there are no electrons in V _{2 O} vacancies, Equation (4) becomes V _{2 O} ⁺² .

When the substance represented by formula (4) is a crystal, it has almost no conductive levels of _VO ⁰ , _VO ⁺¹ , and _VO ⁺² in the bandgap, so that they are almost insulators and accumulate a large amount of electrons. you can't.

In contrast, if the material represented by formula (4) is amorphous, or amorphous containing polycrystals, it exhibits a V 2 _O ⁺¹ conduction level in the bandgap. Since the conductive level and the Fermi level overlap, the substance represented by the formula (4) is in a metallic state, and extremely large electrons are accumulated. Non-Patent Document 1 indicates that the maximum electron carrier concentration when electrons are accumulated to the maximum is on the order of 10 ²¹ cm ⁻³ . It has been found that the negative electrode material 11 produced by the inventors by the spark method has a maximum electron carrier concentration of 10 ²² cm ⁻³ or more, which is one order of magnitude larger. Since V ₀ ⁰ and V ₀ ⁺² have almost no conductive level in the bandgap, they are almost insulators and cannot accumulate a large amount of electrons.

In addition, at the conduction level of V ₀ ⁺¹ , one electron can be put into a Vo vacancy. Therefore, the Vo vacancies will have a positive charge of +1. Therefore, a capacitor is generated between the negative charges of the electrons entering the Vo vacancies and the positive charges of the Vo vacancies. It is believed that this capacitor also contributes to charge storage. Since no electrons enter the Vo vacancies at the V ₀ ⁺² conduction level, it is considered that there is substantially no capacitor component in the Vo vacancies.

In this way, the negative electrode material according to the present embodiment can have a much larger discharge quantity of electricity (Ah/kg) than the negative electrode material of a chemical battery typified by a lithium ion battery.

The negative electrode material 11 consists of V ₀ ⁺¹ and V ₀ ⁺² . By adjusting the bias voltage applied to the negative electrode material 11, the ratio between V ₀ ⁺¹ and V ₀ ⁺² can be appropriately adjusted. In FIG. 15, the horizontal axis indicates the electron energy eV _nb (eV) that is the product of the negative bias voltage V _nb (V) and the elementary charge e (large on the left side and small on the right side), and the vertical axis indicates the energy of the semiconductor battery. The current J (A) during charging (bottom) and discharging (top) is shown. Note that FIG. 15 shows a case where the semiconductor battery is a secondary battery.

Let E _nj (eV) be the conduction level of V _O ⁺¹ . When eV _nb =E _nj is first set and then eV _nb is increased from E _nj , the speed of the reduction reaction in equation (5) increases sharply and the current J increases, as indicated by arrow c1. , E _nj and electrons are accumulated in the neighboring levels.
_VO ⁺² +e→VO ₊ ¹ (5)
The current J reaches a peak when the stored electrons are almost full. Furthermore, when _eVnb is increased, the current J abruptly decreases to zero as indicated by arrow c2.

Then, as shown by arrow c3, _eVnb is decreased and the current J remains zero up to _Enj . That is, the relationship between eV _nb and current J becomes hysteresis.

Furthermore, when _eVnb is decreased from _Enj , the rate of the oxidation reaction in _Eq . Electrons stored in the site are released.
_VO ⁺² +e←VO ₊ ¹ (6)
The current J eventually reaches a peak, and when _eVnb is further decreased, the current J sharply decreases as indicated by an arrow d2. When the accumulated electrons are completely discharged, the current J becomes substantially zero. Again, increasing _eVnb causes the current J to remain substantially zero up to _Enj , as indicated by arrow d3. That is, the relationship between eV _nb and current J becomes hysteresis.

In the negative electrode material according to the present embodiment, as described above, a reduction reaction occurs during charging and an oxidation reaction occurs during discharging, in which electrons move without ion movement. This point is also completely different from negative electrode materials for chemical batteries represented by conventional lithium ion batteries.

The positive electrode material 12 is a p-type semiconductor that is oxygen-excess aluminum oxide. The oxygen-excess aluminum oxide is amorphous or amorphous containing polycrystals. The p-type semiconductor, which is oxygen-excess aluminum oxide, is described in detail in Patent Document 3.

If the oxygen-excess type aluminum oxide is represented by the molecular formula,
_{Al2O3 (EOX ) n} ⁽ 7)
is.

Here, E _O ^X denotes excess oxygen. Aluminum oxide molecules are substances having stronger ionic bonds than covalent bonds, and it is believed that Al ³⁺ and O ²⁻ are strongly bonded.

When one O ²⁻ increases, two holes enter the O ²⁻ excess portion (hereinafter referred to as “E 2 _O excess portion”) in order to maintain electrical neutrality. This state is the state of X=0, and E _O ⁰ in equation (7). Equation (7) becomes E 2 _O −1 in the state of X=−1 in which one hole enters the E ² _O excess portion. In addition, in the state of X=-2 where there are no holes in the E _{2 O} excess portion, Equation (7) becomes E _{2 O} ^-2 .

When the substance represented by the formula (7) is a crystal, it has almost no conductive levels of E ₀ ⁰ , E ₀ ⁻¹ , and E ₀ ⁻² in the bandgap. cannot be stored in

On the other hand, if the material represented by formula (7) is amorphous or amorphous containing polycrystals, it exhibits an E _{2 O} ⁻¹ conduction level in the bandgap. Since the conductive level and the Fermi level overlap, the substance represented by the formula (7) is in a metallic state, and extremely large holes are accumulated. It has been found that the positive electrode material 12 produced by the present inventors by the spark method has a maximum hole carrier concentration of 10 ²² cm ⁻³ or more. Since E ₀ ⁰ and E ₀ ^-2 have almost no conductive level in the bandgap, they are almost insulators and cannot accumulate a large amount of holes.

Also, at the E 2 _O ⁻¹ conduction level, one hole can be inserted into the E 2 _O excess. Therefore, the E 2 _O excess will have a negative charge of −1. Therefore, a capacitor is formed between the positive charge of holes entering the E _{2 O} excess and the negative charge of the E _{2 O} excess. It is believed that this capacitor also contributes to charge storage. Since holes do not enter the E _{2 O} excess portion at the E 2 O ^-2 conduction level, it is considered that there is substantially no capacitor component in the E 2 _O excess portion.

In this way, the positive electrode material according to the present embodiment can have a discharge quantity of electricity (Ah/kg) much larger than that of the positive electrode material of chemical batteries represented by lithium ion batteries.

The cathode material 12 consists of E _{2 O} ^-1 and E 2 _O ^-2 . By adjusting the bias voltage applied to the positive electrode material 12, the ratio of E 2 _O ^-1 and E _{2 O} ^-2 can be appropriately adjusted. In FIG. 16, the horizontal axis indicates the electron energy eV _pb (eV) which is the product of the positive electrode side bias voltage V _pb (V) and the elementary charge e (large on the left side, small on the right side), and the vertical axis indicates the energy of the semiconductor battery. The current J (A) during charging (bottom) and discharging (top) is shown. Note that FIG. 16 shows a case where the semiconductor battery is a secondary battery.

Let E _pj (eV) be the conductivity level of E _O ⁻¹ . When eV _pb =E _pj is first set and then eV _pb is decreased from E _pj , the rate of the oxidation reaction in equation (8) increases sharply and the current J increases, as indicated by arrow c1. , _Epj , and in its neighboring levels.
E _O ⁻² +h→E _O ⁻¹ (8)
The current J reaches a peak when the stored holes are almost full. When _eVpb is further decreased, the current J abruptly decreases to zero as indicated by arrow c2.

Then, as _eVpb is increased, current J remains zero up to _EpJ , as indicated by arrow c3. That is, the relationship between _eVpb and current J becomes hysteresis.

Furthermore, when _eVpb is increased from _Epj , the speed of the reduction reaction in _Eq . Holes that have accumulated within the site are released.
_EO ⁻² +h← _EO ⁻¹ (9)
Current J eventually reaches a peak, and when _eVpb is further increased, current J rapidly decreases as indicated by arrow d2. When the accumulated holes are completely discharged, the current J becomes substantially zero. Decreasing eV _pb causes the current J to remain zero up to _Epj , as indicated by arrow d3. The relationship between _eVpb and current J becomes hysteresis.

In the positive electrode material according to the present embodiment, as described above, an oxidation reaction occurs during charging and a reduction reaction occurs during discharging, in which holes move without ion movement. It can be said that this point is also completely different from positive electrode materials for chemical batteries represented by conventional lithium ion batteries.

Note that the larger the n of the negative electrode material 11 in the formula (4) and the larger the n of the positive electrode material 12 in the formula (7), the greater the number of electrons and holes accumulated in the conductive level. For example, when n=1.5, the maximum number of electrons and holes is approximately 3×10 ²² cm ⁻³ in terms of carrier concentration. As n increases, the electric charge (As) of the battery increases.

Also, the negative electrode material and the positive electrode material are in contact with the negative electrode current collector and the positive electrode current collector, respectively. Depending on the materials of the negative electrode current collector and the positive electrode current collector, each of them may have a Schottky barrier with the negative electrode current collector and the positive electrode current collector. This Schottky barrier occurs between the electron energy (eV _nb or eV _pb ), which is the bias voltage multiplied by the elementary charge e, and the conduction level (E _nj or E _pj ).

Specifically, it appears as a phenomenon that the slope of the steep straight line becomes smaller near _Enj in FIG. 15 or the slope of the steep straight line becomes smaller near _Epj in FIG.

An example of IV characteristics of a semiconductor battery is shown in FIG. 23, which will be described later. The horizontal axis is the voltage of the semiconductor battery, the positive side of the vertical axis is the charging current, and the negative side is the discharging current. There is a Schottky barrier between the anode material and the anode current collector and between the cathode material and the cathode current collector, respectively. Therefore, even if the voltage is increased from the "start" voltage VS at the time of opening, the charging current will not rise sharply for a while, and a gradual rise in the current with a small slope will be observed.

Here, the battery voltage in the semiconductor battery according to the embodiment of the present invention will be explained.

As described above, in the anode material, E _nj (eV) coincides with the Fermi level E _Fn (eV) of the anode material. Also, in the positive electrode material, E _pj (eV) coincides with the Fermi level E _Fp (eV) of the positive electrode material. The work function of the negative electrode material is W _Fn (eV), and the work function of the positive electrode material is W _Fp (eV).

The open-circuit voltage V _O (V) can be expressed as follows. However, it is assumed that electrons exist in the conduction level of _Enj and holes exist in the conduction level of _Epj .
V _O =(W _Fp −W _Fn )/e (10)
The voltage V _C (V) during charging can be expressed as follows. However, E _ch (eV) indicates the electron energy loss at the separator or conductive portion during charging.
V _C =[{W _FP −(eV _pb −E _pj )}−{W _Fn −(eV _nb −E _nj )}+E _ch ]/e
(11)
The voltage V _d (V) during discharge can be expressed as follows. However, E _dis (eV) indicates the electron energy loss in the separator or conductive portion during discharge.
V _d =[{W _FP −(eV _pb −E _pj )}−{W _Fn −(eV _nb −E _nj )}−E _dis ]/e
(12)
(separator)
As described above, the separator is made of insulating stoichiometric aluminum oxide, and a tunneling effect occurs by reducing the thickness of the separator. can be done. However, in the case of the method of successively laminating electrode materials, insulators made of other materials such as silicon oxide can be used.

17 to 20 are schematic diagrams for explaining the principle of operation of a semiconductor battery using band diagrams. 17 is a diagram showing before charging or after discharging, FIG. 18 is a diagram showing during charging, FIG. 19 is a diagram showing during rest, and FIG. 20 is a diagram showing during discharging. In each figure, E _C denotes the bottom of the conduction band, E _F the Fermi level, and E _V the top of the valence band.

17 shows the state before charging or after discharging, and FIG. 19 shows the state during rest after charging, both of which are in the open circuit state. The E _F (same as E _nj ) of the negative electrode material 11 coincides with the E _F (same as E _pj ) of the positive electrode material 12 with the separator 13 interposed therebetween. There is no movement and no current flows. The voltage _VO when the circuit is open is expressed by Equation (10).

FIG. 18 shows the state during charging. Since E _nj is raised to a level higher than E _pj by the charging power source 101 , electrons are accumulated on the E _nj side of the negative electrode material 11 and holes are accumulated on the E _pj side of the positive electrode material 12 . A flow of electrons from the negative electrode material 11 to the positive electrode material 12, a flow of holes from the positive electrode material 12 to the negative electrode material 11, or a flow of both occurs in the separator 13. FIG. The voltage V _C during charging is represented by equation (11), and if (eV _pb -E _pj ) and (eV _nb -E _nj ) are small values and the electron energy loss in the conductive portion is small, Since _Ech is the electron energy loss in the separator 13, the actual _Vc is shown below.
V _C ≈(W _FP −W _Fn +E _ch )/e (13)
FIG. 20 shows the state during discharge. By connecting the discharge resistor 103, _Enj becomes a level lower than _Epj , so that the electrons accumulated on the _Enj side of the negative electrode material 11 are emitted, and the holes accumulated on the _Epj side of the positive electrode material 12 are discharged. is emitted. Electron flow from the positive electrode material 12 to the negative electrode material 11 , hole flow from the negative electrode material 11 to the positive electrode material 12 , or both flows are generated in the separator 13 . The voltage V _d during discharge is expressed by equation (12), where (eV _pb −E _pj ) and (eV _nb −E _nj ) are small values, and if the electron energy loss in the conductive portion is small, E Since _dis is the electron energy loss in the separator 13, the actual _Vd is shown below.
V _d ≈(W _FP −W _Fn −E _dis )/e (14)

EXAMPLES Hereinafter, the present embodiment will be described in more detail with reference to examples, but the present embodiment is not limited to the following examples.

(Production of sample battery)
A sample of a semiconductor battery used for evaluation was produced. As shown in FIG. 1, a sample for producing a sample battery has an aluminum oxide film 2 formed by anodization on the surface of a metal aluminum substrate 1, and a probe 5 on the surface of the aluminum oxide film 2. It is a structure in which the applied platinum plating is laminated.

A more detailed description of the samples is as follows.

The material of the metal aluminum substrate 1 was 1085 (containing 99.85% Al and mainly Fe and Si as other elements), the size was 50 mm×50 mm, and the thickness was about 0.1 mm. As a pretreatment of the metal aluminum substrate 1, the surface of the material was smoothed by electropolishing.

As shown in FIG. 2, a sample battery was produced and evaluated in AFM (Atomic Force Microscope) contacting mode using a scanning probe microscope, model number JSPM-5200 manufactured by JEOL. The cantilever 6 with the probe 5 attached to the tip is manufactured by Budgetsensors, model number Tap190E-G, the tip diameter is about 25 nm, the core material is silicon, and the 5 nm thick chrome plating and the 25 nm thick platinum plating on the surface of the chrome plating are applied. I used what was given. The resonance frequency was 190 kHz. In the sample battery, the tip diameter at which the platinum plating at the tip of the probe 5 contacts the aluminum oxide film 2 is about 25 nm.

A target sample battery was produced by applying a voltage of +20 V to the metal aluminum substrate 1 in air for about 10 seconds to cause sparks to the platinum plating on the aluminum oxide film 2 at the tip of the probe 5 . At this time, it is important to reduce the current caused by the spark. Here, the preamplifier gain was set to 0.1 V/nA to limit the maximum current to 100 nA by setting the circuit resistance to 100 MΩ. The sample battery produced here has the electrode structure shown in FIG.

The size of the produced sample batteries varied, but most of them had a diameter of about 0.2 μm to 2 μm. Also, although the maximum thickness was 20 nm to 100 nm, it is considered that the portion that actually functions as a battery is composed of a portion thinner than the maximum thickness.

The position of the probe 5 was kept in contact with the sample, and the IV characteristics were measured with the circuit in the state shown in FIG. The voltage operation range was -0.20 V to +0.20 V, the filter was 100 Hz, the preamplifier gain was 0.1 V/nA (circuit resistance 100 MΩ), and the voltage clock was 10 ms. The operation time from -0.20V to +0.20V was 5.7s. The maximum current at this setting was +100 nA and the minimum current was -100 nA.

FIG. 21 shows the measurement results of IV characteristics. First, voltage scanning from -0.20 V to +0.20 V (hereinafter referred to as "forward scanning") was performed. The result of forward scanning was the graph along arrow Y21. Immediately after this, reverse voltage scanning (hereinafter referred to as “negative direction scanning”) from +0.20 V to −0.20 V was performed. The result of the negative scan was the graph along arrow X21.

The forward scan results were as follows. From -0.20 V to +0.015 V, the minimum current was -100 nA in the above setting, but at +0.015 V the absolute value of the current rapidly decreased and showed a large slope. There is a small slope from +0.020V to +0.075V. The current value became 0A at +0.04V on the way. From +0.075V to +0.080V, there is a large slope again, and at +0.080V the maximum current at the above setting is +100 nA, and the maximum current continues up to +0.20V.

The negative scan results were as follows. From +0.20 V to +0.070 V, the maximum current was +100 nA in the above setting, but at +0.070 V, the absolute value of the current rapidly decreased and showed a large slope. A small slope was observed from +0.05V to +0.005V. The current value became 0A at +0.04V on the way. From +0.005 V there is a large slope again, with little increase in voltage, reaching the minimum current of -100 nA at the above settings.

What is characteristic of each result of the positive direction scanning and the negative direction scanning is that a bias voltage of +0.04V is generated when the current value is 0A. When the current value is zero in this way, the phenomenon that a bias voltage is generated is not observed in a normal semiconductor device, and it can be said that a semiconductor battery is produced.

FIG. 22 shows a graph in which the horizontal axis represents the amount of electricity (nAs) and the vertical axis represents the voltage (V). The change in the amount of electricity in the voltage range of +0.04V to +0.094V is the so-called "charging characteristic" of the secondary battery. Also, the change in the amount of electricity in the voltage range of +0.04V to 0.00V is the so-called "discharge characteristic" of the secondary battery. From this, it can be said that the manufactured semiconductor battery is a secondary battery. However, it should be noted that FIG. 22 shows only the characteristics, not that the charge stored during "charging" is released during "discharging".

Moreover, the semiconductor battery having the charge/discharge characteristics shown in FIG. 22 has an extremely low cell voltage and is difficult to be used as a practical battery. This low cell voltage is believed to correspond to the built-in voltage produced by the bonding of the positive and negative electrode materials. By inserting the aforementioned separator between the positive electrode material and the negative electrode material, the cell voltage can be greatly increased.

A metal aluminum substrate 1 (1085 material, 12×30 mm, thickness 0.2 mm) was prepared. This sample was immersed in pure water heated to 95° C. to form a boehmite film having a thickness of about 20 nm on the metal aluminum substrate 1 . A manual prober shown in FIG. 2 was prepared. As the probe 5, a platinum wire (H material) having a diameter of 0.2 mm was shaved at its tip to have a diameter of 0.02 mm.

The current limiting resistor 10 was set to 60 MΩ, the output of the current/DC stabilized power supply 7 was set to a constant voltage of 20 V, and voltage was applied after the tip of the probe 5 was brought into contact with the aluminum oxide film 2 on the sample in the air. A spark was generated between the tip of the probe 5 and the metal aluminum substrate 1 . A sample battery having a size of about 10 μm and a thickness of about 2 μm was fabricated at the portion where the tip of the probe 5 was brought into contact.

(IV characteristics)
After the energization was completed, the IV characteristics of the obtained sample battery were measured while the probe 5 was kept as it was. However, the current limiting resistor 10 was set to 0Ω in measuring the IV characteristics. The results are shown in FIG. The open circuit voltage VS was about 1.3V. Therefore, the sample battery had the structure shown in FIG. It had a structure in which platinum plating was laminated in this order. However, the electrode structure does not actually have a clean electrode structure as shown in FIG.

A start voltage of -1.0 V to +1.0 V is applied to the open circuit voltage VS of 1.3 V (the actual voltage range is 0.3 V to 2.3 V), and the speed is 0.56 V / s. (direction along arrow X23). A current on the positive side of the sample battery produced corresponds to charging, and a current on the negative side corresponds to discharging. When the voltage was increased from the start, the current abruptly increased at about 1.8V and reached the peak current (about 0.07A) at about 2.1V. After that, the current dropped sharply to 0.007A at 2.3V. When the voltage scan was reversed at 2.3 V and the voltage was lowered, it became 0 A at 1.3 V, and the current increased to the negative side. At around 1.2V, the current increase on the minus side gradually increased, and reached a peak current (about -0.07A) at around 0.6V. When the voltage was further lowered, the current on the negative side abruptly decreased to -0.002A at 0.3V. When the voltage scan was reversed at 0.3V and the voltage was increased, the current on the minus side decreased to 0A at 1.3V. The scan ended here.

(Battery characteristics)
Next, FIG. 24 shows the relationship between the voltage and the amount of electricity supplied. When charging, the voltage started from 1.3V and became about 1.8V with a small amount of electricity. As the amount of electricity was increased, the voltage gradually increased up to 44.0 mAs. At around 45.0 mAs, the voltage increased significantly. At this point, it was determined that the battery was fully charged, and charging was terminated. The charge amount of electricity was 45.4 mAs.

During discharge, the circuit voltage started at 1.3 V, and the voltage reached about 1.0 V with a small amount of electricity. As the amount of electricity was increased, the voltage decreased up to 44.0 mAs, and the voltage decrease increased at around 45.0 mAs. The amount of discharged electricity was 45.0 mAs.

It can be said that the sample battery produced here is a secondary battery because the charge characteristics and the discharge characteristics were obtained, and the discharged quantity of electricity was almost equal to the charged quantity of electricity.

The present invention is not limited to the above-described embodiments, but can be modified in various ways within the scope of the claims, and can be obtained by appropriately combining technical means disclosed in different embodiments. is also included in the technical scope of the present invention.

REFERENCE SIGNS LIST 1 metal aluminum substrate 2 aluminum oxide film 11 negative electrode material 12 positive electrode material 13 separator

Claims (10)

a positive electrode material which is a p-type semiconductor made of oxygen-excessive aluminum oxide containing excess oxygen and having a conductive level capable of storing and releasing holes appearing in the bandgap due to excess oxygen;
A semiconductor battery comprising: a negative electrode material that is an n-type semiconductor made of oxygen-deficient aluminum oxide that lacks oxygen and has a conductive level that appears in a bandgap due to oxygen deficiency and is capable of storing and releasing electrons. . 2. The semiconductor battery of claim 1, further comprising a separator disposed between said positive electrode material and said negative electrode material. 3. The semiconductor cell according to claim 1, wherein said oxygen-excess aluminum oxide and said oxygen-deficient aluminum oxide are amorphous aluminum oxide or amorphous aluminum oxide containing polycrystals. 4. The method according to any one of claims 1 to 3, wherein the p-type semiconductor has a hole concentration of 10 ²² cm ⁻³ or more, and the n-type semiconductor has an electron concentration of 10 ²² cm ⁻³ or more. semiconductor battery. 5. The semiconductor battery according to any one of claims 1 to 4, further comprising a positive electrode current collector or a negative electrode current collector made of one of aluminum, an aluminum alloy, platinum and carbon. A positive electrode material for a semiconductor battery,
A positive electrode material comprising a p-type semiconductor composed of oxygen-excessive aluminum oxide containing an excess amount of oxygen and having a conductive level capable of accumulating and releasing holes appearing in a bandgap due to excess oxygen. A negative electrode material for a semiconductor battery,
A negative electrode material comprising an oxygen-deficient aluminum oxide that is oxygen-deficient and an n-type semiconductor having a conductive level capable of storing and releasing electrons that appears in a bandgap due to oxygen deficiency. A metal aluminum substrate is brought into contact with one surface of the aluminum oxide film, and a probe is brought into contact with the other surface of the aluminum oxide film, and between the metal aluminum substrate as an anode and the probe as a cathode, the aluminum oxide applying a voltage that causes dielectric breakdown of the film to melt the aluminum oxide film;
During the melting, molten salt electrolysis is generated in the aluminum oxide film, so that a negative electrode material, which is an n-type semiconductor, is formed on the metal aluminum substrate side of the aluminum oxide film and on the probe side of the aluminum oxide film. 1. A method of manufacturing a semiconductor battery, comprising: preparing positive electrode materials each of which is a p-type semiconductor; and bonding the negative electrode material and the positive electrode material. A metal aluminum substrate is brought into contact with one surface of the aluminum oxide film, and a probe is brought into contact with the other surface of the aluminum oxide film, and between the metal aluminum substrate as an anode and the probe as a cathode, the aluminum oxide applying a voltage that causes dielectric breakdown of the film to melt the aluminum oxide film;
During the melting, molten salt electrolysis is generated in the aluminum oxide film, so that a positive electrode material, which is a p-type semiconductor, is placed on the metal aluminum substrate side of the aluminum oxide film on the probe side of the aluminum oxide film. 1. A method of manufacturing a semiconductor battery, comprising: preparing negative electrode materials each of which is an n-type semiconductor; and bonding the negative electrode material and the positive electrode material. A separator composed of a stoichiometric aluminum oxide film is formed between the negative electrode material and the positive electrode material by adjusting the amount of electricity passed between the metal aluminum substrate and the probe during the melting. 10. The method of manufacturing a semiconductor battery according to claim 8 or 9, wherein the semiconductor battery is manufactured.

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