Power storage device

Abstract

A power storage device 1 comprises: a first electrode 10 that functions as a p-type semiconductor; a second electrode 20 that functions as an n-type semiconductor; and an oxygen vacancy region 30 that is disposed between the first electrode 10 and the second electrode 20. The first electrode 10 preferably contains manganese oxide. In addition, the second electrode 20 preferably contains tin oxide. The oxygen vacancy region 30 also preferably contains zirconium oxide stabilized by yttrium oxide, cerium oxide, calcium oxide, magnesium oxide, or scandium oxide.

Description

Energy storage devices

[0001] The present invention relates to an electricity storage device.

[0002] With the widespread use of various electronic devices such as mobile phones, laptops, and digital cameras, research and development of various energy storage devices as power sources for these electronic devices is actively underway. A representative example of such an energy storage device is a lithium-ion secondary battery. A lithium-ion secondary battery generally comprises a positive electrode using lithium cobalt oxide or the like as an active material, a negative electrode using carbon or the like as an active material, and a separator separating the two electrodes, with the space between the electrodes filled with a nonaqueous electrolyte. While conventional lithium-ion secondary batteries have a relatively high capacity, they have issues with high-speed charging and discharging. Therefore, various energy storage devices have been proposed as alternatives to lithium-ion secondary batteries.

[0003] For example, in order to achieve high capacity and high input / output performance, a secondary battery has been proposed that includes a first electrode that functions as a p-type semiconductor, a second electrode that functions as an n-type semiconductor, and a solid electrolyte provided between the first electrode and the second electrode (see Patent Document 1).

[0004] Japanese Patent Application Laid-Open No. 2021-157882

[0005] However, as electronic devices become smaller and more powerful, there is a demand for small-sized, high-capacity, and high-speed charge / discharge storage devices as their power sources.

[0006] Therefore, an object of the present invention is to provide an electricity storage device that can be miniaturized, has a high capacity, and is excellent in high-speed charge / discharge characteristics.

[0007] The present invention provides an electricity storage device comprising: a first electrode including a p-type semiconductor; a second electrode including an n-type semiconductor; and an oxygen vacancy portion disposed between the first electrode and the second electrode.

[0008] According to the present invention, an electricity storage device is provided which can be miniaturized, has a high capacity, and is excellent in high-speed charge / discharge characteristics.

[0009] FIG. 1 is a cross-sectional view schematically showing the structure of an electricity storage device of the present invention. FIG. 2 is a cross-sectional view schematically showing the structure of another embodiment of an electricity storage device of the present invention. FIG. 3 is a cross-sectional view schematically showing the structure of yet another embodiment of an electricity storage device of the present invention. FIG. 4 is a cross-sectional view schematically showing the structure of yet another embodiment of an electricity storage device of the present invention. FIG. 5 is a cross-sectional view schematically showing the structure of yet another embodiment of an electricity storage device of the present invention. FIG. 6 is a cross-sectional view schematically showing the structure of yet another embodiment of an electricity storage device prepared in Example 7.

[0010] The present invention will be described below based on preferred embodiments with reference to the drawings. [Electricity Storage Device] As mentioned above, a lithium-ion secondary battery is a representative example of an electricity storage device according to the present invention. Other electricity storage devices include, but are not limited to, lead-acid batteries, nickel-metal hydride batteries, supercapacitors (electric double-layer capacitors), and all-solid-state batteries. The electricity storage device according to the present invention has charge / discharge characteristics similar to those of supercapacitors. FIG. 1 is a schematic diagram showing one embodiment of an electricity storage device according to the present invention. The electricity storage device shown in the figure includes a first electrode 10, a second electrode 20, and an oxygen vacancy 30 disposed between these electrodes. The electricity storage device 1 further includes a first current collector 11 and a second current collector 22. The first current collector 11 and the second current collector 22 may each be independently made of a metal such as aluminum or copper. The first current collector 11 is disposed on the side of the first electrode 10 that does not face the oxygen vacancy 30. On the other hand, the second current collector 22 is disposed on one of the two surfaces of the second electrode 20 that does not face the oxygen vacancy portion 30 .

[0011] The first electrode 10 includes a p-type semiconductor and thereby functions as a p-type semiconductor. On the other hand, the second electrode 20 includes an n-type semiconductor and thereby functions as an n-type semiconductor. The first electrode 10 functions as a positive electrode. The second electrode 20 functions as a negative electrode. How the first electrode 10 and the second electrode 20 function will be described later.

[0012] In the electricity storage device 1 of the embodiment shown in FIG. 1 , the first electrode 10 and the oxygen vacancy 30 are in direct contact with each other. In other words, no other layer is interposed between them. However, in order to improve various performances of the electricity storage device 1, one or more other layers may be interposed between the first electrode 10 and the oxygen vacancy 30. In the electricity storage device 1 of the embodiment shown in FIG. 1 , the second electrode 20 and the oxygen vacancy 30 are in direct contact with each other. In other words, no other layer is interposed between them. However, in order to improve various performances of the electricity storage device 1, one or more other layers may be interposed between the second electrode 20 and the oxygen vacancy 30.

[0013] The electricity storage device 1 of this embodiment, which includes a first electrode 10 including a p-type semiconductor, a second electrode 20 including an n-type semiconductor, and an oxygen vacancy 30, differs from conventional lithium-ion secondary batteries in that charging and discharging are achieved by the movement of holes and electrons rather than the movement of ions. This will be described in detail below. First, during charging, a high-potential terminal of an external power supply (not shown) is electrically connected to the first electrode 10. Furthermore, a low-potential terminal is electrically connected to the second electrode 20. When a voltage is applied between the two electrodes 10 and 20, holes present in the first electrode 10 migrate to the surface facing the oxygen vacancy 30 and its vicinity. At the same time, electrons present in the second electrode 20 migrate toward the surface facing the oxygen vacancy 30. Therefore, both charges are accumulated near both surfaces of the oxygen vacancy 30, forming an electricity storage device. The oxygen vacancies in the oxygen vacancy 30 are charged divalently and are electrically coupled with electrons supplied from the second electrode 20, resulting in continuous accumulation of electrons.

[0014] On the other hand, during discharge, holes present in the first electrode 10 move toward the first current collector 11. At the same time, electrons that had been bonded to oxygen vacancies in the oxygen vacancy portion 30 are released, and the electrons present in the second electrode 20 move toward the second current collector 22 and are further released into an external circuit (not shown), causing a current to flow in the external circuit.

[0015] The advantages of the electricity storage device 1 of this embodiment, which can be charged and discharged based on the above-described principle, are as follows. Holes and electrons are smaller and lighter than ions and therefore have high mobility. Therefore, the electricity storage device of the present invention operates by the movement of holes, which is faster than the movement of ions. As a result, the electricity storage device 1 of this embodiment has high-speed charging performance. Furthermore, since the electricity storage device 1 of this embodiment does not involve chemical reactions during charging and discharging, it has a long life, high capacity, high output, and high safety.

[0016] [First Electrode] As described above, the first electrode 10 is composed of a p-type semiconductor material, and thereby functions as a p-type semiconductor. There are no particular limitations on the type of p-type semiconductor material used. Any p-type semiconductor material known to date can be used. Examples of p-type semiconductor materials include the following: (p-1) Impurity semiconductor materials in which an intrinsic semiconductor material such as silicon, germanium, or selenium is doped with a trivalent element such as boron, aluminum, or gallium. (p-2) Compound semiconductor materials composed of two or more elements. (p-3) Oxide semiconductor materials. These p-type semiconductor materials can be used alone or in combination of two or more.

[0017] Specific examples of p-type semiconductor materials include, but are not limited to, copper oxide, cuprous oxide, iron oxide, manganese(IV) oxide, nickel oxide, cobalt(II) oxide, tricobalt tetroxide, and rhodium oxide. When manganese oxide is used as the p-type semiconductor material, the manganese oxide may be doped with an alkali metal. Examples of alkali metals include lithium. Manganese oxide has low solubility, making it difficult to pattern it by wet etching. Therefore, when forming the first electrode 10 made of manganese oxide by sputtering and patterning it without using a metal mask, it is preferable to perform lithography and dry etching after film formation. Manganese oxide has a large work function as a p-type semiconductor, which ensures a large hole generation rate. As a result, using manganese oxide for the first electrode 10 allows for a high-capacity electricity storage device 1 to be obtained.

[0018] The first electrode 10 can be formed by various thin film formation methods. Examples of various thin film formation methods include, but are not limited to, sputtering and chemical vapor deposition. Alternatively, instead of a thin film formation method, the first electrode 10 can be formed by applying a slurry containing particles of a p-type semiconductor material. Furthermore, the first electrode 10 can also be formed by compression molding particles of a p-type semiconductor material.

[0019] [Second Electrode] As described above, the second electrode 20 is composed of an n-type semiconductor material, and thereby functions as an n-type semiconductor. Because the second electrode 20 functions as an n-type semiconductor, it can absorb and release ions, holes, and electrons generated in the first electrode 10, which functions as a p-type semiconductor. The type of n-type semiconductor material used is not particularly limited. Any n-type semiconductor material known to date can be used. Examples of n-type semiconductor materials include the following: (n-1) Impurity semiconductor materials in which an intrinsic semiconductor material such as silicon, germanium, or selenium is doped with a pentavalent element such as phosphorus, arsenic, or antimony; (n-2) Compound semiconductor materials composed of two or more elements; and (n-3) Oxide semiconductor materials. These n-type semiconductor materials can be used alone or in combination of two or more.

[0020] Specific examples of n-type semiconductor materials include graphene, various natural graphites, artificial graphite, zinc oxide, tin (IV) oxide, and titanium alloys. These materials can be used alone or in combination. In particular, when graphene is used as the n-type semiconductor material, the volume in which charges can be stored in the second electrode 20 during charging increases, and charges can be arranged in an orderly manner in the direction perpendicular to the electric field. As a result, charges are less likely to leak, and the amount of charge storage increases. This has the advantage of further increasing the storage capacity.

[0021] When tin oxide is used as the n-type semiconductor material, the tin oxide may be doped with a pentavalent metal element. Examples of such elements include antimony, bismuth, and arsenic. Doping of tin oxide with antimony or bismuth is performed, for example, using a high-shear disperser. Since tin oxide, which functions as an n-type semiconductor, is less likely to generate heat, an electricity storage device 1 having tin oxide in the second electrode 20 has the advantage of being less likely to generate heat even when an internal short circuit occurs in the electricity storage device 1. This improves the safety and lifespan of the electricity storage device 1. In particular, when the second electrode 20 contains tin oxide, an electron accumulation layer can be provided in the second electrode 20.

[0022] The n-type semiconductor material may be doped with metal elements other than those mentioned above, such as alkali metal elements (lithium, sodium, potassium, etc.) and transition metal elements such as zinc, titanium, and copper.

[0023] The second electrode 20 can be formed by various thin film formation methods. Examples of various thin film formation methods include, but are not limited to, sputtering and chemical vapor deposition. Alternatively, instead of a thin film formation method, the first electrode 10 can be formed by applying a slurry containing particles of an n-type semiconductor material. Furthermore, the first electrode 10 can also be formed by compression molding particles of an n-type semiconductor material.

[0024] [Oxygen Vacancy Portion] The oxygen vacancy portion 30 is made of a material having an oxygen vacancy. The material making up the oxygen vacancy portion 30 is generally a metal oxide, and the atomic ratio of oxygen element to metal element in the oxide is smaller than the stoichiometric ratio. This enables the oxygen vacancy portion 30 to exhibit oxide ion conductivity or proton conductivity. In this embodiment, the oxygen vacancy portion 30 may be made of a single layer containing a single material having an oxygen vacancy, or may be made of two or more layers each containing a different material.

[0025] The presence of oxygen vacancies 30 between the first electrode 10 and the second electrode 20 enables the transport of holes between the first electrode 10, which functions as a p-type semiconductor, and the second electrode 20, which functions as an n-type semiconductor. At the same time, physical contact between the first electrode 10 and the second electrode 20 is prevented. In contrast, if an insulator such as silica or an organic polymer such as epoxy resin is used as the oxygen vacancies 30, electrons in the second electrode 20, which functions as an n-type semiconductor, cannot move to the insulator or organic polymer, and the device does not function as an electricity storage device. Furthermore, the inventors have confirmed that if an acrylic resin having radicals is used as the oxygen vacancies 30, initial characteristics can be obtained, but the electricity storage device deteriorates due to oxidation-reduction reactions, resulting in a short lifespan.

[0026] The oxygen vacancy portion 30 is preferably composed of, for example, zirconium oxide, cerium oxide, lanthanum gallium perovskite oxide, bismuth oxide, and thorium oxide, from the viewpoint of improving the battery performance of the power storage device 1. The inventors have confirmed that zirconium oxide in particular can be used even at a high potential of 10 V. Zirconium oxide is also economically advantageous compared to other materials having oxygen vacancies. When the oxygen vacancy portion 30 contains zirconium oxide, various oxides may be doped into zirconium oxide to stabilize the crystal structure of zirconium oxide and adjust the amount of oxygen vacancy. Examples of oxides that can be doped into zirconium oxide include at least one selected from yttrium oxide, cerium oxide, calcium oxide, magnesium oxide, and scandium oxide. The amount of the various oxides doped into zirconium oxide can be set to, for example, 0.0001% by mass or more and 50% by mass or less, preferably 1% by mass or more and 25% by mass or less, and more preferably 5% by mass or more and 15% by mass or less, based on the stabilized zirconium oxide, from the viewpoint of stabilizing the zirconium oxide crystals and adjusting the amount of oxygen deficiency.

[0027] The oxygen vacancies 30 can be formed by various thin film formation methods, such as sputtering or chemical vapor deposition. Alternatively, the oxygen vacancies 30 can be formed by applying a slurry containing particles of a material having oxygen vacancies or by compression molding the particles of a material having oxygen vacancies. Alternatively, a fiber sheet such as a nonwoven fabric, woven fabric, knitted fabric, or paper can be used as a support, and the oxygen vacancies 30 can be formed on at least one surface of the support by the various methods described above.

[0028] As described above, the first electrode 10, the second electrode 20, and the oxygen vacancy 30 constituting the energy storage device 1 according to this embodiment can be formed by a thin-film formation method, such as sputtering or vapor deposition. Manufacturing the energy storage device 1 by such a method facilitates the thinning and miniaturization of the energy storage device. For example, a small chip-type energy storage device measuring several millimeters square can be obtained. The small-sized chip-type energy storage device can be directly mounted on the electronic substrate of an electronic device. Furthermore, the chip-type energy storage device can be safely installed in a narrow space in a small electronic device such as a cardiac pacemaker. Furthermore, since the energy storage device does not involve a chemical reaction during operation, the battery does not expand or contract as occurs in conventional lithium-ion secondary batteries, and the device can maintain its small chip-like shape. In contrast, conventional lithium-ion secondary batteries are mostly formed by kneading an active material with a solvent and then applying the resulting slurry, which limits the thinning and miniaturization of the electrodes. This also limits the miniaturization of the battery.

[0029] The power storage device 1 of this embodiment can be disposed on, for example, an electronic circuit board of an electronic device to function as a power source or auxiliary power source for the electronic device. For example, the power storage device 1 can be mounted on an electronic circuit board of a pacemaker to function as the pacemaker's main power source. The power storage device 1 is highly safe because it does not undergo chemical reactions during charging and discharging. Therefore, the power storage device 1 is suitable as a pacemaker's main power source. Furthermore, the power storage device 1 is not a non-rechargeable primary battery used in conventional pacemakers, and is therefore rechargeable, making it suitable as a pacemaker's main power source. In addition, the power storage device 1 can be mounted on an electronic circuit board of a personal computer to function as an auxiliary power source. In this case, it is possible to retain the contents of the volatile memory and mitigate shock to electronic components when the power supply from the main power source is interrupted due to a power outage or the like. Furthermore, even when the main power source is off, the power storage device 1 can supply power to the volatile memory and retain the stored contents.

[0030] Another embodiment of the energy storage device of the present invention is shown in FIG. 2 . As shown in the figure, the energy storage device 1 of this embodiment can be placed on an electronic board while housed in a housing 40. The housing 40 can be formed, for example, from a conductive material (such as copper). The housing 40 can have a main body 41 and a lid 42. The main body 41 and the lid 42 can be formed from the same or different conductive materials. The main body 41 has an opening 41 a and an internal housing space S for the energy storage device 1. The housing space S is in communication with the outside of the main body 41 through the opening 41 a. The lid 42 has a shape that can close the entire opening 41 a of the main body 41. It is preferable that the lid 42 and the main body 41 are not electrically connected when the lid 42 closes the opening 41 a. For this purpose, it is preferable to dispose an electrically insulating O-ring 43 on the periphery 41 b of the opening 41 a , and to electrically insulate the lid portion 42 from the main body portion 41 by this O-ring 43 .

[0031] When the electricity storage device 1 is placed in the housing 40, the first electrode 10 can be electrically connected to the lid portion 42 via a current-carrying member 44, as shown in FIG. 2 . Examples of the current-carrying member 44 that can be used include a wire, a conductive paste, and a lead wire. Meanwhile, the second electrode 20 can be electrically connected to any position on the main body portion 41, for example, the bottom surface portion 41 c. The main body portion 41 and the lid portion 42 in the housing 40 are electrically connected to the circuit of the electronic board, so that the electricity storage device 1 functions as a power source or auxiliary power source for the electronic device. By housing the electricity storage device 1 in the housing 40, deterioration of the electricity storage device 1 due to heat generation by the electronic device and leakage of electricity when the electronic device is submerged in water are effectively prevented.

[0032] The second electrode 20 and the bottom surface 41c of the main body 41 can be electrically connected by, for example, a method using a metal mask. When a metal mask is used, the second electrode 20, the oxygen vacancy portion 30, and the first electrode 10 may be laminated in this order on the bottom surface 41c of the main body 41 using various thin film formation methods such as sputtering or CVD to manufacture the electricity storage device 1. As a result, the bottom surface 41c of the main body 41 and the second electrode 20 are directly and electrically connected. As an alternative method, instead of using a metal mask, the electricity storage device 1 may be manufactured by a method of performing lithography and etching after film formation.

[0033] In the embodiment shown in FIG. 2 , the first electrode 10 is electrically connected to the lid portion 42 of the housing 40. Alternatively, the first electrode 10 may be electrically connected to the side wall portion 41 d of the main body portion 41. In this case, it is preferable to interpose an electrically insulating O-ring between the bottom surface 41 c and the side wall portion 41 d of the main body portion 41 to electrically insulate the bottom surface 41 c from the side wall portion 41 d. This prevents a short circuit from occurring between the first electrode 10 and the second electrode 20. When the first electrode 10 is connected to the side wall portion 41 d of the main body portion 41, it is not necessary to place an O-ring in the opening 41 a of the main body portion 41 to electrically insulate the main body portion 41 from the lid portion 42.

[0034] A housing made of an electrically insulating material such as silica may be used instead of using a conductive housing 40. In this case, through-holes (not shown) may be provided at any positions in the housing 40, and current-carrying members (not shown) electrically connected to the first electrode 10 and the second electrode 20 may be led out of the housing 40 through the through-holes.

[0035] Alternative Embodiment 2 When the electricity storage device 1 is housed in a housing, the embodiment shown in Figure 3 can be employed instead of Figure 2. In the embodiment shown in Figure 3, the electricity storage device 1, which is formed by stacking the second electrode 20, the oxygen vacancy portion 30, and the first electrode 10 in this order, is formed on a support member 45 made of an insulating material (e.g., silica) to produce a unit 46, and the unit 46 is housed in the housing 40. A through-hole 45a is formed in the support member 45 of the unit 46. A current-carrying member 44 is disposed in the through-hole 45a. The current-carrying member 44 electrically connects the second electrode 20 and the bottom surface portion 41c of the main body portion 41.

[0036] 3, the support member 45 made of an insulating material may be replaced by a support member 45 made of a conductive material. In this case, the through-holes 45a and the conductive members 44 are not required.

[0037] Another embodiment of the electricity storage device of the present invention is shown in FIG. 4. The embodiment shown in the figure has a plurality of electricity storage device units 50, each including a first electrode 10, an oxygen vacancy 30, and a second electrode 20. The figure shows two sets of units 50: a first unit 50a and a second unit 50b. The multiple units 50 are stacked so that the first electrode 10 of the first unit 50a and the second electrode 20 of the second unit 50b are in direct contact with each other. As a result, the electricity storage device 1 of this embodiment has two sets of units 50a and 50b connected in series. Therefore, the electricity storage device 1 of this embodiment outputs twice the voltage as the electricity storage devices 1 described above.

[0038] 4 , a second current collector 12 is disposed on the outer surface of the second electrode 20 in the first unit 50a. Meanwhile, a first current collector 11 is disposed on the outer surface of the first electrode 10 in the second unit 50b. By connecting a load between the first current collector 11 and the second current collector 12, it is possible to extract current to the outside.

[0039] It is preferable that no current collector is disposed between the first electrode 10 of the first unit 50a and the second electrode 20 of the second unit 50b. In other words, it is preferable that no current collector is disposed between the two units 50a and 50b. If a current collector is disposed between the first electrode 10 of the first unit 50a and the second electrode 20 of the second unit 50b, the first unit 50a and the second unit 50b will not be diode-connected, which may cause current leakage.

[0040] As shown in FIG. 4 , in the first unit 50a, the oxygen vacancy 30 located between the first electrode 10 and the second electrode 20 extends laterally from the periphery of each of these electrodes 10 and 20 and is arranged so as to cover the side surfaces of the first electrode 10 and the second electrode 20. Therefore, in the first unit 50a, both the first electrode 10 and the second electrode 20 are entirely covered by the oxygen vacancy 30. On the other hand, in the second unit 50b, the oxygen vacancy 30 located between the first electrode 10 and the second electrode 20 extends laterally from the periphery of each of these electrodes 10 and 20 and is arranged so as to cover the side surface of the second electrode 20. The side surface of the first electrode 10 in the second unit 50b is exposed. Therefore, in the second unit 50b, only the second electrode 20 is entirely covered by the oxygen vacancy 30. The oxygen vacancy 30 in the first unit 50a and the oxygen vacancy 30 in the second unit 50b are integrated with each other. By arranging the oxygen vacancy 30 in this manner, it is possible to effectively prevent the first electrode 10 and the second electrode 20 from contacting each other within one unit. Preventing the first electrode 10 and the second electrode 20 from contacting each other within one unit has the advantage that charges can be accumulated as one independent unit.

[0041] Alternative Embodiment 4 In the embodiment shown in FIG. 5 , the first electrode 10 in the first unit 50a and the first electrode 10 in the second unit 50b are arranged so that they face each other, with a first current collector 11 interposed between the two electrodes 10. Therefore, the two first electrodes 10 are electrically connected by the first current collector 11. In this state, as shown in the figure, the second electrode 20 in the first unit 50a and the second electrode 20 in the second unit 50b face outward. The two second electrodes 20 are electrically connected by a single second current collector 22. Therefore, the first unit 50a and the second unit 50b are connected in parallel. By connecting a load between the first current collector 11 and the second current collector 22, it is possible to extract twice the current capacity externally.

[0042] In the first unit 50a, the oxygen vacancy 30 extends laterally from the peripheries of the first electrode 10 and the second electrode 20 and is disposed so as to cover the side surfaces of the first electrode 10 and the second electrode 20. The extended oxygen vacancy 30 also covers the side surfaces of the first current collector 11. On the other hand, in the second unit 50b, the oxygen vacancy 30 extends laterally from the peripheries of the first electrode 10 and the second electrode 20 and is disposed so as to cover the side surfaces of the first electrode 10 and the second electrode 20. Therefore, in the first unit 50a, both the first electrode 10 and the second electrode 20 are entirely covered by the oxygen vacancy 30. Similarly, in the second unit 50b, both the first electrode 10 and the second electrode 20 are entirely covered by the oxygen vacancy 30. The oxygen vacancy 30 of the first unit 50a and the oxygen vacancy 30 of the second unit 50b are integrated with each other. By arranging the oxygen vacancy 30 in this manner, it is possible to effectively prevent the first electrode 10 and the second electrode 20 from coming into contact with each other within one unit.

[0043] Note that the explanations for the embodiment shown in Figures 1 to 3 apply as appropriate to points not specifically explained in the embodiment shown in Figures 4 and 5. In Figures 4 and 5, the same members as those in Figures 1 to 3 are denoted by the same reference numerals.

[0044] While the present invention has been described above based on preferred embodiments thereof, the present invention is not limited to these embodiments. For example, the power storage device shown in Figures 4 and 5 may be housed in the housing 40 shown in Figure 2 or 3.

[0045] The present invention will be described in more detail below with reference to examples. However, the scope of the present invention is not limited to such examples. Unless otherwise specified, "%" and "parts" mean "% by mass" and "parts by mass", respectively.

[0046] Example 1 Zirconium oxide powder manufactured by Tosoh Corporation and PVDF #1320 manufactured by Kureha Corporation (a solution containing 12 parts solids in N-methylpyrrolidone (NMP)) were mixed at a mass ratio of 94:6. The mixture was dispersed to obtain a slurry. This slurry was impregnated into 4 μm-thick Japanese paper for 5 minutes. The Japanese paper impregnated with the slurry was vacuum-dried at 120°C for 12 hours. In this manner, oxygen vacancies 30 were obtained. A paint containing antimony-doped n-type tin oxide powder (manufactured by Mitsui Mining & Smelting Co., Ltd.) was applied to one side of the oxygen vacancies 30 to form a second electrode 20. The n-type tin oxide paint was prepared as follows: MAC-350HC (CMC powder) manufactured by Nippon Paper Industries Co., Ltd. was added to pure water to a concentration of 1.4% and stirred. The n-type tin oxide powder was then added to the mixture. Further, a binder BM-451B manufactured by Zeon Corporation was added and stirred. The mass ratio of the n-type tin oxide powder, the BM451B binder solid content, and the CMC solid content was 92:4:4. Next, a paint containing manganese oxide was applied to the other surface of the oxygen vacancy portion 30 to form a first electrode 10. Two units 50 thus obtained were connected in series to form a stacked electricity storage device. The film volume ratio of n-type tin oxide:zirconium oxide:manganese oxide was 6:7:17. The thickness of the first electrode was 18 μm, the thickness of the oxygen vacancy portion was 21 μm, and the thickness of the second electrode was 50 μm. This electricity storage device was subjected to a charge / discharge evaluation. The results are shown in Table 1 below.

[0047]

[0048] As is clear from the results shown in Table 1, the electricity storage device of Example 1 can be charged at a high voltage, i.e., can be rapidly charged, by stacking units 50 each consisting of a first electrode 10, an oxygen vacancy 30, and a second electrode 20 in series. Furthermore, connecting the units 50 in parallel is expected to enable high-rate discharge. Therefore, in Example 2 described below, we consider the possibility of increasing output when multiple units 50 are connected in parallel.

[0049] [Example 2] Four units 50 obtained in Example 1 were used, and units 50a to 50d were connected in parallel as shown in Fig. 6. A stacked electricity storage device was obtained in the same manner as in Example 1 except for this. This electricity storage device was evaluated in the same manner as in Example 1. The results are shown in Table 2 below.

[0050]

[0051] As shown in Table 2, it can be seen that the energy storage device of Example 2 can be charged in a short time even when rapidly charged. Furthermore, no heat generation from this energy storage device was observed during rapid charging. Since the resistance |Z| of the energy storage device is expressed by the following formula (1), when the energy storage device has the structure of this example, the resistance decreases as the number of parallel connections increases. Therefore, it is advantageous because the performance of the energy storage device can be obtained to be greater than the sum of the capacities.

[0052]

[0053] [AC Impedance Measurement for the Energy Storage Devices of Examples 1 and 2] AC impedance measurements were performed on the energy storage devices of Examples 1 and 2. The AC impedance measurements were performed at room temperature of 25°C and under OCV conditions. The frequency range was set to 10 mHz to 10 kHz. The measurement device used was a BCS810 (manufactured by Biologic). The Nyquist plot and its results were fitted using equivalent circuit analysis, and the sum of the resistances at each measurement point calculated from the results was taken as resistance |Z|. The results are shown in Table 3 below.

[0054]

[0055] As is clear from the results shown in Table 3, it was confirmed that the resistance value |Z| decreases as the number of units connected in parallel increases.

[0056] Examples 3 to 18 Manganese oxide was used as the material for the first electrode. Zirconium oxide was used as the material for the oxygen vacancies. N-type tin oxide was used as the material for the second electrode. The amounts of these materials were as shown in Table 4 below. Zirconium oxide stabilized with the dopants shown in the table was used. The amounts of dopants shown in the table are values ​​relative to the stabilized zirconium oxide. Each substance was weighed, filled into a powder compaction cell manufactured by Iject, and then pressed under pressure to obtain an electricity storage device. The open-circuit voltage and resistance (before charging) of the obtained electricity storage device were measured. The results are shown in Table 4.

[0057]

Claims

1. An electricity storage device comprising: a first electrode including a p-type semiconductor; a second electrode including an n-type semiconductor; and an oxygen vacancy portion disposed between the first electrode and the second electrode.

2. The electricity storage device according to claim 1, wherein the oxygen vacancies contain zirconium oxide.

3. The electricity storage device according to claim 1 or 2, comprising a plurality of units each including a first electrode, the oxygen vacancy, and a second electrode, wherein the plurality of units are stacked such that the first electrode in one unit is in direct contact with the second electrode in another unit, or the first electrode in one unit is electrically connected to the first electrode in another unit, and the second electrode in one unit is electrically connected to the second electrode in another unit.

4. The electricity storage device according to claim 2, wherein the oxygen vacancies include zirconium oxide stabilized with yttrium oxide, cerium oxide, calcium oxide, magnesium oxide, or scandium oxide.

5. The electricity storage device according to claim 1 or 2, wherein the first electrode contains manganese oxide.

6. The electricity storage device according to claim 1 or 2, wherein the second electrode contains tin oxide.

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