Electric energy storage device

Abstract

The energy storage device 1 includes 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 portion 30 disposed between the first electrode 10 and the second electrode 20. It is preferable that the first electrode 10 contains manganese oxide. It is also preferable that the second electrode 20 contains tin oxide. It is also preferable that the oxygen vacancy portion 30 contains zirconium oxide stabilized with yttrium oxide, cerium oxide, calcium oxide, magnesium oxide, or scandium oxide.

Description

Technical Field

[0001] The present invention relates to a power storage device.

Background Art

[0002] With the spread of various electronic devices such as mobile phones, notebook computers, and digital cameras, research and development of various power storage devices have been actively carried out as power sources for these electronic devices. A typical example of such a power storage device is a lithium-ion secondary battery. A lithium-ion secondary battery generally includes a positive electrode using lithium cobaltate or the like as an active material, a negative electrode using carbon or the like as an active material, a separator separating the two electrodes, and the space between the two electrodes is filled with a non-aqueous electrolyte. Although conventional lithium-ion secondary batteries have a relatively high capacity, they have problems with high-speed charge and discharge. Therefore, various power storage devices alternative to lithium-ion secondary batteries have been proposed.

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

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, with the miniaturization and high performance of electronic devices, there is a demand for a power storage device that is small, has a high capacity, and has excellent high-speed charge and discharge characteristics as its power source.

[0006] Accordingly, an object of the present invention is to provide a power storage device that can be miniaturized, has a high capacity, and excellent fast charge and discharge characteristics.

Means for Solving the Problems

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

Effects of the Invention

[0008] According to the present invention, a power storage device that can be miniaturized, has a high capacity, and excellent fast charge and discharge characteristics is provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0010] Hereinafter, the present invention will be described with reference to the drawings based on its preferred embodiments. 〔Power Storage Device〕 As the power storage device according to the present invention, a lithium ion secondary battery is cited as a typical example as described above. Other power storage devices include, for example, lead storage batteries, nickel-metal hydride batteries, supercapacitors (electric double layer capacitors), and all-solid-state batteries, but are not limited thereto. The power storage device according to the present invention has charge and discharge characteristics similar to those of a supercapacitor. FIG. 1 is a schematic diagram showing an embodiment of the power storage device of the present invention. The power storage device shown in the figure includes a first electrode 10, a second electrode 20, and an oxygen vacancy portion 30 disposed between these electrodes. Furthermore, the power storage device 1 includes a first current collector 11 and a second current collector 22. The first current collector 11 and the second current collector 22 can each be independently composed of a metal such as aluminum or copper, for example. The first current collector 11 is disposed on the non-opposing surface side with respect to the oxygen vacancy portion 30 among the two surfaces of the first electrode 10. On the other hand, the second current collector 22 is disposed on the non-opposing surface side with respect to the oxygen vacancy portion 30 among the two surfaces of the second electrode 20.

[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 power storage device 1 of the embodiment shown in FIG. 1, the first electrode 10 and the oxygen vacancy portion 30 are in direct contact. In other words, no other layer is interposed therebetween. However, for the purpose of enhancing various performances of the power storage device 1, one or two or more other layers may be interposed between the first electrode 10 and the oxygen vacancy portion 30. In the power storage device 1 of the embodiment shown in FIG. 1, the second electrode 20 and the oxygen vacancy portion 30 are in direct contact. In other words, no other layer is interposed therebetween. However, for the purpose of enhancing various performances of the power storage device 1, one or two or more other layers may be interposed between the second electrode 20 and the oxygen vacancy portion 30.

[0013] The energy storage device 1 of the present embodiment including a p-type semiconductor first electrode 10, an n-type semiconductor second electrode 20, and an oxygen vacancy portion 30 achieves charge and discharge by the movement of holes and electrons, rather than the movement of ions, which is different from the conventional lithium ion secondary battery. This will be described in detail below. First, during charging, the high potential terminal of an external power source (not shown) is electrically connected to the first electrode 10. Further, the low potential terminal is electrically connected to the second electrode 20. By applying a voltage between both electrodes 10 and 20, the holes existing in the first electrode 10 move to the facing surface with the oxygen vacancy portion 30 and the vicinity thereof. At the same time, the electrons existing in the second electrode 20 move toward the facing surface with the oxygen vacancy portion 30. Therefore, both charges are respectively accumulated in the vicinity of both surfaces of the oxygen vacancy portion 30, and an energy storage device is formed. The oxygen vacancies in the oxygen vacancy portion 30 are charged to +2 valence, and are electrically combined with the electrons supplied from the second electrode 20 and continuously accumulated.

[0014] On the other hand, during discharging, the holes existing in the first electrode 10 move to the first current collector 11 side. At the same time, the electrons combined with the oxygen vacancies in the oxygen vacancy portion 30 are released, the electrons existing in the second electrode 20 move to the second current collector 22 side, and further, a current flows through an external circuit (not shown) by being released to the external circuit.

[0015] The advantages of the energy storage device 1 of the present embodiment capable of charge and discharge according to the above principle are as described below. That is, holes and electrons are smaller and lighter than ions, and thus have high mobility. Therefore, the energy storage device of the present invention operates by the movement of holes faster than the movement of ions. As a result, the energy storage device 1 of the present embodiment has high-speed charging performance. Further, the energy storage device 1 of the present embodiment has a long life because it does not involve a chemical reaction during charge and discharge, and also has 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. The type of p-type semiconductor material used is not particularly limited. Known p-type semiconductor materials can be used. For example, the following can be mentioned as p-type semiconductor materials. (p-1) An impurity semiconductor material obtained by doping an intrinsic semiconductor material such as silicon, germanium, or selenium with a trivalent element such as boron, aluminum, or gallium. (p-2) A compound semiconductor material composed of two or more elements. (p-3) An oxide semiconductor material. These p-type semiconductor materials can be used alone or in combination of two or more.

[0017] Specific examples of the p-type semiconductor material include, but are not limited to, copper oxide, cuprous oxide, iron oxide, manganese(IV) oxide, nickel oxide, cobalt(II) oxide, tricobalt tetraoxide, and rhodium oxide. When using manganese oxide as the p-type semiconductor material, it may be doped with an alkali metal. Examples of the alkali metal include lithium. Manganese oxide has low solubility and is difficult to pattern by wet etching. Therefore, when forming the first electrode 10 made of manganese oxide by sputtering and patterning without using a metal mask, it is preferable to perform lithography and dry etching after film formation. Since manganese oxide has a large work function as a p-type semiconductor, a large amount of holes can be ensured. As a result, by using manganese oxide for the first electrode 10, a power storage device 1 with a large capacitance can be obtained.

[0018] The first electrode 10 can be formed by various thin film formation methods. Examples of the various thin film formation methods include, but are not limited to, sputtering and chemical vapor deposition. Alternatively, instead of the thin film formation method, the first electrode 10 can also be formed by applying a slurry containing particles of the 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 configured to include an n-type semiconductor material and thereby functions as an n-type semiconductor. Since the second electrode 20 functions as an n-type semiconductor, it is possible to store and release ions, holes, and electrons generated in the first electrode 10 that functions as a p-type semiconductor. The type of n-type semiconductor material used is not particularly limited. Known n-type semiconductor materials can be used. For example, the following can be mentioned as n-type semiconductor materials. An impurity semiconductor material obtained by doping an intrinsic semiconductor material such as (n-1) silicon, germanium, or selenium with a pentavalent element such as phosphorus, arsenic, and antimony. (n-2) A compound semiconductor material composed of two or more elements. (n-3) An oxide semiconductor material. These n-type semiconductor materials can be used alone or in combination of two or more.

[0020] Specific examples of the n-type semiconductor material include graphene, various natural graphites, artificial graphites, zinc oxide, tin(IV) oxide, and titanium alloys. These substances can be used alone or in combination of two or more. Particularly when using graphene as the n-type semiconductor material, in the second electrode 20 during charging, the volume in which charges can be stored increases, and charges can be neatly arranged not only in the direction of the electric field but also in the direction perpendicular to it. As a result, the charges are less likely to leak and the charge storage amount increases. Thereby, there is an advantage that the capacity that can be stored further increases.

[0021] When using tin oxide as the n-type semiconductor material, the tin oxide may be doped with a pentavalent metal element. Such elements include, for example, antimony, bismuth, and arsenic. Doping of antimony or bismuth into tin oxide is performed, for example, using a high-shear force disperser. Tin oxide, which functions as an n-type semiconductor, is difficult to generate heat. Therefore, the power storage device 1 having tin oxide as the second electrode 20 has the advantage of being difficult to generate heat even when an internal short circuit occurs in the power storage device 1. Due to this, the safety and lifespan of the power storage device 1 are improved. In particular, by including tin oxide in the second electrode 20, an electron accumulation layer can be provided on the second electrode 20.

[0022] Other metal elements other than the above-described metal elements may be doped into the n-type semiconductor material. For example, alkali metal elements (such as lithium, sodium, and potassium), as well as transition metal elements such as zinc, titanium, and copper, may be doped.

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

[0024] 〔Oxygen Vacancy Portion〕 The oxygen vacancy portion 30 is composed of a material having oxygen deficiency. The material constituting the oxygen vacancy portion 30 is generally a metal oxide, and the atomic ratio of oxygen element to the metal element in the oxide is smaller than the stoichiometric ratio. As a result, the oxygen vacancy portion 30 can exhibit oxide ion conductivity or proton conductivity. In the present embodiment, the oxygen vacancy portion 30 may be composed of a single layer containing a material having oxygen deficiency, or may be composed of two or more layers each containing different materials.

[0025] By interposing an oxygen vacancy portion 30 between the first electrode 10 and the second electrode 20, hole transport becomes possible between the first electrode 10 functioning as a p-type semiconductor and the second electrode 20 functioning as an n-type semiconductor. At the same time, physical contact between the first electrode 10 and the second electrode 20 is prevented. On the other hand, when an insulator such as silica or an organic polymer such as epoxy resin is used as the oxygen vacancy portion 30, electrons in the second electrode 20 functioning as an n-type semiconductor cannot move to the insulator or the organic polymer, and the power storage device does not operate. Further, when an acrylic resin having radicals is used as the oxygen vacancy portion 30, the inventor has confirmed that although initial characteristics can be obtained, deterioration of the power storage device progresses due to redox reactions and the lifespan is short.

[0026] From the viewpoint of enhancing the battery performance of the power storage device 1, it is preferable that the oxygen vacancy portion 30 is composed of, for example, zirconium oxide, cerium oxide, lanthanum gallium perovskite oxide, bismuth oxide, and thorium oxide. In particular, the inventor has confirmed that zirconium oxide can be used even at a high potential of 10V. Also, zirconium oxide is economically advantageous compared to other materials having oxygen deficiencies. When the oxygen vacancy portion 30 contains zirconium oxide, various oxides may be doped into the zirconium oxide to stabilize the crystal structure of the zirconium oxide and adjust the amount of oxygen deficiency. 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 doping amount of the various oxides into zirconium oxide can be set, from the viewpoints of stabilizing the crystal of zirconium oxide and adjusting the amount of oxygen deficiency, to be, for example, 0.0001 mass% or more and 50 mass% or less with respect to stabilized zirconium oxide, preferably 1 mass% or more and 25 mass% or less, and more preferably 5 mass% or more and 15 mass% or less.

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

[0028] As described above, the first electrode 10, the second electrode 20, and the oxygen vacancy portion 30 constituting the power storage device 1 according to the present embodiment can be formed by a thin film formation method such as sputtering or vapor deposition. By manufacturing the power storage device 1 by such a method, it becomes possible to easily thin and miniaturize the power storage device. For example, a chip-shaped power storage device having a small size of several millimeters square can be obtained. A chip-shaped power storage device having a small size can be directly arranged on an electronic substrate of an electronic device. In addition, the chip-shaped power storage device can be safely installed in a narrow space in a small electronic device such as a heart pacemaker. Further, since the power storage device does not involve a chemical reaction during operation, the expansion and contraction of the battery, which occur in a conventional lithium ion secondary battery, do not occur, and it is possible to maintain a small chip shape. On the other hand, most conventional lithium ion secondary batteries are formed by kneading an active material and a solvent and applying the resulting slurry, so there is a limit to the thinning and miniaturization of the electrodes. As a result, there is also a limit to the miniaturization of the battery.

[0029] By arranging the power storage device 1 of the present embodiment on an electronic substrate of an electronic device, for example, it can function as a power source or an auxiliary power source of the electronic device. For example, the power storage device 1 can be mounted on the electronic substrate of a pacemaker and function as the main power source of the pacemaker. Since the power storage device 1 does not involve a chemical reaction during charge and discharge, it has high safety. Therefore, the power storage device 1 is suitable as the main power source of the pacemaker. Furthermore, the power storage device 1 is not a non-rechargeable primary battery used in conventional pacemakers, and is also suitable as the main power source of the pacemaker in that it is rechargeable. In addition, the power storage device 1 can also be mounted on the electronic substrate of a personal computer and function as an auxiliary power source. In this case, it becomes possible to retain the content of the volatile memory and mitigate the impact on electronic components when the power supply from the main power source is cut off due to a power outage or the like. Also, even when the main power source is off, power can be supplied from the power storage device 1 to the volatile memory to retain the stored content.

[0030] 〔Another Embodiment 1〕 FIG. 2 shows another embodiment of the power storage device of the present invention. As shown in the figure, the power storage device 1 of this embodiment can also be arranged on an electronic substrate in a state of being housed in a housing 40. The housing 40 can be formed of, for example, a conductive material (such as copper). The housing 40 can have a main body portion 41 and a lid portion 42. The main body portion 41 and the lid portion 42 can be formed of the same or different conductive materials. The main body portion 41 has an opening 41a and has an accommodation space S for the power storage device 1 inside. The accommodation space S communicates with the outside of the main body portion 41 through the opening 41a. The lid portion 42 has a shape that can close the entire area of the opening 41a of the main body portion 41. In a state where the lid portion 42 closes the opening 41a, it is preferable that the lid portion 42 and the main body portion 41 are not electrically conductive. For this purpose, it is preferable to arrange an electrically insulating O-ring 43 on the peripheral edge 41b of the opening 41a and electrically insulate the lid portion 42 and the main body portion 41 by this O-ring 43.

[0031] When the power storage device 1 is disposed within the housing 40, as shown in FIG. 2, the first electrode 10 can be electrically connected to the lid portion 42 via the current conducting member 44. As the current conducting member 44, for example, a wire, a conductive paste, a lead wire, or the like can be used. On the other hand, the second electrode 20 can be electrically connected to an arbitrary position of the main body portion 41, for example, the bottom surface portion 41c. When the main body portion 41 and the lid portion 42 of the housing 40 are electrically connected to the circuit of the electronic substrate, the power storage device 1 functions as a power source or an auxiliary power source of the electronic device. By housing the power storage device 1 within the housing 40, deterioration of the power storage device 1 due to heat generation of the electronic device and leakage of electricity when the electronic device is submerged can be effectively prevented.

[0032] The second electrode 20 and the bottom surface portion 41c of the main body portion 41 can be electrically connected by a method using, for example, a metal mask. When using a metal mask, various thin film forming methods such as sputtering or CVD can be used, and the power storage device 1 can be manufactured by laminating the second electrode 20, the oxygen vacancy portion 30, and the first electrode 10 in this order on the bottom surface portion 41c of the main body portion 41. As a result, the bottom surface portion 41c of the main body portion 41 and the second electrode 20 are directly electrically connected. As an alternative method, instead of using a metal mask, the power 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. Instead of such a connection, the first electrode 10 may be electrically connected to the side wall portion 41d of the main body portion 41. In this case, it is preferable to interpose an electrically insulating O-ring between the bottom surface portion 41c and the side wall portion 41d of the main body portion 41 to electrically insulate the bottom surface portion 41c and the side wall portion 41d. Thereby, a short circuit between the first electrode 10 and the second electrode 20 can be prevented from occurring. When connecting the first electrode 10 to the side wall portion 41d of the main body portion 41, it is not necessary to dispose an O-ring at the opening portion 41a of the main body portion 41 to electrically insulate the main body portion 41 and the lid portion 42.

[0034] Instead of using the conductive housing 40, a housing made of an electrically insulating material such as silica may be used. In this case, a through-hole (not shown) may be provided at an arbitrary location of the housing 40, and an energizing member (not shown) electrically connected to the first electrode 10 and the second electrode 20 respectively may be drawn out to the outside of the housing 40 through this through-hole.

[0035] 〔Another Embodiment 2〕 When the power storage device 1 is housed in a housing, the embodiment shown in FIG. 3 may be adopted instead of FIG. 2. In the embodiment shown in the figure, a power storage device 1 in which the second electrode 20, the oxygen vacancy portion 30, and the first electrode 10 are laminated in this order is formed on a support member 45 made of an insulating material (for example, silica or the like) to manufacture a unit 46, and the unit 46 is housed in a housing 40. A through-hole 45a is provided in the support member 45 in the unit 46. An energizing member 44 is disposed in the through-hole 45a. The energizing member 44 electrically connects the second electrode 20 and the bottom surface portion 41c of the main body portion 41.

[0036] In the embodiment shown in FIG. 3, a support member 45 made of a conductive material may be used instead of the support member 45 made of an insulating material. In this case, it is not necessary to provide the through-hole 45a and the energizing member 44.

[0037] 〔Another Embodiment 3〕 FIG. 4 shows another embodiment of the power storage device of the present invention. The embodiment shown in the figure has a plurality of units 50 of the power storage device including the first electrode 10, the oxygen vacancy portion 30, and the second electrode 20. The figure shows a state in which the unit 50 is composed of two sets, a first unit 50a and a second unit 50b. The plurality of units 50 are laminated such that the first electrode 10 in the first unit 50a is in direct contact with the second electrode 20 in the second unit 50b. As a result, the power storage device 1 of the present embodiment is in a state in which two sets of units 50a and 50b are connected in series. Therefore, the power storage device 1 of the present embodiment has a voltage output that is twice that of the power storage device 1 described so far.

[0038] As shown in FIG. 4, a second current collector 12 is disposed on the outer surface of the second electrode 20 in the first unit 50a. On the other hand, 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, current can be taken out to the outside.

[0039] It is preferable that no current collector is disposed between the first electrode 10 in the first unit 50a and the second electrode 20 in the second unit 50b. That is, 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 in the first unit 50a and the second electrode 20 in the second unit 50b, it will cause current leakage without the first unit 50a and the second unit 50b being diode-connected.

[0040] As shown in FIG. 4, in the first unit 50a, an oxygen vacancy portion 30 located between the first electrode 10 and the second electrode 20 extends laterally from the peripheral edges of these electrodes 10 and 20, respectively, and is arranged to cover the side surfaces of the first electrode 10 and the second electrode 20. Therefore, in the first unit 50a, the entire first electrode 10 and the second electrode 20 are covered by the oxygen vacancy portion 30. On the other hand, in the second unit 50b, an oxygen vacancy portion 30 located between the first electrode 10 and the second electrode 20 extends laterally from the peripheral edges of these electrodes 10 and 20, respectively, and is arranged 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 entire second electrode 20 is covered by the oxygen vacancy portion 30. The oxygen vacancy portion 30 of the first unit 50a and the oxygen vacancy portion 30 of the second unit 50b are integrated with each other. By arranging the oxygen vacancy portion 30 in this way, it is possible to effectively prevent the first electrode 10 and the second electrode 20 from contacting each other in one unit. By preventing the first electrode 10 and the second electrode 20 from contacting each other in one unit, there is an advantage that charges can be accumulated as one independent unit.

[0041] 〔Another 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 face each other, and the two units 50a and 50b are arranged such that the first current collector 11 is interposed between the two electrodes 10, 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, a current with twice the capacitance can be taken out to the outside.

[0042] In the first unit 50a, the oxygen vacancy portion 30 extends laterally from the peripheries of the first electrode 10 and the second electrode 20 and is arranged to cover the side surfaces of the first electrode 10 and the second electrode 20. The extended oxygen vacancy portion 30 also covers the side surface of the first current collector 11. On the other hand, in the second unit 50b, the oxygen vacancy portion 30 extends laterally from the peripheries of the first electrode 10 and the second electrode 20 and is arranged to cover the side surfaces of the first electrode 10 and the second electrode 20. Therefore, in the first unit 50a, the entire first electrode 10 and the second electrode 20 are covered by the oxygen vacancy portion 30. Similarly, in the second unit 50b, the entire first electrode 10 and the second electrode 20 are also covered by the oxygen vacancy portion 30. The oxygen vacancy portion 30 of the first unit 50a and the oxygen vacancy portion 30 of the second unit 50b are integrated with each other. By arranging the oxygen vacancy portion 30 in this way, it is possible to effectively prevent the first electrode 10 and the second electrode 20 from contacting each other in one unit.

[0043] Regarding the points not particularly described in the embodiments shown in FIGS. 4 and 5, the descriptions of the embodiments shown in FIGS. 1 to 3 are appropriately applied. Also, in FIGS. 4 and 5, the same members as those in FIGS. 1 to 3 are denoted by the same reference numerals.

[0044] As described above, the present invention has been described based on its preferred embodiments, but the present invention is not limited to the above embodiments. For example, the power storage device shown in FIGS. 4 and 5 may be housed in the housing 40 shown in either FIG. 2 or FIG. 3.

Example

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

[0046] 〔Example 1〕 Zirconium oxide powder manufactured by Tosoh Corporation and PVDF #1320 (N-methylpyrrolidone (NMP) solution with a solid content of 12 parts) manufactured by Kureha Corporation were mixed at a mass ratio of 94:6. The mixed solution was dispersed to obtain a slurry. This slurry was impregnated into Japanese paper with a thickness of 4 μm for 5 minutes. The Japanese paper impregnated with the slurry was vacuum dried at 120° C. for 12 hours. In this way, the oxygen vacancy portion 30 was obtained. A paint containing n-type tin oxide powder doped with antimony (manufactured by Mitsui Mining & Smelting Co., Ltd.) was applied to one surface of the oxygen vacancy portion 30 to form the second electrode 20. The n-type tin oxide paint was prepared according to the following procedure. MAC-350HC (cmc powder) manufactured by Nippon Paper Industries Co., Ltd. was added to pure water and stirred to a concentration of 1.4%. The n-type tin oxide powder was added thereto. Further, a binder BM-451B manufactured by Nippon Zeon Co., Ltd. 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 the first electrode 10. Two units 50 thus obtained were connected in series to form a stacked power storage device. The film formation 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. Charge and discharge evaluations were performed on this power storage device. The results are shown in Table 1 below.

[0047]

Table 1

[0048] As is clear from the results shown in Table 1, the power storage device of Example 1 can be charged at a high voltage, that is, it can be rapidly charged by stacking the units 50 composed of the first electrode 10, the oxygen vacancy portion 30, and the second electrode 20 in series. In addition, high-rate discharge can also be expected by connecting the units 50 in parallel. Therefore, in Example 2 described below, the increase in output power when a plurality of the units 50 are connected in parallel is examined.

[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 laminated power storage device was obtained in the same manner as in Example 1 except for this. The same evaluation as in Example 1 was performed on this power storage device. The results are shown in Table 2 below.

[0050]

Table 2

[0051] As shown in Table 2, it can be seen that the power storage device of Example 2 can be charged in a short time even when rapidly charged. Also, no heat generation was observed from this power storage device during rapid charging. Since the resistance |Z| of the power storage device is represented by the following formula (1), when the power 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 power storage device can be obtained above the capacity sum.

[0052]

Equation

[0053] 〔AC Impedance Measurement of the Power Storage Devices of Examples 1 and 2〕 AC impedance measurements were performed on the power storage devices of Examples 1 and 2. The AC impedance measurement was performed at room temperature of 25 °C and in the OC V state. The frequency range was set to 10 mHz to 10 kHz. The measuring device used was BCS810 (manufactured by Biologic). Fitting was performed on the Nyquist plot and its results by equivalent circuit analysis, and the sum of each measurement point calculated from the results was taken as the resistance |Z|. The results are shown in Table 3 below.

[0054]

Table 3

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

[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 vacancy part. 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. As zirconium oxide, that stabilized with the dopant shown in the same table was used. The amounts of the dopants shown in the same table are values with respect to stabilized zirconium oxide. Each substance was weighed, filled into a cell for pressure molding manufactured by Iject Co., Ltd., and then pressure-pressed to obtain an electric storage device. For the obtained electric storage device, the open-circuit voltage and the resistance (before charging) were measured. The results are shown in Table 4.

[0057]

Table 4

Claims

1. a first electrode including a p-type semiconductor; a second electrode including an n-type semiconductor; a power storage device comprising an oxygen vacancy portion disposed between the first electrode and the second electrode, wherein the oxygen vacancy portion contains a metal oxide, and in the metal oxide, the atomic ratio of oxygen element to metal element is smaller than the stoichiometric ratio.

2. The power storage device according to claim 1, wherein the oxygen vacancy portion contains zirconium oxide.

3. The power storage device includes a plurality of units each including the first electrode, the oxygen vacancy portion, and the 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 power storage device according to claim 2, wherein the oxygen vacancy portion contains zirconium oxide stabilized by yttrium oxide, cerium oxide, calcium oxide, magnesium oxide, or scandium oxide.

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

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