Capacitor type power storage device

Abstract

To provide a capacitor type power storage device having high energy density, short charge time, and excellent cycle stability.SOLUTION: A capacitor type power storage device of the present invention includes a first electrode, a second electrode, and a dielectric layer located between the first electrode and the second electrode. The dielectric layer comprises a laminate of nanosheet monolayer films, the nanosheet monolayer film each being represented by general formula An-1M3Tin-3O3n+1-d (where, n≥4 and 0≤d≤1 are satisfied, A element represents at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lead (Pb), and bismuth (Bi), and M element represents niobium (Nb) and / or tantalum (Ta)).SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a capacitor-type storage device. [Background technology]

[0002] High-performance energy storage devices are a key technology for achieving long- and medium-term environmental and energy challenges, such as reducing greenhouse gas emissions and achieving the SDGs, and research and development into these devices is being actively conducted around the world. High-performance energy storage devices, such as lithium secondary batteries and electric double-layer capacitors, are being developed and put into practical use. These energy storage devices utilize rare metals, such as lithium and cobalt, which poses an element strategy challenge. Furthermore, using electrolytes in energy storage devices presents challenges, such as long charging times, electrolyte degradation and lifespan, and safety.

[0003] In contrast to this, dielectric capacitors using dielectrics are known (see, for example, Non-Patent Documents 1 and 2). In Non-Patent Document 1, Ca2Nb3O 10 Au / (Ca2Nb3O 10 )n / SrRuO3 capacitor (n=3), 350MVm -1 This suggests its application to electricity storage devices.

[0004] In Non-Patent Document 2, (Ca2Na m-3 Nb m O 3m+1 ) (m = 3-6) nanosheet laminates, Au / (Ca2Na m-3 Nb m O 3m+1 )n / SrRuO3 capacitors (n = 5, 8) are suggested for use in energy storage devices. However, for these nanosheets to be put to practical use as energy storage devices, improvements in energy density, short charging times, and cycle stability are required.

[0005] On the other hand, general formula A n-1 M3Ti n-3 O 3n+1 -It has been reported that perovskite nanosheets represented by the formula (n≧4, A is an element selected from the group consisting of Mg, Ca, Sr, and Ba) function as dielectric materials (see, for example, Patent Document 1). However, the dielectric properties of the perovskite nanosheets described in Patent Document 1 are not fully known, and the development of suitable applications is desired. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-152052 [Non-patent literature]

[0007] [Non-Patent Document 1] Minoru Osada et al., ACS Nano 2010, 4, 9, 5225-5232 [Non-patent document 2] Bao-Wen Li,J.Am.Chem.Soc.,2017,139,31,10868-10874 Summary of the Invention [Problem to be solved by the invention]

[0008] In view of the above, an object of the present invention is to provide a capacitor-type electricity storage device having high energy density, short charging time, and excellent cycle stability. [Means for solving the problem]

[0009] The capacitor-type electricity storage device according to the present invention comprises a first electrode, a second electrode, and a dielectric layer located between the first electrode and the second electrode, the dielectric layer comprising a compound represented by general formula A n-1 M3Ti n-3 O 3n+1-d(wherein n≧4, 0≦d≦1, the A element is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lead (Pb) and bismuth (Bi), and the M element is niobium (Nb) and / or tantalum (Ta), thereby solving the above-mentioned problem. The nanosheet monolayer film has the general formula K[A n-1 M3Ti n-3 O 3n+1-d The inorganic layer may be a film obtained by peeling off a single layer from an inorganic layered material represented by the formula: The A element may be Sr and / or Ca. The M element may be Nb. The thickness of the nanosheet monolayer film may be in the range of 0.5 nm to 10 nm. The thickness of the dielectric layer may be in the range of 1 nm to 100 nm. The defect density in the dielectric layer may be in the range of 1% to 7%. The dielectric layer may have a relative permittivity in the range of 700 to 2000, and a band gap in the range of 3 eV to 5 eV. The energy density is 5 x 10 2 J / cm 3 More than 1×10 5 J / cm 3 The following ranges may also be used: The distortion of the NbO6 octahedron may be in the range of 3° to 10°. The first electrode may be selected from the group consisting of conductive perovskite oxides, transparent conductive oxide films, and metals. The conductive perovskite oxide may be selected from the group consisting of strontium ruthenate (SrRuO), calcium ruthenate (CaRuO), strontium vanadate (SrVO), strontium chromate (SrCrO), strontium cobaltate (SrCoO), lanthanum niobate (LaNiO), niobium-doped strontium titanate (SrTiO:Nb), and lanthanum-doped strontium titanate (SrTiO:La). The transparent oxide conductive film may be selected from the group consisting of tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), boron-doped zinc oxide (BZO), and niobium-doped titanium oxide (TNO). The metal may be selected from the group consisting of gold (Au), platinum (Pt), copper (Cu), and nickel (Ni). The second electrode may be selected from the group consisting of gold (Au), platinum (Pt), copper (Cu), and nickel (Ni). The thickness of the first electrode may be in the range of 10 nm to 10 μm. The second electrode may have a thickness in the range of 5 nm to 1 μm. [Effects of the Invention]

[0010] The capacitor-type electricity storage device of the present invention comprises a first electrode, a second electrode, and a dielectric layer positioned therebetween, the dielectric layer being formed of a compound represented by general formula A n-1 M3Ti n-3 O 3n+1-d(where n≧4, 0≦d≦1, the element A is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lead (Pb), and bismuth (Bi), and the element M is niobium (Nb) and / or tantalum (Ta). Because the nanosheet monolayer film does not contain any mobile monovalent alkali metal ions, it is possible to improve cycle stability and achieve a short charge time even under high electric field application. Furthermore, by substituting Ti for Nb, it is possible to improve the relative permittivity and energy density. Such a capacitor-type power storage device achieves both an energy density exceeding that of lithium secondary batteries and an output density exceeding that of dielectric capacitors, while also achieving cycle stability and a short charge time. [Brief explanation of the drawings]

[0011] [Figure 1] Schematic diagram showing an electricity storage device of the present invention. [Figure 2] Illustrative Flowchart for Manufacturing the Electrical Storage Device of the Present Invention [Figure 3] Schematic diagram and cross-sectional TEM image of the electricity storage device of Example 1 [Figure 4] 10A and 10B are diagrams showing the leakage current characteristics and withstand voltage of the electricity storage devices of Examples 1 and 2. [Figure 5] Graph showing frequency dependence of relative permittivity and dielectric loss of the electricity storage devices of Examples 1 and 2 [Figure 6] Graph showing the charge / discharge characteristics of the electricity storage device of Example 1 [Figure 7] Graph showing changes in energy density of the electricity storage devices of Examples 1 and 2 [Figure 8] FIG. 1 shows the charge-discharge cycle stability of the energy density of the power storage device of Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. Note that like elements are designated by like numbers and their description will be omitted. The present invention relates to a capacitor-type electricity storage device. In this specification, the electricity storage device is a device in which a high voltage is applied to a high dielectric material having high withstand voltage characteristics, resulting in a high polarization state and high energy density, and is different from capacitor elements and capacitors used in electronic devices, which require low voltage use and low power consumption.

[0013] In detail, the capacitor-type electricity storage device of the present invention is -1 Over 1000MVm -1 Apply a high electric field of 5×10 1 Jcm -3 More than 1×10 5 Jcm -3 The following ranges of energy densities are available:

[0014] FIG. 1 is a schematic diagram showing an electricity storage device of the present invention.

[0015] The electricity storage device 100 of the present invention includes a first electrode 110, a second electrode 120, and a dielectric layer 130 located between the first electrode 110 and the second electrode 120. Furthermore, in the electricity storage device 100 of the present invention, the dielectric layer 130 is made of a laminate of nanosheet monolayer films 140.

[0016] Here, the nanosheet monolayer film 140 constituting the dielectric layer 130 is intended to be a film formed by densely arranging nanosheets obtained by exfoliating an inorganic layered material into single layers without overlapping. The dielectric layer 130 may be a multilayer film in which the same type of nanosheet monolayer film is laminated, or a multilayer film in which two or more different types of nanosheet monolayer films are combined and laminated.

[0017] Among the various reported nanosheets exhibiting dielectric properties, the present inventors have found nanosheets of general formula A n-1 M3Ti n-3 O 3n+1-dIt has been discovered that by selecting nanosheets represented by the formula (where n≧4, 0≦d≦1, element A is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lead (Pb) and bismuth (Bi), and element M is niobium (Nb) and / or tantalum (Ta)), and employing a dielectric layer made of this laminate (i.e., a laminate of nanosheet monolayer films), high energy density, short charging time and stable cycle characteristics are possible, making it possible to provide an electricity storage device. The parameter d is a range that takes into account charge compensation by oxygen.

[0018] Ca2Na described in Non-Patent Documents 1 and 2 m-3 Nb m O 3m+1 In nanosheets, monovalent Na + The present inventors have identified that monovalent alkali metal ions are called mobile ions, and that they are mobile under the application of a high electric field, and therefore have negative effects on electricity storage devices, such as limiting the charge / discharge rate and deteriorating cycle stability. Based on this knowledge, nanosheets that do not contain mobile ions such as Na ions are preferred for electricity storage devices that are applied with a high electric field, and the above-mentioned A n-1 M3Ti n-3 O 3n+1 We have now adopted nanosheets expressed as follows:

[0019] Furthermore, surprisingly, the Ca2Na m-3 Nb m O 3m+1 It was found that by substituting Ti for part of the Nb in the nanosheet, the relative permittivity and energy density were significantly improved. n-1 M3Ti n-3 O 3n+1-d It has been confirmed that the nanosheet represented by the formula (I) is effective for power storage devices.

[0020] General formula A n-1 M3Ti n-3 O 3n+1-dThe nanosheets represented by the formula (1) contain a combination of MO6 octahedral blocks and TiO6 octahedral blocks, and the ratio of these can be artificially designed.

[0021] The element A is preferably Sr and / or Ca. These elements distort the NbO6 octahedron blocks, thereby improving the dielectric constant and energy density. The element A is more preferably Sr. This further enhances the distortion of the NbO6 octahedron blocks, resulting in high polarization and further improving the dielectric constant and energy density.

[0022] The distortion of the NbO6 octahedral blocks can be evaluated by Raman spectroscopy, and preferably satisfies a rotational distortion of 3° or more of the octahedral blocks. This allows for even higher polarization, leading to further improvements in the dielectric constant and energy density. There is no particular upper limit, but it is preferably 10° or less.

[0023] Such inorganic layered materials have the general formula K[A n-1 M3Ti n-3 O 3n+1-d

[0023] The inorganic layered material is represented by the formula: K is potassium, the A element is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lead (Pb) and bismuth (Bi), and the M element is niobium (Nb) and / or tantalum (Ta).

[0024] The single layer peeling treatment of the inorganic layered material is called a soft chemical treatment, which is a combination of an acid treatment and a colloidal treatment. For example, see Patent Document 1.

[0025] The thickness of the nanosheet monolayer film 140 is preferably in the range of 0.5 nm to 10 nm, inclusive, in which case a large relative dielectric constant and a large band gap can be obtained due to the size effect.

[0026] The thickness of the dielectric layer 130 is sufficient as long as the nanosheet monolayer film 140 is laminated, and preferably satisfies the range of 1 nm to 100 nm. Within this range, the above-mentioned relative dielectric constant and high dielectric breakdown strength are achieved. More preferably, the thickness of the dielectric layer 130 is within the range of 5 nm to 50 nm.

[0027] The dielectric layer 130 used in the power storage device 100 preferably has a relative permittivity in the range of 700 to 2000, both inclusive. This allows for improved energy density. Furthermore, the dielectric layer 130 preferably has a band gap in the range of 3 eV to 5 eV, both inclusive. This increases the dielectric breakdown strength, allowing for improved energy density. While existing dielectrics have an inverse correlation between the dielectric constant and the dielectric breakdown strength, the dielectric layer 130 of the present invention differs from this inverse correlation by having a correlation in which the relative permittivity and the dielectric breakdown strength both increase.

[0028] The dielectric layer 130 more preferably has a relative dielectric constant in the range of 750 to 1200. The dielectric layer 130 more preferably has a band gap in the range of 3.5 eV to 3.9 eV, thereby further improving the energy density.

[0029] The dielectric layer 130 preferably has a defect density in the range of 1% to 7%. This allows for high dielectric breakdown strength. The dielectric layer 130 more preferably has a defect density in the range of 2% to 5%. The defect density is calculated from the area of ​​the uncovered portion of the nanosheet using atomic force microscope image analysis software (Nano Navi, version 5.02, manufactured by SII Nano Technology).

[0030] The first electrode 110 is preferably selected from the group consisting of conductive perovskite oxides, transparent conductive oxide films, and metals, which have low contact resistance with the nanosheet monolayer film.

[0031] The conductive perovskite oxide is illustratively selected from the group consisting of strontium ruthenate (SrRuO), calcium ruthenate (CaRuO), strontium vanadate (SrVO), strontium chromate (SrCrO), strontium cobaltate (SrCoO), lanthanum niobate (LaNiO), niobium-doped strontium titanate (SrTiO:Nb), and lanthanum-doped strontium titanate (SrTiO:La).

[0032] The transparent oxide conductive film is selected from the group consisting of tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), boron-doped zinc oxide (BZO), and niobium-doped titanium oxide (TNO).

[0033] The metal is selected from the group consisting of gold (Au), platinum (Pt), copper (Cu), and nickel (Ni). Other metals that may be used include silver (Ag), iron (Fe), tin (Sn), zinc (Zn), aluminum (Al), indium (In), and chromium (Cr).

[0034] There are no particular limitations on the thickness of the first electrode 110, but it may preferably be in the range of 10 nm to 10 μm. If the thickness is in this range, the first electrode 110 made of a single crystal substrate can be used. Alternatively, if the first electrode 110 is not a single crystal substrate, it is preferable that the first electrode 110 be provided on a substrate. This facilitates the implementation of the manufacturing process described below.

[0035] The second electrode 120 is preferably made of the same metal as the first electrode 110, and is illustratively selected from the group consisting of gold (Au), platinum (Pt), copper (Cu), and nickel (Ni). There are no particular limitations on the thickness of the second electrode 120, but as long as it is made of the above-mentioned metals, it may be in the range of 5 nm to 1 μm. If the thickness is within this range, the second electrode 120 can be applied by physical vapor deposition or the like.

[0036] The electricity storage device 100 of the present invention preferably has a capacity of 5×10 2 J / cm 3 More than 1×10 5 J / cm 3 Furthermore, the power storage device 100 of the present invention preferably achieves an energy density in the range of 1×10 2 MW / cm 3 5x10 or more 4 MW / cm 3 The following range of power density is achieved: As described above, by employing the above-described nanosheet, it is possible to provide an electricity storage device that achieves both high energy density and high power density.

[0037] FIG. 2 is an exemplary flowchart for manufacturing the electricity storage device of the present invention.

[0038] Step S210: A colloidal dispersion is prepared in which nanosheets obtained by exfoliating an inorganic layered material are dispersed in a dispersion medium. Step S220: Using the colloidal dispersion, a laminate of nanosheet monolayer films is formed on the first electrode. Step S230: A second electrode is formed on the laminate of nanosheet monolayer films. By the above method, the above-described electricity storage device 100 of the present invention is obtained. The inorganic layered material, the first electrode, and the second electrode are as described above, and therefore a description thereof will be omitted.

[0039] Each step will be described in detail. In step S210, the powder of the inorganic layered material is brought into contact with an aqueous solution of an acid such as hydrochloric acid, and the resulting product is filtered, washed, and then dried. This replaces all the alkali metal ions present between the layers before the treatment with hydrogen ions or oxonium ions, yielding a hydrogen ion exchanger. Next, the resulting hydrogen ion exchanger is treated with tetrabutylammonium ions (TBA +When the nanoparticles are placed in an aqueous solution containing basic substances such as tetrapropylammonium ions, tetraethylammonium ions, tetramethylammonium ions, n-propylamine, n-ethylamine, and ethanolamine and stirred, they become colloidal. In this way, the layers that made up the layered structure are peeled off one by one, yielding nanosheets. For details of this process, see, for example, Patent Document 1.

[0040] In step S220, the first electrode may be a substrate provided with a thin film made of the above-mentioned material, or may be a single crystal or polycrystalline substrate made of the above-mentioned material, or a metal substrate. A substrate is easy to handle, and therefore, it is easy to form a laminate of nanosheet monolayer films.

[0041] In addition, when the first electrode is a thin film on a substrate, the thin film may be formed by a physical vapor deposition method such as sputtering, resistance heating evaporation, electron beam evaporation, molecular beam epitaxy, or ion plating, or a chemical vapor deposition method such as thermal CVD, photo CVD, plasma CVD, atomic layer deposition, or metal organic chemical vapor deposition.

[0042] In step S220, a method selected from the group consisting of the Langmuir-Blodgett (LB) method, the layer-by-layer (LBL) method, the spin coating method, the dropping method, the slit coating method, the bar coating method, and the dip coating method is preferably used to form a laminate of nanosheet monolayer films.

[0043] The LB method is a technique for forming nanosheet monolayer films using surface pressure. A colloidal dispersion is spread in a trough (water tank) in which a first electrode is immersed, and nanosheets are suspended at the gas-liquid interface. The surface of the colloidal dispersion is compressed to a certain surface pressure to form a gas-liquid interface, and then the first electrode is pulled up vertically. This transfers the nanosheet monolayer film onto the first electrode. By repeating this process, a stack of nanosheet monolayer films is formed on the first electrode.

[0044] With the LB method, nanosheets do not overlap with each other on the surface of the developer, and a monolayer film in which nanosheets are accumulated in the planar direction is formed at the air-liquid interface, making it possible to form an extremely uniform and high-quality nanosheet monolayer film on the first electrode.

[0045] The LBL method, also known as the layer-by-layer adsorption method, is a technique for forming a nanosheet monolayer film using electrostatic interactions. Counterions (e.g., cationic polymers) are applied to a first electrode, followed by a colloidal dispersion. This causes electrostatic interactions with the counterions, resulting in the nanosheets being firmly bonded to form a nanosheet monolayer film. This process is repeated until the desired thickness is achieved, and the counterions are removed by irradiating with light such as ultraviolet light. This results in the formation of a nanosheet monolayer film laminate on the first electrode.

[0046] The spin coating method uses a colloidal dispersion as the spin coating material. The colloidal dispersion is dropped onto a first substrate rotating at high speed, and centrifugal force is used to obtain a laminate consisting of a uniform nanosheet monolayer film. The spin coating method makes it relatively easy to obtain a laminate consisting of a uniform nanosheet monolayer film.

[0047] The dropping method involves dropping a colloidal dispersion onto the first electrode using a pipette or the like and then drying it, thereby obtaining a laminate consisting of a nanosheet monolayer film.

[0048] The dip coating method involves immersing the first electrode in a colloidal dispersion, then lifting it out and drying it. As with the drop coating method, this method also produces a laminate consisting of a nanosheet monolayer film.

[0049] Bar coating and slit coating methods can also be employed using existing methods with colloidal dispersions.

[0050] In step S230, a thin film that will become the second electrode described above may be formed on the laminate obtained in step S220 by a physical vapor deposition method such as sputtering, resistance heating evaporation, electron beam evaporation, molecular beam epitaxy, or ion plating, or a chemical vapor deposition method such as thermal CVD, photo-CVD, plasma CVD, atomic layer deposition, or metal organic chemical vapor deposition. In this manner, the electricity storage device 100 (FIG. 1) of the present invention is manufactured.

[0051] The present invention will now be described in detail using specific examples, but it should be noted that the present invention is not limited to these examples. [Example]

[0052] [Example 1] In Example 1, the general formula A n-1 M3Ti n-3 O 3n+1-d An electricity storage device was manufactured having a laminate of 10 nanosheet monolayer films, each of which has n=4, d=0, the A element being Sr, and the M element being Nb.

[0053] Inorganic layered material KSr3Nb3TiO 13 is KSr2Nb3O 10 and SrTiO3 in a molar ratio of 1:1, and calcined at 1273 K for 24 hours. 5 g of the obtained powder was added to 200 cm3 of 5N nitric acid solution at room temperature. 3 0.4 g of this hydrogen ion exchanger was added to 100 cm of an aqueous solution of tetrabutylammonium hydroxide (hereinafter referred to as TBAOH). 3 The mixture was stirred at room temperature for 7 days and reacted to form a compound with the composition formula Sr3Nb3TiO 13 We prepared a milky white sol solution (colloidal dispersion) in which rectangular nanosheets with a thickness of approximately 2 nm and a width of approximately 10 μm were dispersed.

[0054] Using the colloidal dispersion, a laminate consisting of a nanosheet monolayer film was formed as the first electrode on a SrRuO3 single crystal substrate by the LB method. The SrRuO3 single crystal substrate was irradiated with ultraviolet light in an ozone atmosphere and the surface was cleaned.

[0055] 1dm 3 Add 8 cm of colloidal dispersion to a measuring flask. 3 The SrRuO3 single crystal substrate was then placed in an LB trough that had been thoroughly washed with acetone, and the resulting solution was dispersed in ultrapure water. The solution was then placed in an LB trough that had been thoroughly washed with acetone and the temperature of the lower layer was allowed to stabilize. The SrRuO3 single crystal substrate was then placed in an LB film-forming apparatus. The following series of operations constituted one cycle, and these were repeated 10 times to form a laminate consisting of a nanosheet monolayer film. (1) The barrier is moved at a compression speed of 0.5 mm / min to compress the surface, gathering together the nanosheets dispersed on the gas-liquid interface, and after a constant pressure is reached, the mixture is left to stand for 30 minutes. (2) By vertically pulling up the SrRuO3 single crystal substrate at a pulling rate of 0.8 mm / min and attaching the nanosheets gathered on the gas-liquid interface to the substrate, a nanosheet monolayer film is formed in which the nanosheets are densely arranged without overlapping.

[0056] The resulting laminate was irradiated with ultraviolet light (wavelength: 200 to 300 nm, intensity: 1 mW / cm) using a xenon light source. 2 ) for 72 hours to decompose and remove organic substances such as TBAOH used as a release agent. Next, a gold dot electrode (100 μmφ) was deposited as a second electrode on the laminate using a vacuum deposition apparatus (Sanyu Electronics Co., Ltd., SVC-700), thereby producing the electricity storage device of Example 1. Before depositing the gold dot electrode, the distortion of the NbO6 octahedra in the laminate was evaluated using a Raman spectrometer (Horiba Jobin-Yvon Co., Ltd., Model No. T64000), and was found to be 7°.

[0057] The cross section of the energy storage device in Example 1 was observed using a transmission electron microscope (Hitachi High-Technologies Corporation, H-9000). The cross-sectional observation results are shown in Figure 3. The surface was also observed using an atomic force microscope (SII NanoTechnology Corporation, E-Sweep) to determine the nanosheet coverage and calculate the defect density. As a reference sample, a laminate was fabricated on a quartz glass substrate under the same conditions as the SrRuO3 single crystal substrate, and the band gap was calculated from the absorption spectrum. The band gap was calculated by linear extrapolation to be 3.81 eV, which is larger than the value (3.2 eV) of the conventional bulk material BaTiO3, and is expected to improve dielectric breakdown strength.

[0058] The leakage current density, dielectric breakdown strength, and relative dielectric constant of the electricity storage device of Example 1 were measured. The leakage current density was measured using a Keithley Semiconductor Parameter Analyzer (4200-SCS) at an applied voltage of 100 MVm -1 The current density was measured when a voltage was applied. The applied voltage was also increased to examine the dielectric breakdown strength (voltage resistance). The relative dielectric constant was calculated by measuring the capacitance at a frequency of 10 kHz using an Agilent Technologies high-precision LCR meter (4284A).

[0059] The charge / discharge characteristics and cycle characteristics of the energy storage device of Example 1 were measured. Electric pulses of different pulse widths were applied to the energy storage device, and the change in charge amount was measured using a high resistance meter (Keithley, 6517A). The pulse width was varied from 10 μs to 1 ms using an arbitrary waveform generator (TEGAM, 2414B). These results are shown in Figures 4 to 8 and Table 2, and are described in detail.

[0060] [Example 2] In Example 2, the general formula A n-1 M3Ti n-3 O 3n+1-d An electricity storage device was manufactured having a laminate of 10 nanosheet monolayer films, where n=4, d=0, A element is Ca, and M element is Nb. 10 and KCa2Nb3O instead of SrTiO3 10The electricity storage device of Example 2 obtained in this manner was evaluated in the same manner as Example 1. The results are shown in Fig. 4, Fig. 5, Fig. 7 and Table 2, and are described in detail.

[0061] [Example 3] In Example 3, the general formula A n-1 M3Ti n-3 O 3n+1-d An electricity storage device was manufactured having a laminate of 10 nanosheet monolayer films, where n=5, d=0, the A element is Sr, and the M element is Nb. 10 The explanation will be omitted here because it is the same as Example 1 except that the molar ratio of SrTiO3 to SrTiO3 was 1:2. The electricity storage device of Example 3 obtained in this manner was evaluated in the same manner as Example 1. The results are shown in Table 2 and are described in detail.

[0062] [Example 4] In Example 4, the general formula A n-1 M3Ti n-3 O 3n+1-d An electricity storage device was manufactured having a laminate of 10 nanosheet monolayer films, where n=5, d=0, A element is Ca, and M element is Nb. 10 and KCa2Nb3O instead of SrTiO3 10 and CaTiO3 were used in a molar ratio of 1:2, and other than this, the procedure is the same as in Example 1, and therefore a description thereof will be omitted. The electricity storage device of Example 4 obtained in this manner was evaluated in the same manner as in Example 1. The results are shown in Table 2 and are described in detail.

[0063] [Example 5] In Example 5, Ca2Nb3O 10 We fabricated an electricity storage device with a laminate consisting of 10 layers of KCa2Nb3O nanosheet monolayers. 10 An electricity storage device was produced by the LB method in the same manner as in Example 1, except that the electricity storage device of Example 5 obtained in this manner was evaluated in the same manner as in Example 1. The results are shown in Table 2 and are described in detail.

[0064] [Example 6] In Example 6, Ca2NaNb4O 13 We fabricated an electricity storage device with a laminate consisting of 10 layers of nanosheet monolayer films. 13 An electricity storage device was produced by the LB method in the same manner as in Example 1, except that the electricity storage device of Example 6 obtained in this manner was evaluated in the same manner as in Example 1. The results are shown in Table 2 and are described in detail.

[0065] [Example 7] In Example 7, Ca2Na2Nb5O 16 We fabricated an electricity storage device with a laminate consisting of 10 layers of nanosheet monolayer films. 16 An electricity storage device was produced by the LB method in the same manner as in Example 1, except that the electricity storage device of Example 7 obtained in this manner was evaluated in the same manner as in Example 1. The results are shown in Table 2 and are described in detail.

[0066] [Example 8] In Example 8, Ca2Na3Nb6O 19 We fabricated an electricity storage device with a laminate consisting of 10 layers of nanosheet monolayer films. 19 An electricity storage device was produced by the LB method in the same manner as in Example 1, except that the electricity storage device of Example 8 obtained in this manner was evaluated in the same manner as in Example 1. The results are shown in Table 2 and are described in detail.

[0067] For simplicity, the configurations of the electricity storage devices shown in Examples 1 to 8 are shown in Table 1, and the results are shown in Table 2, which will be explained together.

[0068] [Table 1]

[0069] [Table 2]

[0070] FIG. 3 is a diagram showing a schematic diagram and a cross-sectional TEM image of the electricity storage device of Example 1.

[0071] As shown in Figure 3, a laminate was formed on the SrRuO3 single crystal substrate, and the laminate had a clear lamellar structure, confirming the presence of 10 nanosheet monolayer films. The thickness of the laminate, i.e., the dielectric layer, was 20 nm. The interface between the substrate and the laminate, and the interface between the laminate and the gold electrode, were free of interdiffusion and were flat and clear at the atomic level. Furthermore, the defect density calculated using AFM was 3%. Although not shown, the electricity storage devices of Examples 2 to 8 also exhibited similar TEM images, with defect densities of 5% or less.

[0072] FIG. 4 is a diagram showing the leakage current characteristics and withstand voltage of the electricity storage devices of Examples 1 and 2. In FIG.

[0073] The leakage current density of the energy storage devices in Examples 1 and 2 was 100 MVm -1 1 x 10 -8 Acm -2 The withstand voltage of the electricity storage devices of Examples 1 and 2 was 390 MVm or less. -1 and 410MVm -1 The leakage current was also small in the electricity storage devices of Examples 3 and 4, and the withstand voltage was 380 MVm. -1 It exceeded that.

[0074] FIG. 5 is a graph showing the frequency dependence of the relative permittivity and dielectric loss of the electricity storage devices of Examples 1 and 2. In FIG.

[0075] The relative permittivity of the electricity storage devices of Examples 1 and 2, which contained Ti, was 940 and 780, respectively, and the dielectric loss was also small. Furthermore, the dielectric properties of the electricity storage devices of Examples 1 and 2 were stable over a wide range of 1 to 2 MHz. Similarly, as shown in Table 2, the relative permittivity of the electricity storage devices of Examples 3 and 4 was also stable, exceeding 800. On the other hand, the relative permittivity of the electricity storage devices of Examples 5 to 8, which did not contain Ti, was less than 500. This demonstrates that the inclusion of Ti dramatically improves the relative permittivity.

[0076] Sr3Nb3TiO used in the energy storage device of Example 1 13 The distortion of the NbO6 octahedron in the nanosheet is 7°, and the Ca3Nb3TiO 13 This was found to be larger than that of the NbO6 octahedron in the nanosheet (5°), suggesting that the dielectric properties improve as the distortion of the NbO6 octahedron increases.

[0077] FIG. 6 is a graph showing the charge and discharge characteristics of the electricity storage device of Example 1.

[0078] As shown in Figure 6, it was found that the electricity storage device of Example 1, which did not contain Na ions, completed both charging and discharging in an extremely short time of approximately 0.5 μs. As shown in Table 2, the charging times of the electricity storage devices of Examples 2 to 4 were all 0.5 μs or less. On the other hand, the charging times of the electricity storage devices of Examples 5 to 8, which contained Na ions, exceeded 5 μs. This suggests that the absence of Na ions, which are mobile ions, improves the charge and discharge characteristics.

[0079] FIG. 7 is a diagram showing changes in energy density of the electricity storage devices of Examples 1 and 2. In FIG.

[0080] According to FIG. 7, the energy density of the Ti-containing electricity storage devices of Examples 1 and 2 was 400 MVm -1 At high electric fields, respectively, -3 and 516 Jcm -3 As shown in Table 2, the energy density of the energy storage devices of Examples 3 and 4 reached 780 Jcm -3 and 620 Jcm -3 On the other hand, the energy density of the electricity storage devices of Examples 4 to 8, which did not contain Ti, was 272 Jcm at most. -3 This indicates that the inclusion of Ti significantly improves the energy density.

[0081] The output density of the power storage devices of Examples 1 to 8 was calculated by dividing the energy density by the charge / discharge time, and was 500 MWcm as shown in Table 2. -3 However, it exceeded 500MWcm -3 and a power density of over 500 Jcm -3 Only the electricity storage devices of Examples 1 to 4 achieved both of the above energy densities, demonstrating that they are superior electricity storage devices that surpass lithium secondary batteries.

[0082] FIG. 8 is a graph showing the charge-discharge cycle stability of the energy density of the electricity storage device of Example 1.

[0083] Cycle stability is 200MVm -1 After applying a 10 kHz triangular wave, the behavior of the electric displacement and electric field (DE loop) was measured for up to 10 8 As shown in FIG. 8, the energy density of the electricity storage device of Example 1 containing no Na ions was 10 8 Although not shown, the energy density of the electricity storage devices of Examples 2 to 4 also showed similar behavior. On the other hand, the energy density of the electricity storage devices of Examples 5 to 8 containing Na ions was 10 6 This indicates that the absence of mobile Na ions improves cycle stability. [Industrial Applicability]

[0084] The power storage device of the present invention has a high energy density, a short charging time, and excellent cycle stability, and can therefore be used as a battery replacement for mobile terminals, as an energy regeneration system for electric vehicles / hybrid vehicles, for power storage, and the like. [Explanation of symbols]

[0085] 100 Energy storage device 110 first electrode 120 Second electrode 130 Dielectric layer 140 Nanosheet monolayer film

Claims

1. The first electrode and The second electrode and The device comprises a dielectric layer located between the first electrode and the second electrode, The dielectric layer is based on general formula A ｎ－１ M ３ Ti ｎ－３ O ３ｎ＋１－ｄ A capacitor-type energy storage device comprising a laminate of nanosheet monolayer films represented as follows: (where n≧4, 0≦d≦1, element A is at least one element selected from the group consisting of magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), lead (Pb), and bismuth (Bi), and element M is niobium (Nb) and / or tantalum (Ta)).

2. The aforementioned nanosheet monolayer film has the general formula K[A ｎ－１ M ３ Ti ｎ－３ O ３ｎ＋１－ｄ The energy storage device according to claim 1, wherein the film is a single layer peeled off from an inorganic layered material represented by [ ].

3. The energy storage device according to claim 1 or 2, wherein the element A is Sr and / or Ca.

4. The energy storage device according to any one of claims 1 to 3, wherein the aforementioned M element is Nb.

5. The energy storage device according to any one of claims 1 to 4, wherein the thickness of the nanosheet monolayer film is in the range of 0.5 nm to 10 nm.

6. The energy storage device according to any one of claims 1 to 5, wherein the thickness of the dielectric layer is in the range of 1 nm to 100 nm.

7. The energy storage device according to any one of claims 1 to 6, wherein the defect density in the dielectric layer is in the range of 1% to 7%.

8. The relative permittivity of the dielectric layer satisfies the range of 700 to 2000. The energy storage device according to any one of claims 1 to 7, wherein the band gap of the dielectric layer is in the range of 3 eV to 5 eV.

9. The energy density is 5×10 ２ J / cm ３ or more and 1×10 ５ J / cm ３ or less, the electricity storage device according to any one of claims 1 to 8.

10. NboO ６ The energy storage device according to any one of claims 1 to 9, wherein the distortion of the octahedron is in the range of 3° to 10°.

11. The energy storage device according to any one of claims 1 to 10, wherein the first electrode is selected from the group consisting of conductive perovskite oxide, transparent oxide conductive film, and metal.

12. The conductive perovskite oxide is strontium ruthenate (SrRuO ３ ), calcium ruthenate (CaRuO ３ ), strontium vanadate (SrVO ３ ), strontium chromate (SrCrO ３ ), strontium cobaltate (SrCoO ３ ), lanthanum niobate (LaNiO ３ ), niobium-doped strontium titanate (SrTiO ３ :Nb), and lanthanum-doped strontium titanate (SrTiO ３ The energy storage device according to claim 11, selected from the group consisting of :La).

13. The energy storage device according to claim 11, wherein the transparent oxide conductive film is selected from the group consisting of tin-doped indium oxide (ITO), aluminum-doped zinc oxide (AZO), antimond-doped tin oxide (ATO), boron-doped zinc oxide (BZO), and niobium-doped titanium oxide (TNO).

14. The energy storage device according to claim 11, wherein the metal is selected from the group consisting of gold (Au), platinum (Pt), copper (Cu), and nickel (Ni).

15. The energy storage device according to any one of claims 1 to 14, wherein the second electrode is selected from the group consisting of gold (Au), platinum (Pt), copper (Cu), and nickel (Ni).

16. The energy storage device according to any one of claims 1 to 15, wherein the thickness of the first electrode is in the range of 10 nm or more and 10 μm or less.

17. The energy storage device according to any one of claims 1 to 16, wherein the thickness of the second electrode is in the range of 5 nm to 1 μm.

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