Method for storing an electricity storage device and system for storing an electricity storage device

Abstract

To provide a technique for suppressing self-discharge of a power storage device by storing the power storage device for a long period of time at a temperature suitable for the power storage device.SOLUTION: A power storage device includes a container filled with an electrolytic solution, metal atoms that are ionized in the electrolytic solution and involved in charging and discharging, and an electrode disposed in the electrolytic solution, and is configured such that a layer of the metal atoms in which the metal atoms are precipitated is formed on a surface of the electrode during charging. The method for storing a power storage device includes charging the power storage device, and bringing the charged power storage device into an open circuit state and maintaining the temperature of the power storage device at a predetermined storage temperature of 25 °C or higher and 65 °C or lower.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present application relates to a method for storing an electricity storage device and a system for storing an electricity storage device. [Background technology]

[0002] Known examples of chargeable and dischargeable electricity storage devices include secondary batteries, electric double layer capacitors, etc. Known secondary batteries include, for example, lithium ion batteries in which lithium ions are involved in charging and discharging.

[0003] Conventional lithium-ion batteries have generally been stored at temperatures lower than room temperature. The reason for this is that storing them in a high-temperature environment above room temperature for a long period of time may accelerate internal chemical reactions, making them more susceptible to self-discharge, or may cause a coating to form on the electrode surface, resulting in performance degradation. For example, Patent Document 1 listed below discloses a technique for storing lithium-ion batteries at temperatures between 0°C and -40°C. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-210612 Summary of the Invention [Problem to be solved by the invention]

[0005] Conventional lithium-ion batteries such as those disclosed in Patent Document 1 are charged by intercalation, in which lithium ions enter between the layer structures of the crystalline electrode material. In contrast, the inventors of the present invention, through extensive research into energy storage devices, have developed an energy storage device that is charged by an electrode reaction different from intercalation. The inventors of the present invention have found that self-discharge of such an energy storage device can be suppressed by storing it in a temperature range other than the low temperatures mentioned above. If self-discharge during long-term storage of an energy storage device can be suppressed, the power of the energy storage device can be used more effectively.

[0006] An object of the present application is to provide a technology for suppressing self-discharge of an electricity storage device by storing the electricity storage device for a long period of time at a temperature suitable for the electricity storage device. [Means for solving the problem]

[0007] The present invention is based on the findings that the inventor of the present invention independently obtained in the course of researching electricity storage devices that are charged by electrode reactions different from intercalation, and can be realized, for example, in the following forms.

[0008] One aspect of the present invention is provided as a method for storing an electricity storage device. This storage method includes the steps of: charging an electricity storage device comprising a container filled with an electrolyte solution, metal atoms that ionize in the electrolyte solution and participate in charge and discharge; and electrodes disposed in the electrolyte solution, wherein the metal atoms are configured to deposit a layer of the metal atoms on a surface of the electrode during charging; and placing the charged electricity storage device in an open-circuit state and maintaining the temperature of the electricity storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower.

[0009] In an electricity storage device to which this storage method is applied, charging is achieved by forming a layer of metal atoms involved in charging and discharging on the surface of the electrodes. According to findings obtained through original research by the inventors of the present invention, in such an electricity storage device, the higher the environmental temperature is, 25°C or higher, in an unloaded state, the more effectively self-discharge is suppressed. Furthermore, if the environmental temperature is 65°C or higher, problems such as deterioration of the electrolyte may occur. According to the storage method for an electricity storage device of the above-described form, the electricity storage device is stored in an unloaded state at an environmental temperature of 25°C or higher and 65°C or lower, thereby suppressing self-discharge and deterioration of the electricity storage device.

[0010] The present invention can be realized in various forms other than a method for storing an electricity storage device. For example, the present invention can be realized in the form of a storage system or storage device for storing an electricity storage device, or a mobile body, fixed facility, building, etc. to which the configuration of such a system or device is applied. Furthermore, in addition to a method for storing an electricity storage device, the present invention can also be realized in the form of a method for managing the temperature of an electricity storage device, a method for controlling the temperature for storing an electricity storage device, a control program for executing such a method, a recording medium on which such a program is recorded, etc. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a schematic diagram showing the configuration of a storage system according to a first embodiment. [Figure 2] 1 is a schematic diagram showing the configuration of an electricity storage device according to a first embodiment. [Figure 3] FIG. 1 is a schematic view showing the configuration of a carbon nanostructure according to a first embodiment. [Figure 4] FIG. 1 is a process flow diagram showing the steps of a method for storing an electricity storage device. [Figure 5] 4A and 4B are explanatory views showing photographed images of active material layers of an example and a comparative example. [Figure 6] FIG. 10 is a reference diagram for explaining a method for calculating a self-discharge rate SD. [Figure 7] FIG. 1 is a first explanatory diagram showing the change over time in open-circuit voltage of secondary batteries of an example and a comparative example. [Figure 8] FIG. 2 is a second explanatory diagram showing the change over time in open-circuit voltage of the secondary batteries of the example and the comparative example. [Figure 9] FIG. 3 is a third explanatory diagram showing the change over time in open-circuit voltage of secondary batteries of an example and a comparative example. [Figure 10] FIG. 10 is an explanatory diagram showing histograms of self-discharge rates for each storage temperature in an example and a comparative example. [Figure 11] FIG. 2 is an explanatory diagram showing a Cole-Cole plot obtained in the secondary battery of the example. [Figure 12] FIG. 10 is an explanatory diagram showing a Cole-Cole plot obtained in a secondary battery of a comparative example. [Figure 13] FIG. 10 is a schematic view showing the configuration of a first electrode included in an electricity storage device according to a second embodiment. [Figure 14] FIG. 10 is an explanatory diagram showing a photographed image of an example of the first electrode of the second embodiment. [Figure 15] FIG. 10 is a schematic view showing the configuration of a first electrode included in an electricity storage device according to a third embodiment. [Figure 16] FIG. 11 is an explanatory diagram showing a photographed image of an example of the first electrode of the third embodiment. [Figure 17] FIG. 10 is a schematic view showing the configuration of a first electrode of an electricity storage device according to a fourth embodiment. [Figure 18] FIG. 13 is an explanatory diagram showing a photographed image of an example of the first electrode of the fourth embodiment. [Figure 19] FIG. 11 is a schematic view showing the configuration of a first electrode included in an electricity storage device according to a fifth embodiment. [Figure 20] 13A and 13B are explanatory diagrams showing photographed images and Raman spectroscopy spectra of an example of the first electrode of the fifth embodiment. [Figure 21] FIG. 10 is a schematic diagram showing the configuration of an electricity storage device according to a sixth embodiment. [Figure 22] FIG. 13 is an explanatory view showing a photographed image of an example of the metal substrate of the sixth embodiment. [Figure 23] FIG. 13 is a schematic view showing the configuration of a metal substrate included in an electricity storage device according to a seventh embodiment. [Figure 24] FIG. 13 is an explanatory view showing a photographed image of an example of the metal substrate of the seventh embodiment. [Figure 25] FIG. 13 is a schematic diagram showing the configuration of an electricity storage device according to an eighth embodiment. [Figure 26] FIG. 13 is an explanatory diagram showing an example of change in X-ray diffraction due to heat treatment of the metal substrate of the eighth embodiment. [Figure 27] FIG. 13 is an explanatory diagram showing an example of a change in a two-dimensional diffraction image of Debye rings due to heat treatment of the metal substrate of the eighth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of a method for storing an electricity storage device and a system for storing an electricity storage device according to the present invention will be described with reference to the drawings.

[0013] 1. First embodiment: 1-1. Storage system configuration: 1 is a schematic diagram showing the configuration of a storage system 100 for an electricity storage device 10 according to a first embodiment. The electricity storage device 10 to be stored in the storage system 100 of this embodiment is a lithium ion battery that is charged by an electrode reaction different from intercalation. The configuration of the electricity storage device 10 and the electrode reaction in the electricity storage device 10 will be described later.

[0014] The storage system 100 can store the charged electricity storage device 10 in a state where self-discharge is suppressed and deterioration of internal chemical substances is suppressed. The storage system 100 includes a storage unit 101 that stores the electricity storage device 10, a temperature monitoring unit 102 that monitors the temperature of the electricity storage device 10 stored in the storage unit 101, and a temperature control unit 103 that adjusts the temperature inside the storage unit 101. The storage system 100 also includes a control unit 105 that controls the storage system 100.

[0015] The storage unit 101 has an airtight internal space in which the power storage devices 10 are stored. The storage unit 101 can store one or more power storage devices 10. The storage unit 101 may be provided with shelves or the like for placing the power storage devices 10 thereon.

[0016] The internal space of the storage unit 101 is preferably insulated from the external environment. Therefore, the outer wall section that partitions the internal space of the storage unit 101 is preferably made of a material with high thermal insulation properties. The outer wall section may have a configuration in which a thermal insulation layer is provided inside.

[0017] In this embodiment, after the power storage device 10 is charged, the terminals are opened and the electrical connection is cut off, and the power storage device 10 is stored in the storage unit 101 in an unloaded open-circuit state. In the storage unit 101, the power storage device 10 may be stored in a state electrically connected to an electric circuit that monitors the state of charge (SOC) of the power storage device 10, a charging device that can charge the power storage device 10, or the like.

[0018] The temperature monitoring unit 102 includes, for example, a temperature sensor, and outputs a signal representing the temperature of the power storage device 10 stored in the storage unit 101 to the control unit 105. In this embodiment, the temperature monitoring unit 102 measures the environmental temperature inside the storage unit 101, which directly affects the temperature of the power storage device 10, as a temperature representing the temperature of the power storage device 10, and outputs the measured temperature to the control unit 105.

[0019] In another embodiment, the temperature monitoring unit 102 may be configured to directly measure the temperature of each power storage device 10 housed in the storage unit 101. In another embodiment, the temperature monitoring unit 102 may be configured to measure the air temperature outside the storage unit 101 and calculate an estimated value of the environmental temperature inside the storage unit 101 from that temperature.

[0020] The temperature control unit 103 is provided in the storage unit 101, and adjusts the temperature of the power storage device 10 housed in the storage unit 101 under the control of the control unit 105. In this embodiment, the temperature control unit 103 is configured by a heater and an air conditioner, and adjusts the environmental temperature inside the storage unit 101.

[0021] In another embodiment, the temperature control unit 103 may adjust the temperature of the electricity storage device 10 by heating or cooling the electricity storage device 10 stored in the storage unit 101. For example, the temperature control unit 103 may adjust the temperature of the electricity storage device 10 by supplying a refrigerant whose temperature has been adjusted to a refrigerant flow path provided inside a jacket that covers the electricity storage device 10. The temperature control unit 103 may also adjust the temperature of the electricity storage device 10 by using a heater element or Peltier element attached to the electricity storage device 10.

[0022] The control unit 105 is configured by, for example, a microcomputer including a central processing unit (CPU) and a main memory device (RAM). The control unit 105 drives the temperature control unit 103 based on the measurement results by the temperature monitoring unit 102 to adjust the temperature of the power storage device 10 stored in the storage unit 101. In this embodiment, the control unit 105 maintains the temperature of the power storage device 10 at a predetermined storage temperature of 25°C or higher and 65°C or lower. The temperature range of the storage temperature will be described in detail later.

[0023] 1-2. Configuration of the energy storage device: 2 is a schematic diagram showing the configuration of an electricity storage device 10 according to the first embodiment. In this embodiment, the electricity storage device 10 is a lithium ion battery as described above, and therefore includes lithium (Li) atoms as metal atoms that are ionized in an electrolytic solution and participate in charging and discharging.

[0024] The electricity storage device 10 includes a container 11, an electrolyte solution 12, a separator 15, a first electrode 20, and a second electrode 30. For convenience, in Fig. 2, the container 11 is shown by a dashed line, and the separator 15 is shown by a broken line.

[0025] The container 11 has an internal space filled with the electrolytic solution 12. The container 11 is liquid-tight and made of a material that is not easily reactive with the electrolytic solution 12. The electrolytic solution 12 has the property of being able to transfer metal ions involved in charge and discharge between the first electrode 20 and the second electrode 30. In this embodiment, the electrolytic solution 12 is made of a solution in which a lithium salt is dissolved in an organic solvent, and is able to transfer Li ions between the first electrode 20 and the second electrode 30.

[0026] The lithium salt of the electrolyte 12 is, for example, LiN(SO2R A )(SO2R B ) can be used. A " and "R B " represents a fluorine atom (F) or a fluorocarbon, respectively. "R A " and "R B " may be the same atom or a group having the same structure. In the electrolyte solution 12 of this embodiment, lithium bis(fluorosulfonyl)imide (LiN(FSO2)2, LiFSI), which is a lithium imide salt, is used as the lithium salt.

[0027] Other examples of the lithium salt that can be used include lithium imide salts such as lithium bis(trifluoromethanesulfonyl)imide (LiN(CF3SO2)2, LiTFSI), lithium bis(perfluoroethylsulfonyl)imide (LiN(SO2C2F5)2, LiBETI), and CTFSI-Li. The lithium salt is not limited to lithium imide salts, and for example, lithium hexafluorophosphate (LiPF6) can also be used. The lithium salt may be a derivative of any of the lithium salts described above, or a mixture of any combination of the lithium salts described above or their derivatives.

[0028] In this embodiment, the organic solvent of the electrolytic solution 12 is 1,2-dimethoxyethane (DME, CH 10Other organic solvents for the electrolyte 12 include, for example, 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE, CHF0) and 1,2-diethoxyethane (DEE, CH 14 O2), triglyme (triglyme, CH3OCH2CH2OCH2CH2OCH2CH2OCH3), tetraglyme (dimethoxytetraethylene glycol tetraglyme, C 10 H 22 Examples of organic solvents that can be used include ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl) ether (BTFE), and tris[(trifluoroethoxy)methane] (TFEO). The organic solvent may be a derivative of any of the above-mentioned substances, or a mixture of any combination of the above-mentioned substances and their derivatives.

[0029] An additive may be further added to the electrolytic solution 12. Examples of the additive include vinylene carbonate (VC), lithium nitrate (LiNO), boroxine compounds including triisopropoxyboroxine (TiPBx), derivatives thereof, and mixtures of any combinations thereof. The additive may be added to the electrolytic solution 12 at a concentration of 0.1% by mass or more and 2.0% by mass or less, for example.

[0030] The separator 15 divides the internal space of the container 11 into a first electrode chamber 16 that houses the first electrode 20 and a second electrode chamber 17 that houses the second electrode 30. The separator 15 is electrically insulating and ion conductive, and electrically insulates the first electrode 20 from the second electrode 30 while allowing metal ions (Li ions in this embodiment) transmitted via the electrolyte 12 to pass through. The separator 15 is made of, for example, a resin film or nonwoven fabric having a porous structure.

[0031] The first electrode 20 constitutes a negative electrode. The first electrode 20 includes a current collector 21 and an active material layer 25. The current collector 21 of the first electrode 20 is formed of a metal substrate 23. In this embodiment, the metal substrate 23 has a smooth surface.

[0032] In this embodiment, the metal substrate 23 is made of a metal foil of copper (Cu). The metal substrate 23 may be made of Cu, a Cu alloy, or a metal other than Cu. The metal substrate 23 may be made of, for example, aluminum (Al) or an Al alloy.

[0033] The metal substrate 23 does not have to be made of metal foil, but may be made of, for example, a metal sheet or a metal film. The metal substrate 23 does not have to be configured in a flat plate shape, but may be bent into various shapes, such as a cylindrical shape or a corrugated shape.

[0034] The active material layer 25 of the first electrode 20 is provided on the plate surface of the metal substrate 23. The active material layer 25 is preferably provided on both surfaces of the metal substrate 23. The active material layer 25 contains carbon (C) as an active material and is conductive. In this embodiment, the active material layer 25 contains carbon nanostructures CN. The carbon nanostructures CN will be described in detail later.

[0035] The second electrode 30 constitutes the positive electrode of the electricity storage device 10. The second electrode 30 has a current collector 31 and an active material layer 35. The current collector 31 is made of, for example, a metal foil such as Al or titanium (Ti). The current collector 31 may be made of another metal or may have a form other than a metal foil. The current collector 31 does not have to be configured in a flat shape, and may be bent into various shapes such as a cylindrical shape or a corrugated shape.

[0036] The active material layer 35 of the second electrode 30 is formed on the surface of the current collector 31. The active material layer 35 is preferably formed on both sides of the current collector 31. The active material layer 35 contains an active material including metal ion atoms (Li atoms in this embodiment) involved in charge and discharge, a conductive additive, and a binder. The active material layer 35 may also contain a thickener.

[0037] The active material of the second electrode 30 may be, for example, a ternary material, such as lithium cobalt oxide (LiCoO2, LCO), lithium manganese oxide (LMO), or lithium nickel oxide (NCA). The conductive additive may be, for example, acetylene black, carbon black (CB), carbon nanotubes (CNT), acetylene black (AB), or a mixture thereof. The binder may be, for example, polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR). The thickener may be, for example, carboxymethyl cellulose (CMC).

[0038] Fig. 3 is a schematic diagram showing the configuration of the carbon nanostructure CN included in the active material layer 25 of the first electrode 20. For convenience, in Fig. 3, graphene GF constituting the carbon nanostructure CN is shown in the form of a substantially rectangular sheet.

[0039] Graphene GF as a main component and carbon nanostructures CN are arranged all over the surface of the metal substrate 23 of the first electrode 20. Graphene GF, also known as a "graphene sheet," is a sheet-like material with a thickness equivalent to one carbon atom, composed of a six-membered carbon ring structure, i.e., a hexagonal lattice structure with carbon atoms at the vertices. Carbon nanostructures CN are graphite-like materials and therefore have higher electrical conductivity than carbon materials such as activated carbon.

[0040] In this embodiment, the carbon nanostructure CN has a configuration in which graphene GF extends elongatedly with its base end facing the metal substrate 23. The carbon nanostructure CN has a multilayer structure in which a plurality of graphene GF are stacked in the thickness direction.

[0041] Graphene GF does not have to be entirely composed of single crystals of six-membered carbon rings. In other words, graphene GF may not have a complete graphene structure, but may be a thin film mainly composed of carbon with a six-membered ring structure. Graphene GF may have a mosaic structure mainly composed of carbon with a six-membered ring structure. The mosaic structure refers to a structure in which multiple regions composed of six-membered carbon ring structures are discretely arranged.

[0042] The carbon nanostructures CN can be produced by a known chemical vapor deposition (CVD) method on the surface of the metal substrate 23. The CVD method capable of producing the carbon nanostructures CN is described in, for example, Japanese Patent Application Laid-Open No. 2024-016510.

[0043] Although not shown in the figure, the surface of the metal substrate 23 is covered with an amorphous carbon layer. In the CVD method, after an amorphous carbon layer is formed on the surface of the metal substrate 23, carbon nanostructures CN are formed so as to extend upward in elongated shapes, with the amorphous carbon layer serving as the starting point for growth.

[0044] In this embodiment, the carbon nanostructure CN is composed of carbon nanowalls extending from the smooth plate surface of the metal substrate 23. The carbon nanowalls have a configuration in which graphene GF is stacked in the thickness direction.

[0045] Carbon nanowalls may be formed in the shape of needles, plates, or pleats. In this specification, the term "carbon nanowall" is used to broadly encompass not only wall-like structures connected in a strip shape, but also similar structures mainly composed of graphene, such as so-called carbon nanoflakes and carbon nanoflowers.

[0046] 1-3. Battery reaction in energy storage devices: The electricity storage device 10 is configured so that, during charging, metal atoms involved in charging and discharging are deposited on the surface of the first electrode 20 to form a layer of the metal atoms. The electrode reaction during charging and discharging of the electricity storage device 10 of this embodiment, which is a lithium ion battery, can be expressed, for example, by the following reaction formula.

[0047] When the positive electrode material is LiCoO2, the electrode reaction at the second electrode 30, which is the positive electrode, is expressed by the following chemical formula (1): x represents the proportion of reacting atoms and is a real number greater than 0 and less than 1.

[0048] [C1] Li 1-x CoO2+ xLi + + xe - ⇔ LiCoO2…(1)

[0049] In contrast, the electrode reaction at the first electrode 20, which is the negative electrode, is expressed by the following chemical formula (2): As shown in chemical formula (2), when the electricity storage device 10 is charged, Li is deposited on the surface of the first electrode 20, and a Li layer is formed.

[0050] [Case 2] Li + + e - ⇔ Li …(2)

[0051] Generally, the charge capacity of conventional lithium-ion batteries, which are charged by intercalation, in which metal ions involved in charging and discharging are inserted into gaps in the crystalline structure of the electrodes, is limited by the crystalline structure of the electrodes. In contrast, with the electricity storage device 10 of this embodiment, as shown in the above chemical formula (2), theoretically, charging is possible as long as Li can be deposited on the surface of the first electrode 20. Therefore, with the electricity storage device 10 of this embodiment, a higher charge capacity can be achieved than with electricity storage devices in which intercalation occurs in the electrodes during charging.

[0052] Furthermore, as will be described later, the energy storage device 10 of this embodiment, which is charged by the above-mentioned electrode reaction, can effectively suppress self-discharge when stored at a storage temperature of 25°C or higher, unlike conventional lithium-ion batteries.

[0053] 1-4.Storage method for energy storage devices: A method for storing the electricity storage device 10 using the storage system 100 will be described with reference to FIG.

[0054] In step 1, the stored electricity storage device 10 is charged. In this embodiment, the electricity storage device 10 is fully charged. The electricity storage device 10 is preferably charged in a room temperature environment of, for example, 18°C ​​or higher and lower than 35°C, and more preferably charged at an ambient temperature of 25°C.

[0055] In step 2, the charged electricity storage device 10 is stored in the storage section 101 of the storage system 100. After storing the electricity storage device 10, the storage section 101 is preferably sealed.

[0056] In step 3, the temperature of the electricity storage device 10 housed in the storage unit 101 is maintained at a predetermined storage temperature under the control of the control unit 105. In this embodiment, the temperature control unit 103 adjusts the environmental temperature of the storage unit 101, thereby maintaining the electricity storage device 10 at the storage temperature. The storage temperature is, for example, a value of 25°C or higher and 65°C or lower.

[0057] As will be shown in experimental examples described later, the self-discharge of the electricity storage device 10 of this embodiment is suppressed more at temperatures of 25°C or higher than at temperatures of 0°C or lower. Furthermore, as will be shown in experimental examples, the higher the storage temperature, the more the self-discharge of the electricity storage device 10 is suppressed. Therefore, the storage temperature is preferably 30°C or higher, and more preferably room temperature or higher. Here, "room temperature" means, for example, a temperature of 18°C ​​or higher and lower than 35°C. The storage temperature is more preferably 35°C or higher, and even more preferably 38°C or higher. The storage temperature is even more preferably 40°C or higher.

[0058] In general, in energy storage devices that achieve charging through intercalation at electrodes, such as conventional lithium-ion batteries, when the ambient temperature rises above room temperature, the release of metal ions from the electrodes is promoted, and the self-discharge rate tends to increase. For example, in high-temperature environments such as summer, where the temperature is 35°C or higher, it is known that more than 45% of the stored energy can be lost due to self-discharge. Furthermore, conventional energy storage devices are known to deteriorate significantly when stored at ambient temperatures above 40°C.

[0059] For this reason, some electric vehicles equipped with conventional power storage devices employ a configuration in which the power storage device is cooled by a cooling means such as a fan, etc. However, in such a configuration, for example, in summer, in order to cool the conventional power storage device to a temperature at which self-discharge and degradation of the device can be suppressed, for example, 35°C or less, the amount of power consumed for cooling may increase significantly, making it inefficient.

[0060] In contrast, in a configuration in which a layer of metal atoms involved in charging and discharging is formed on the surface of the first electrode 20 during charging, as in the electricity storage device 10 of this embodiment, the metal atoms precipitated on the first electrode 20 can remain stable on the electrode. Therefore, with the electricity storage device 10 of this embodiment, self-discharge and deterioration are suppressed even in high-temperature environments of 25°C or higher, 30°C or higher, or 35°C or higher. While the conventional electricity storage devices described above are expected to be stored at temperatures of 35°C or lower, with the electricity storage device 10 of this embodiment, self-discharge and deterioration are suppressed even in an environmental temperature of 50°C without cooling.

[0061] Therefore, the electricity storage device 10 of this embodiment can achieve the above-mentioned high storage temperature. Achieving a high storage temperature means that the amount of storage temperature adjustment can be reduced, even in an environment where the outside air temperature is high, such as in summer. Therefore, an increase in energy consumption for adjusting the storage temperature of the electricity storage device 10 can be suppressed, which is efficient.

[0062] In the electricity storage device 10 of this embodiment, if the storage temperature exceeds 65°C, the electrolyte solution 12 may begin to deteriorate. Therefore, in this embodiment, the storage temperature is set to 65°C or lower. In order to more reliably suppress deterioration of the electrolyte solution 12, the storage temperature is preferably 50°C or lower. From the viewpoint of more reliably suppressing deterioration of the electrolyte solution 12 and suppressing energy consumption for temperature adjustment by the temperature control unit 103, the storage temperature is more preferably 45°C or lower.

[0063] When the electricity storage device 10 is to be used, it is removed from the storage unit 101 (step 4). As described above, in the storage system 100, the storage unit 101 is maintained at a predetermined storage temperature, so that the electricity storage device 10 is prevented from self-discharging or deteriorating, and a good state of charge is maintained even after a long storage period, so that it can be used quickly and smoothly.

[0064] 1-5. Experimental example on self-discharge of energy storage devices: An experimental example verifying the self-discharge suppression effects of an electricity storage device E1 as an example and an electricity storage device C1 as a comparative example will be described with reference to FIGS. 5 to 12 in this order.

[0065] (1) Energy storage device in this experimental example: The electricity storage device E1 of the example was fabricated as a lithium ion battery coin cell having the configuration shown in the following Table 1. The electricity storage device C1 of the comparative example was fabricated to have substantially the same configuration as the electricity storage device E1 of the example, except that the configuration of the active material layer of the negative electrode, which is the first electrode, was different.

[0066] [Table 1]

[0067] The upper part of Fig. 5 shows photographed images I1a and I1b showing the active material layer of an electricity storage device E1 produced as an example of this embodiment. Photographed image I1a of example E1 is an image obtained by viewing the active material layer with a scanning electron microscope in a direction perpendicular to the thickness direction of the metal substrate of the electrode. Photographed image I1b of the example is an image obtained by viewing the active material layer with a scanning electron microscope in the thickness direction of the metal substrate of the electrode.

[0068] A photographed image I1c showing the active material layer of an electricity storage device C1 produced as a comparative example is shown in the lower part of Figure 5. The photographed image I1c of the comparative example is an image of the active material layer viewed with a scanning electron microscope in the thickness direction of the metal substrate of the electrode.

[0069] As shown in Table 1 and photographed images I1a and I1b, the active material layer of the example electricity storage device E1 was composed of carbon nanowalls. These carbon nanowalls were formed on the smooth surface of Cu foil, the metal substrate constituting the current collector, by a CVD method under the conditions shown in Table 2 below. In this CVD method, hydrogen was plasma-treated using a microwave power source. The "pressure" in Table 2 is the pressure inside the treatment chamber. Furthermore, the "heating temperature" in Table 2 is the temperature of the metal substrate measured with a thermocouple. The flow rate unit "sccm" in this specification may be converted to 1 mL / min.

[0070] [Table 2]

[0071] The carbon nanowalls constituting the negative electrode active material layer of the example power storage device E1 were formed with a substantially uniform height of about 1.0 μm. In the example power storage device E1, it was confirmed that during charging, a layer of Li atoms was formed on the surface layer of the first electrode due to the electrode reaction represented by the above chemical formula (2).

[0072] See image I1c. In the comparative example of power storage device C1, the negative electrode active material layer was formed as a graphite layer in which graphite particles were spread on the smooth surface of Cu foil. In the case of the negative electrode configuration of the comparative example of power storage device C1, charging occurs by intercarnation, in which Li ions are inserted into the gaps in the crystalline structure of the graphite in the negative electrode.

[0073] (2) Self-discharge rate by storage temperature: A method for calculating the self-discharge rate SD, which is an index showing the self-discharge suppression performance of an electricity storage device in this experimental example, will be described with reference to Fig. 6. Fig. 6 shows an example of the change over time in open-circuit voltage when a charged electricity storage device is kept in an open-circuit state and at a constant storage temperature.

[0074] The lower the self-discharge rate SD, the more suppressed the self-discharge of the power storage device is. To calculate the self-discharge rate SD, first, a fully charged power storage device is placed in an open-circuit state with electrical connections cut off, and stored for a specified period of time in an environment maintained at a constant humidity and constant storage temperature. Next, the initial open-circuit voltage V0 of the power storage device and the open-circuit voltage V1 of the secondary battery after the storage period have elapsed are determined, and the self-discharge rate SD [%] of the secondary battery is calculated using the following formula (A). Note that ΔV in Figure 6 represents the amount of voltage drop due to self-discharge and is the value obtained by subtracting V1 from V0.

[0075] [Number 1] SD[%]=(V0-V1) / V0×100 …(A)

[0076] In this experimental example, the electricity storage device E1 of the example and the electricity storage device C1 of the comparative example, which were in a fully charged state, were placed in an airtight storage compartment of an environmental tester (SH-242 manufactured by Espec Corporation) in an open-circuit state for three days (approximately 72 hours), and the change in open-circuit voltage over time was measured while the temperature inside the storage compartment was kept constant at either 40° C., 25° C., or −10° C. In both cases, the humidity inside the storage compartment was kept at 50% RH.

[0077] 7, 8, and 9 are graphs showing the changes over time in the open-circuit voltage of electricity storage devices E1 and C1 stored in a storage facility at storage temperatures of 40°C, 25°C, and -10°C, respectively. The solid-line graphs G1, G2, and G3 in FIGS. 7, 8, and 9 show the open-circuit voltage of electricity storage device E1 of the example, and the dashed-dash line graphs G1a, G2a, and G3a show the open-circuit voltage of electricity storage device C1 of the comparative example. Table 3 below summarizes the ΔV and self-discharge rate SD obtained for storage temperatures of 40°C, 25°C, and -10°C.

[0078] [Table 3]

[0079] As shown in FIG. 7, at a storage temperature of 40°C, the open-circuit voltage of the comparative power storage device C1 dropped sharply within a few hours after being stored in a storage facility. As a result, the voltage drop ΔV of the comparative power storage device C1 was approximately 0.19 V, and the self-discharge rate SD was approximately 45%. In contrast, the open-circuit voltage of the example power storage device E1 was maintained approximately constant during the storage period. As a result, the voltage drop ΔV of the example power storage device E1 was approximately 0.022 V, and the self-discharge rate SD was approximately 0.14%.

[0080] As shown in Fig. 8, at a storage temperature of 25°C, the decrease in open-circuit voltage was suppressed in almost the same manner during the storage time for both the power storage device C1 of the comparative example and the power storage device E1 of the example. However, the open-circuit voltage of the power storage device E1 of the example was always higher than that of the power storage device C1 of the comparative example, and the difference was significantly large. The voltage drop ΔV for the power storage device C1 of the comparative example was approximately 0.02 V, and the self-discharge rate SD was approximately 0.5%. The voltage drop ΔV for the power storage device E1 of the example was approximately 0.022 V, and the self-discharge rate SD was approximately 0.5%.

[0081] As shown in Fig. 9, at a storage temperature of -10°C, the amount of voltage drop ΔV was smaller for the power storage device E1 of the example than for the open-circuit voltage of the power storage device C1 of the comparative example. Furthermore, the open-circuit voltage of the power storage device C1 of the comparative example dropped sharply around 20 hours after storage, whereas the open-circuit voltage of the power storage device E1 of the example dropped gradually at a substantially constant rate. The amount of voltage drop ΔV for the power storage device C1 of the comparative example was approximately 0.13 V, and the self-discharge rate SD was approximately 3.1%. The amount of voltage drop ΔV for the power storage device E1 of the example was approximately 0.009 V, and the self-discharge rate SD was approximately 2.2%.

[0082] FIG. 10 shows a histogram comparing the self-discharge rates SD obtained for the electricity storage device E1 of the example and the electricity storage device C1 of the comparative example at storage temperatures of 40°C, 25°C, and -10°C.

[0083] The power storage device C1 of the comparative example had a self-discharge rate SD that was approximately equal to that of the power storage device E1 of the example at a storage temperature of 25° C. However, at a storage temperature of −10° C., the self-discharge rate SD of the power storage device C1 of the comparative example was higher than that of the power storage device E1 of the example. Furthermore, at a storage temperature of 40° C., the self-discharge rate SD of the power storage device C1 of the comparative example was much higher than that of the power storage device E1 of the example, and the open-circuit voltage was reduced to nearly half.

[0084] In contrast, in the electricity storage device E1 of the example, the self-discharge rate SD was kept to a value of less than 2.5% over the range of -10°C to 40°C. Furthermore, in the electricity storage device E1 of the example, the self-discharge rate SD decreased as the storage temperature increased. In the electricity storage device E1 of the example, the self-discharge rate SD was 0.5% or less at a storage temperature of 25°C or higher, and the self-discharge rate SD decreased to the 0.1% range at a storage temperature of 40°C.

[0085] Thus, the difference in self-discharge between the electricity storage device E1 of the example and the electricity storage device C1 of the comparative example became significantly large at a storage temperature of 40° C. Below, the difference between the electricity storage device E1 of the example and the electricity storage device C1 of the comparative example at a storage temperature of 40° C. was verified using an AC impedance method.

[0086] (3) Analysis by AC impedance method: Fig. 11 shows a Cole-Cole plot obtained by AC impedance spectroscopy for the electricity storage device E1 of the example. Fig. 12 shows a Cole-Cole plot obtained by AC impedance spectroscopy for the electricity storage device C1 of the comparative example.

[0087] 11 and 12, the graphs for the initial state when the fully charged power storage devices E1 and C1 are in an open-circuit state and storage at a storage temperature of 40°C is started are shown by dashed lines, and the graphs for three days after the start of storage are shown by solid lines. Total ,W Warburg is shown against the solid line graph after three days have passed.

[0088] Table 4 below lists the resistances Rs, Rp, Rn, and R obtained in the Cole-Cole plots shown in Figures 11 and 12. Total and Warburg impedance W Warburg The values ​​of are summarized.

[0089] [Table 4]

[0090] As shown in FIG. 11 and Table 4, in the electricity storage device E1 of the example, the resistance Rs did not change during the storage period of 3 days, and the electrode resistance Rp of the positive electrode did not change much. In the electricity storage device E1 of the example, the Warburg impedance W Warburg The total resistance R Total also decreased.

[0091] On the other hand, as shown in FIG. 12 and Table 4, in the comparative example of the electricity storage device C1, the resistance Rs increased slightly, the electrode resistance Rp at the positive electrode increased significantly, and the resistance Rn also increased, and the Warburg impedance W Warburg As a result, in the comparative example of the electricity storage device C1, the total resistance R Total increased significantly.

[0092] In this way, in the electricity storage device E1 of the example, the Warburg impedance W Warburg and total resistance R Total From this, it is presumed that the reason why the self-discharge rate SD of the electricity storage device E1 of the example was kept low at a storage temperature of 40°C is that the Li atoms deposited on the surface of the negative electrode by the chemical reaction of charging formed a metal layer and continued to exist on the surface of the negative electrode in a stable state.

[0093] On the other hand, in the comparative example of the electricity storage device C1, the Warburg impedance W Warburg and total resistance R Total This suggests that the reason why the self-discharge rate SD of the comparative electricity storage device C1 at a storage temperature of 40°C increased significantly is because the release of Li ions that had entered the crystalline structure of the graphite in the negative electrode by intercalation was promoted in a high-temperature environment.

[0094] (4) Summary of the experimental example: As described above, in the electricity storage device C1 of the comparative example, the self-discharge rate SD was lowest at 25°C and increased rapidly at 40°C, indicating that a storage temperature of 25°C or less tends to be suitable for the electricity storage device C1 of the comparative example. In contrast, in the electricity storage device E1 of the example, the self-discharge rate SD decreased as the storage temperature increased within the temperature range of -10°C to 40°C. From these results, it can be seen that for the electricity storage device E1 of the example, the higher the storage temperature, the more effectively self-discharge can be suppressed, and that a storage temperature of 25°C or higher can more effectively suppress self-discharge.

[0095] 1-6. Summary of the first embodiment: As described above, according to the storage system 100 and storage method for the electricity storage device 10 of the first embodiment, the electricity storage device 10 is stored at a storage temperature of 25°C or higher and 65°C or lower, which is suitable for the electricity storage device 10, and therefore self-discharge of the electricity storage device 10 can be effectively suppressed. This makes it possible to achieve highly efficient power utilization in the electricity storage device 10. Furthermore, deterioration of the electricity storage device 10 due to being placed in a high-temperature environment can also be suppressed.

[0096] 2. Second embodiment: Fig. 13 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20A included in an electricity storage device 10A that is a storage target in the storage system and storage method of Embodiment 2. Fig. 13 illustrates a cross-sectional structure of the first electrode 20A at an arbitrary cut surface along the thickness direction.

[0097] The storage system and storage method of the second embodiment are the same as those described in the first embodiment (FIGS. 1 and 4), except that the configuration of the electricity storage device 10A to be stored is different. The electricity storage device 10A of the second embodiment has almost the same configuration as the electricity storage device 10 of the first embodiment, except that the configuration of the first electrode 20A is different.

[0098] The first electrode 20A of the power storage device 10A has a configuration in which an active material layer 25A is formed on the surface of a metal substrate 23A. The surface of the first electrode 20A has a fine uneven structure in which a plurality of minute particles 40 that make up the active material layer 25A are densely arranged. Each particle 40 of the first electrode 20A has a particle-like outer periphery when viewed in the thickness direction of the metal substrate 23A.

[0099] In this specification, the term "granular material" refers to a portion that can be recognized as having a particle-like shape when viewed from a certain direction, and is a concept that includes protruding portions that are approximately spherical. Also, in this specification, the term "particle" refers to a concept that means minute lumps of various shapes, which do not necessarily have an approximately spherical shape, and is a concept that includes shapes that have a random uneven structure on the surface.

[0100] Carbon nanostructures CNa are formed all over the surface layer of the granules 40. The carbon nanostructures CNa are made of graphene GF as described in FIG. 3, and extend thinly outward from the granules 40. The carbon nanostructures CNa extend from an amorphous carbon layer AC that covers the surface of a particle structure 41, which is a densely formed protrusion on the surface of the metal substrate 23A. The particle structure 41 of the metal substrate 23A has a configuration in which minute metal particles MP are gathered in clusters.

[0101] A method for forming the granular material 40 of the first electrode 20A is described in detail in Japanese Patent Application Laid-Open No. 2024-16510. The granular material 40 of the first electrode 20A is formed by forming a particle structure 41 on the surface of the metal substrate 23A and then generating carbon nanostructures CNa on the surface of the particle structure 41.

[0102] The particle structure 41 of the metal substrate 23A is formed by performing a surface treatment on the base material of the metal substrate 23A, which has a smooth surface. The surface treatment is, for example, electrolytic deposition. The particle structure 41 is formed by immersing the base material of the metal substrate 23A and an electrode plate in an electrolyte, and applying a voltage with the electrode plate as the anode and the base material of the metal substrate 23A as the cathode, thereby precipitating metal ions contained in the electrode plate onto the surface of the base material of the metal substrate 23A.

[0103] The carbon nanostructures CNa are formed by a plasma treatment using a CVD method on the surface of the metal substrate 23A on which the particle structures 41 are formed. In this plasma treatment, a carbon-based gas containing carbon and a reaction contributing gas such as hydrogen (H2) or argon (Ar) are used as raw material gases.

[0104] In the plasma treatment, the metal substrate 23A is placed in a reaction chamber, and while the metal substrate 23A is heated to a temperature of 700°C or less using a heater, a raw material gas is supplied and a high-frequency voltage is applied between the metal substrate 23A and an electrode in the reaction chamber. This generates a high-density capacitively coupled plasma in the reaction chamber, and the radicals generated in the plasma form carbon nanostructures CNa on the surface of the metal substrate 23A.

[0105] The electricity storage device 10A of the second embodiment has the first electrode 20A configured as described above, and is therefore capable of charging and discharging by the electrode reactions of the chemical formulas (1) and (2) described in the first embodiment. When the electricity storage device 10A is charged, Li, which is involved in charging and discharging, precipitates and forms a layer of Li on the granules 40 of the first electrode 20.

[0106] The average particle size of the granules 40 in the first electrode 20A is preferably 0.1 μm or more and 10.0 μm or less, more preferably 0.5 μm or more and 5.0 μm or less, and even more preferably 1.0 μm or more and 3.0 μm or less. By setting the average particle size of the granules 40 within this preferred range, deposition of metal atoms involved in charging and discharging onto the surface of the first electrode 20A during charging of the electricity storage device 10A is facilitated, and the generation of dendrites can be suppressed.

[0107] 14 shows captured images I2a, I2b, I2c, and I2d illustrating an example of the first electrode 20A of the second embodiment. The captured images I2a and I2c were taken in a direction perpendicular to the thickness direction of the metal substrate 23A, and the captured images I2b and I2d were taken in the thickness direction of the metal substrate 23A.

[0108] The captured images I2a and I2b show the surface of the metal substrate 23A before the carbon nanostructures CNa are formed. In this example, the metal substrate 23A in the captured images I2a and I2b is a Cu foil. An uneven structure was formed on the surface of the metal substrate 23A, in which particle structures 41, each of which is composed of metal particles MP gathered in a tuft-like shape, were densely arranged.

[0109] The captured images I2c and I2d show granules 40 having carbon nanostructures CNa formed on the surface of particle structure 41. Table 5 below shows the processing conditions for the plasma processing that formed the carbon nanostructures CNa in the captured images I2c and I2d.

[0110] [Table 5]

[0111] A lithium-ion battery coin cell was fabricated using the active material layer 25A shown in photographed images I2c and I2d under the conditions of Table 1 described in the first embodiment. During charging, the lithium-ion battery formed a layer of Li on the granules 40 of the first electrode 20A due to the electrode reaction of chemical formula (2) described in the first embodiment.

[0112] The electricity storage device 10A of the second embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a temperature suitable for storage at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Therefore, even with the electricity storage device 10A of the second embodiment, self-discharge and performance degradation can be suppressed by storing the electricity storage device 10A in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the second embodiment can achieve various effects similar to those described in the first embodiment.

[0113] 3. Third embodiment: Fig. 15 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20B included in an electricity storage device 10B that is a storage target in the storage system and storage method of Embodiment 3. Fig. 15 illustrates a cross-sectional structure of the first electrode 20B in an arbitrary cross section along the thickness direction.

[0114] The storage system and storage method of the third embodiment are the same as those described in the first embodiment (FIGS. 1 and 4), except that the configuration of the electricity storage device 10B to be stored is different. The electricity storage device 10B of the third embodiment has almost the same configuration as the electricity storage device 10 of the first embodiment, except that the configuration of the active material layer 25B of the first electrode 20B is different.

[0115] The active material layer 25B of the first electrode 20B of the third embodiment has an amorphous carbon layer AC covering the surface of the metal substrate 23B and carbon nanostructures CNb formed on the amorphous carbon layer AC. The amorphous carbon layer AC is a thin film layer made of carbon and is the starting point for the growth of the carbon nanostructures CNb. The formation of the amorphous carbon layer AC is favorable, improving the state of formation of the carbon nanostructures CNb.

[0116] The carbon nanostructures CNb of the third embodiment are minute structures made entirely of carbon, and are formed so as to be distributed over the entire surface of the amorphous carbon layer AC. Because the carbon nanostructures CNb are graphite-like substances, they have higher electrical conductivity than carbon materials such as activated carbon.

[0117] The carbon nanostructure CNb has a base portion 43 that extends elongatedly in the thickness direction of the metal substrate 23B, and a plurality of extension portions 44 that extend from the base portion 43. Most of the plurality of extension portions 44 are formed so as to branch out in a branch-like manner on the upper end side of the base portion 43.

[0118] As will be shown in a photographed image later, the base 43 is arranged in a random mesh pattern on the surface of the metal substrate 23B. The base 43 has a multilayer structure in which a plurality of graphene GFs, as described in FIG. 3, are stacked in the thickness direction. The number of stacked graphene GFs in the base 43 varies. The base 43 is formed in a needle, plate, or pleat shape. The base 43 can also be interpreted as a structure similar to a carbon nanowall.

[0119] Each extension 44 is made of carbon and is formed in a needle, column, plate, or pleat shape. Most of the extensions 44 are randomly distributed on the surface of the upper end of the base 43. By forming each extension 44 on the base 43, the gaps between the carbon nanostructures CNb near the surface of the active material layer 25 are reduced.

[0120] The height of the carbon nanostructure CNb corresponds to the height from the lower end of the base 43 on the metal substrate 23B side to the upper end of the extension 44. The height of the carbon nanostructure CNb is preferably 0.5 μm or more, and more preferably 0.8 μm or more. Furthermore, the height of the carbon nanostructure CNb is further preferably 1.0 μm or more, and even more preferably 1.2 μm or more.

[0121] However, the taller the carbon nanostructures CNb, the longer the time required to form them. Therefore, from the viewpoint of improving the productivity of the electrode 20, it is preferable that the average height of the carbon nanostructures CNb be 10.0 μm or less. It is more preferable that the average height of the carbon nanostructures CNb be 8.0 μm or less, and even more preferable that the average height be 5.0 μm or less. It is even more preferable that the average height of the carbon nanostructures CNb be 3.0 μm or less.

[0122] Details of the method for manufacturing the carbon nanostructures CNb constituting the active material layer 25B of the third embodiment are disclosed in the specification of Japanese Patent Application No. 2022-212870. The carbon nanostructures CNb of the third embodiment are formed by two types of CVD methods. These two types of CVD methods are the radical-injection plasma-enhanced (RI-PE) CVD method and the capacitively coupled plasma (CPP) CVD method.

[0123] To fabricate carbon nanostructures CNb, a first plasma treatment is first performed using the RI-PECVD method. In this first plasma treatment, microwaves having a frequency of 2.00 to 3.00 GHz are generated with a power of 300 to 500 W in a plasma generation chamber to which a radical source gas is supplied, generating a surface wave plasma containing radicals, which is then introduced into a reaction chamber. Furthermore, a source gas, such as a carbon-based gas, is supplied to the reaction chamber at a flow rate of 80 to 120 sccm, and a reaction contributing gas is supplied at a flow rate of 40 to 60 sccm. The pressure in the reaction chamber is controlled to, for example, about 0.5 to 1.5 Pa.

[0124] While the source gas is being supplied to the reaction chamber, a high-frequency voltage of 80 to 120 MHz is applied between the partition wall of the reaction chamber and the metal substrate 23B with a power of, for example, 300 to 500 W to generate capacitively coupled plasma CCP. As a result, an amorphous carbon layer AC is formed on the surface of the metal substrate 23B, and a base 43 grows on the amorphous carbon layer AC. The processing time for the first plasma treatment is, for example, about 5 to 15 minutes.

[0125] Next, a second plasma treatment is performed by the CPP-CVD method. In the second plasma treatment, the metal substrate 23B on which the base 43 is formed is heated to a temperature of 600 to 800°C by a heater in the reaction chamber. Then, a carbonaceous gas as a raw material gas is supplied to the reaction chamber at a flow rate of 80 to 120 sccm, and a reaction contributing gas is supplied at a flow rate of 40 to 60 sccm. The pressure in the reaction chamber is controlled to, for example, 5 to 15 Pa.

[0126] In this state, a high frequency voltage of, for example, 2000 to 3000 W and a frequency of 12 to 15 MHz is applied between the metal substrate 23B and the upper electrode placed above the metal substrate 23B. As a result, a plurality of extensions 44 are formed on the surface of each base 43 formed on the metal substrate 23B.

[0127] The electricity storage device 10B of the third embodiment can be charged and discharged by the electrode reactions of the chemical formulas (1) and (2) described in the first embodiment. When the electricity storage device 10A is charged, Li, which is involved in charging and discharging, is deposited on the carbon nanostructures CNb constituting the active material layer 25B of the first electrode 20, forming a layer of Li. Li is deposited in the gaps between the base portions 43 of the carbon nanostructures CNb and in the gaps between the extension portions 44, and also deposited above the carbon nanostructures CNb to form a layer.

[0128] 16 shows images I3a, I3b, I3c, and I3d illustrating an example of active material layer 25B according to the third embodiment. Images I3a and I3c were taken in the thickness direction, while images I3b and I3d were taken in a direction perpendicular to the thickness direction of metal substrate 23B. Metal substrate 23B in this example is a Cu foil.

[0129] The photographed images I3a and I3b shown on the left side of Fig. 16 show a first state in which the base 43 of the carbon nanostructure CNb has been formed. The photographed images I3c and I3d shown on the right side of Fig. 16 show a second state in which an extension has been formed on the surface of the base 43. Table 6 below shows the processing conditions for the first plasma treatment (RI-PECVD) for forming the base 43 and the processing conditions for the second plasma treatment (CCP-CVD) for forming the extension 44.

[0130] [Table 6]

[0131] A lithium-ion battery coin cell was fabricated using the active material layer 25B shown in images I3c and I3d under the conditions of Table 1 described in the first embodiment. In this lithium-ion battery, Li was deposited on the first electrode 20B during charging due to the electrode reaction of chemical formula (2) described in the first embodiment. Li was deposited in the gaps between the base portions 43 of the carbon nanostructures CNb and in the gaps between the extension portions 44, and also deposited above the carbon nanostructures CNb to form a layer.

[0132] The electricity storage device 10B of the third embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a temperature suitable for storage at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Therefore, even with the electricity storage device 10B of the third embodiment, self-discharge and performance degradation can be suppressed by storing the electricity storage device 10B in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the third embodiment can achieve various effects similar to those described in the first embodiment.

[0133] 4. Fourth embodiment: Fig. 17 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20C included in an electricity storage device 10C that is a storage target in the storage system and storage method of the fourth embodiment. Fig. 17 illustrates a cross-sectional structure of the first electrode 20C in an arbitrary cross section along the thickness direction.

[0134] The storage system and storage method of the fourth embodiment are the same as those described in the first embodiment (FIGS. 1 and 4), except that the configuration of the electricity storage device 10C to be stored is different. The electricity storage device 10C of the fourth embodiment has almost the same configuration as the electricity storage device 10 of the first embodiment, except that the configuration of the first electrode 20C is different.

[0135] The first electrode 20C of the electricity storage device 10C has a metal substrate 23C having a plurality of protrusions 46 on its plate surface. Each protrusion 46 is composed of fine metal particles MP. The protrusions 46 include those composed of a single metal particle MP and those composed of a plurality of metal particles MP densely packed together. The metal particles MP and the protrusions 46 are composed of the same metal as the metal substrate 23C. On the surface of the metal substrate 23C, regions where the protrusions 46 are densely packed and regions where the number of protrusions 46 is small are distributed throughout.

[0136] To obtain protrusions 46 of appropriate dimensions, the particle diameter of the metal particles MP when viewed in the thickness direction of the metal substrate 23C is preferably 5 nm or more and 55 nm or less. Furthermore, the average particle diameter of the metal particles MP is preferably 8 nm or more and 30 nm or less. In this specification, "particle diameter" refers to the maximum value of particle diameters in all directions measured in multiple images taken directly facing the metal substrate 23C using, for example, a scanning electron microscope or the like.

[0137] In order to realize an appropriate distribution density of the protrusions 46, the distribution density of the metal particles MP on the metal substrate 23C should be 1 particle / μm 2 More than 1000 pieces / μm 2 It is preferable that the distribution density of metal particles MP is equal to or less than 1000. The "distribution density of metal particles MP" here corresponds to the number of metal particles MP distributed per unit area of ​​the metal substrate 23C, which can be observed when viewed in the thickness direction of the metal substrate 23C.

[0138] The height of the protrusions 46 when viewed in a direction perpendicular to the thickness direction of the metal substrate 23C is preferably 5 nm or more and 300 nm or less. The height of the protrusions 46 is measured as the distance from the flat surface at the bottom of the protrusions 46 to the top of the protrusions 46 on an image taken from a direction perpendicular to the thickness direction of an arbitrary region of the metal substrate 23C using, for example, a scanning electron microscope.

[0139] On the surface of the metal substrate 23C, a plurality of carbon nanostructures CNc are arranged, each of which is mainly composed of graphene GF as explained in Fig. 3 and extends linearly on the surface of the metal substrate 23C. Here, the "main component" may be, for example, a component whose content ratio in the whole is 50 mass % or more. Furthermore, "linear" may also be referred to as fibrous, thread-like, or string-like, and it is preferable that the length is at least 7 to 8 times the diameter.

[0140] The carbon nanostructure CNc preferably has a carbon nanotube-like structure in which a graphene sheet is rolled into a cylindrical shape. Because the carbon nanostructure CNc is a graphite-like substance, it has higher electrical conductivity than carbon materials such as activated carbon.

[0141] The diameter of the carbon nanostructure CNc may be, for example, 1 nm or more and 15 nm or less, and the length of the carbon nanostructure CNc when stretched out straight may be, for example, 100 nm or more and 2000 nm or less.

[0142] Carbon nanostructures CNc constitute the active material layer 25C of the first electrode 20C. As shown in the photographed image I4 of the embodiment in FIG. 18, which will be referred to later, the carbon nanostructures CNc extend linearly on the surface of the metal substrate 23C when viewed in the thickness direction of the metal substrate 23C, and are distributed over the entire surface of the metal substrate 23C. The carbon nanostructures CNc are randomly distributed on the surface of the metal substrate 23C. The carbon nanostructures CNc can also be interpreted as extending in a manner that threads between the protrusions 46. The carbon nanostructures CNc may include those that extend through the region above the protrusions 46.

[0143] The manufacturing method of the protrusions 46 and the carbon nanostructures CNc is disclosed in the specification of Japanese Patent Application No. 2023-069934. The protrusions 46 can be formed by plasma treatment of the smooth surface of the metal substrate 23C by the RI-PECVD method. The carbon nanostructures CNc can be produced by plasma treatment of the metal substrate 23C on which the protrusions 46 have been formed by the CPP-CVD method.

[0144] The following describes the plasma treatment by the RI-PECVD method for forming the convex portions 46. In this plasma treatment, first, microwaves with a power of 300 to 500 W and a frequency of 2.00 to 3.00 GHz are introduced into the plasma generation chamber, and a radical source gas such as hydrogen is supplied to generate surface wave plasma containing radicals.

[0145] Next, the surface wave plasma generated in the plasma generation chamber is introduced into the reaction chamber where the base material of the metal substrate 23C is placed, and raw material gas is supplied. A high-frequency voltage with a power of, for example, 300 to 500 W and a frequency of 80 to 120 MHz is applied by a power supply unit. This generates a capacitively coupled plasma in the reaction chamber. During this plasma processing, the pressure in the reaction chamber is controlled to, for example, about 1.0 to 3.0 Pa.

[0146] When the capacitively coupled plasma containing radicals comes into contact with the base material of the metal substrate 23C, metal particles constituting the base material of the metal substrate 23C are scattered and adhere to the metal substrate 23C again. As a result, the convex portions 46 constituted by the above-mentioned metal particles MP are formed. The processing time for this plasma treatment is, for example, about 5 to 15 minutes.

[0147] The plasma processing of the CCP-CVD method for producing carbon nanostructures CNc will be described. First, the metal substrate 23C on which the protrusions 46 are formed is placed in a reaction chamber and heated by a heater to a temperature of, for example, 600 to 800°C. Then, a source gas containing a carbon-based gas such as methane (CH4) or hexafluoroethane (C2F6) and a reaction contributing gas such as H2 or Ar is supplied into the reaction chamber. The flow rate of the carbon-based gas may be, for example, 80 to 120 sccm, and the flow rate of the reaction contributing gas may be, for example, 40 to 60 sccm. The pressure in the reaction chamber is controlled to be 30 Pa or more and 50 Pa or less.

[0148] In this state, a high frequency voltage of, for example, 300 to 700 W power and 12 to 15 MHz frequency is applied between the metal substrate 23C and an upper electrode placed above the metal substrate 23C. As a result, carbon nanostructures CNc are generated starting from the protrusions 46 formed on the metal substrate 23C. The processing time for this plasma treatment is, for example, about 5 to 15 minutes.

[0149] The electricity storage device 10C of the fourth embodiment can be charged and discharged by the electrode reactions of chemical formulas (1) and (2) described in the first embodiment. When the electricity storage device 10C is charged, Li, which is involved in charging and discharging, is precipitated on the surface of the first electrode 20C to form a Li layer. This is because the carbon nanostructure CNc functions as an active material, promoting the precipitation of lithium on the surface layer of the first electrode 20C. In addition, the precipitation of Li on the surface of the first electrode 20C is promoted from the protrusions 46 of the metal substrate 23C. This is based on findings derived by the inventor of the present invention from experimental results based on nucleation theory.

[0150] FIG. 18 shows a captured image I4 illustrating an example of the first electrode 20C of the fourth embodiment. The captured image I4 was taken in the thickness direction of the metal substrate 23C. The metal substrate 23C in the captured image I4 is a Cu foil. As shown in the captured image I4, convex portions 46 composed of metal particles MP are formed on the surface of the metal substrate 23C, and linear carbon nanostructures CNc are distributed over the entire surface of the metal substrate 23C. The processing conditions for the plasma processing to form the convex portions 46 and the carbon nanostructures CNc on the metal substrate 23C in the captured image I4 are shown in Table 7 below.

[0151] [Table 7]

[0152] A lithium-ion battery coin cell was fabricated using the first electrode 20C shown in photographed image I4 under the conditions of Table 1 described in the first embodiment. During charging of this lithium-ion battery, a layer of Li was formed on the surface of the first electrode 20C due to the electrode reaction of chemical formula (2) described in the first embodiment.

[0153] The electricity storage device 10C of the fourth embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a temperature suitable for storage at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Even with the electricity storage device 10C of the fourth embodiment, self-discharge and performance degradation can be suppressed by storing it in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the fourth embodiment can achieve various effects similar to those described in the first embodiment.

[0154] 5. Fifth embodiment: Fig. 19 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20D included in an electricity storage device 10D that is a storage target in the storage system and storage method of Embodiment 5. Fig. 19 illustrates a cross-sectional structure of the first electrode 20D in an arbitrary cross section along the thickness direction.

[0155] The storage system and storage method of the fifth embodiment are the same as those described in the first embodiment (FIGS. 1 and 4), except that the configuration of the electricity storage device 10D to be stored is different. The electricity storage device 10D of the fifth embodiment has almost the same configuration as the electricity storage device 10 of the first embodiment, except that it includes a first electrode 20D with a different configuration.

[0156] The first electrode 20D has a configuration in which an active material layer 25D is formed on the surface of a metal substrate 23D. A fine uneven structure CS on the order of microns is formed on the surface of the metal substrate 23D. The active material layer 25D is formed as a thin film so as to densely cover the surface of the uneven structure CS. The average thickness of the active material layer 25D may be, for example, 0.1 μm to 15.0 μm.

[0157] The active material layer 25D has a surface uneven structure CSs with smaller unevenness dimensions than the uneven structure CS of the metal substrate 23D. To improve the battery performance of the power storage device 10D, it is preferable that a plurality of granular surface protrusions 48, each having a width of 0.1 μm or more and 10.0 μm or less, be densely distributed on the surface of the active material layer 25D when viewed in the thickness direction of the metal substrate 23D. The "width of the surface protrusions 48" refers to the maximum value of the widths of a single surface protrusion 48 measured in all directions perpendicular to the thickness direction of the metal substrate 23D. Note that minute voids VD may be formed inside the uneven structure CS of the metal substrate 23D and the active material layer 25D during their formation.

[0158] The active material layer 25D is mainly composed of a carbon nanostructure CNd composed of nanographene and amorphous carbon. The active material layer 25D has a configuration in which nanographene and amorphous carbon particles are deposited. The nanographene and amorphous carbon particles include those having a spherical shape and those having a plate-like shape. The surface protrusions 48 of the active material layer 25D described above include those composed of a single particle and those composed of a random collection of multiple particles. Note that hydroxyl groups may remain inside the active material layer 25D as impurities introduced during the manufacturing process.

[0159] A manufacturing method of the first electrode 20D is disclosed in the specification of Japanese Patent Application No. 2023-128891. The concavo-convex structure CS and the active material layer 25D of the metal substrate 23D in the first electrode 20D are formed by plasma treatment. The first electrode 20D is formed by immersing the metal substrate 23D in a solution containing alcohol stored in a reaction chamber, generating plasma using a plasma electrode installed above the liquid surface of the solution while supplying a reactive gas to the reaction chamber, and irradiating the plasma onto the metal substrate 23D in the solution.

[0160] The alcohols contained in the solution are, for example, ethanol (CH 6O) or other primary alcohols. For example, Ar or H2 can be used as the reactive gas. In the plasma treatment, the reactive gas is supplied to the reaction chamber at a flow rate of, for example, about 1 to 10 slm. The unit "slm" indicates the flow rate per minute at 1 atmosphere (atm) and 0°C. The pressure inside the reaction chamber is, for example, 0.5 x 10 5 ~1.5×10 5 The pressure is controlled to about Pa.

[0161] The plasma electrode is made of a carbon substrate such as sintered graphite. The distance between the tip of the plasma electrode and the liquid surface of the solution may be, for example, about 1 to 10 mm. The high-frequency voltage for generating plasma may be, for example, 5 to 15 kV, and the frequency may be, for example, 50 to 80 Hz.

[0162] When plasma irradiation of the metal substrate 23D in the solution begins, the alcohols and hydrocarbons in the solution are decomposed, generating hydrogen atoms and radicals in the solution. These hydrogen atoms and radicals erode the surface of the metal substrate 23D, forming a fine uneven structure CS. While the plasma is being irradiated, the hydrogen atoms and radicals continue to erode the surface of the metal substrate 23D, causing the depressions and protrusions of the uneven structure CS to grow larger. During this time, hydrogen atoms enter the interior of the metal substrate 23D, forming minute cavities VD within the uneven structure CS.

[0163] During the formation of the concave-convex structure CS, carbon atoms generated in the solution by decomposition of alcohol due to plasma irradiation precipitate as nanographene and amorphous carbon particles, which begin to adhere to the surface of the concave-convex structure CS of the metal substrate 23D. In parallel with the growth of the concave-convex structure CS on the surface of the metal substrate 23D, nanographene and amorphous carbon particles are deposited to cover the surface of the concave-convex structure CS, thereby forming an active material layer 25D that covers the surface of the concave-convex structure CS. During this growth process, tiny voids VD may also be formed inside the active material layer 25D.

[0164] The electricity storage device 10D of the fifth embodiment has the first electrode 20D described above, and is therefore capable of charging and discharging through the electrode reactions of the chemical formulas (1) and (2) described in the first embodiment. When the electricity storage device 10D is charged, Li, which is involved in charging and discharging, is deposited on the first electrode 20D to form a Li layer.

[0165] 20(a) shows a photographed image I5 of active material layer 25D of first electrode 20D as an example, photographed in the thickness direction of metal substrate 23D. Metal substrate 23D in photographed image I5 is a Cu foil. The processing conditions for the plasma treatment for forming first electrode 20D are shown in Table 8 below. In active material layer 25D in photographed image I5, a plurality of granular surface protrusions 48 having a width of 0.1 μm or more and 10.0 μm or less were densely distributed.

[0166] [Table 8]

[0167] FIG. 20(b) shows the Raman spectrum of the active material layer 25D of the photographed image I5. In this graph, the D band (1340 cm -1 ) and G band (1580 cm -1 ) was observed. This result indicates that active material layer 25D is formed mainly from a carbon nanostructure made of nanographene and amorphous carbon.

[0168] A lithium-ion battery coin cell was fabricated using first electrode 20D shown in photographed image I5 under the conditions of Table 1 described in the first embodiment. During charging of this lithium-ion battery, a layer of Li was formed on the surface of first electrode 20D due to the electrode reaction of chemical formula (2) described in the first embodiment.

[0169] The electricity storage device 10D of the fifth embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a temperature suitable for storage at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Therefore, even with the electricity storage device 10D of the fifth embodiment, self-discharge and performance degradation can be suppressed by storing the electricity storage device 10D of the fifth embodiment in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the fifth embodiment can achieve various effects similar to those described in the first embodiment.

[0170] 6. Sixth embodiment: 21 is a schematic diagram illustrating an example of an electricity storage device 10E that is the storage target of the storage system and storage method of the sixth embodiment. The storage system and storage method of the second embodiment are the same as those described in the first embodiment (FIGS. 1 and 4), except that the configuration of the electricity storage device 10E that is the storage target is different. The electricity storage device 10E of the sixth embodiment has almost the same configuration as the electricity storage device 10 of the first embodiment, except that the configuration of the first electrode 20E is different.

[0171] A first electrode 20E of an electricity storage device 10E of the sixth embodiment is composed of a metal substrate 23E that functions as a current collector. No active material layer is provided on the metal substrate 23E. As shown in the balloon in FIG. 21 , the metal substrate 23E has a plurality of protrusions 46a formed of fine metal particles MP on its plate surface. When the electricity storage device 10E is charged, Li is deposited on the surfaces of the protrusions 46a.

[0172] In order to smoothly deposit Li during charging, the area of ​​the projection region obtained by projecting the protrusions 46a onto the surface of the metal substrate 23E is 10 nm 2 More than 10000nm 2 The density of the protrusions 46a on the surface of the metal substrate 23E is preferably 1 / μm 2 More than 1000 pieces / μm 2Alternatively, it is preferable that the average value of the maximum length of the projected area of ​​the protrusions 46a projected onto the surface of the metal substrate 23E is 10 nm or more and 200 nm or less, and the area occupied by the projected area is 1 / 10 or more of the area of ​​the surface of the metal substrate 23E.

[0173] The method for forming the protrusions 46a of the metal substrate 23E is also substantially the same as the protrusions 46 described in the fourth embodiment. The protrusions 46a of the metal substrate 23E can be formed by a CVD method on the metal substrate 23E. The method for forming the protrusions 46a of the metal substrate 23E is the same as the method for forming the "protrusions PR1" disclosed in JP 2022-187895 A.

[0174] The electricity storage device 10E of the sixth embodiment can be charged and discharged by the electrode reactions of the chemical formulas (1) and (2) described in the first embodiment. When the electricity storage device 10E is charged, Li, which is involved in charging and discharging, is deposited from the protrusions 46a of the metal substrate 23E as starting points, and a layer of Li is formed on the surface of the first electrode 20E.

[0175] 22 shows a captured image I6 illustrating an example of the first electrode 20E of the sixth embodiment. The captured image I6 was taken in the thickness direction of the metal substrate 23E. The metal substrate 23E in the captured image I6 is a Cu foil, and the metal particles MP are Cu particles. As shown in the captured image I6, convex portions 46a formed by the metal particles MP are distributed over the entire surface of the metal substrate 23E.

[0176] A lithium-ion battery coin cell was fabricated using first electrode 20E shown in photographed image I6 under the conditions of Table 1 described in the first embodiment. During charging of the lithium-ion battery, a layer of Li was formed on the surface of first electrode 20E due to the electrode reaction of chemical formula (2) described in the first embodiment.

[0177] The electricity storage device 10E of the sixth embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a temperature suitable for storage at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Therefore, even with the electricity storage device 10E of the sixth embodiment, self-discharge and performance degradation can be suppressed by storing the electricity storage device 10E in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the sixth embodiment can achieve various effects similar to those described in the first embodiment.

[0178] 7. Seventh embodiment: 23(a) and 23(b) are schematic cross-sectional views illustrating the cross-sectional structure of a first electrode 20F included in an electricity storage device 10F that is the target of storage in the storage system and storage method of the seventh embodiment, respectively. Each of FIGS. 23(a) and 23(b) illustrates the cross-sectional structure of the first electrode 20F at an arbitrary cut surface along the thickness direction.

[0179] The storage system and storage method of the seventh embodiment are the same as those described in the first embodiment (FIGS. 1 and 4), except that the configuration of the electricity storage device 10F to be stored is different. The electricity storage device 10F of the seventh embodiment has almost the same configuration as the electricity storage device 10E of the sixth embodiment, except that the surface structure of the metal substrate 23F of the first electrode 20F is different.

[0180] In this embodiment, a fine uneven structure is formed on the outer surface of the metal substrate 23F. The uneven structure includes a plurality of convex structure portions 52 each having a maximum width Wmax of 0.5 μm or more and 30.0 μm or less. The convex structure portions 52 are portions that protrude in the thickness direction of the metal substrate 23F. As will be described later, the convex structure portions 52 are composed of one or more metal particles MP. The metal particles MP are composed of the same type of metal as the metal that constitutes the metal substrate 23F. When the metal substrate 23F is composed of an alloy, the metal particles MP are composed of the same type of metal as the main metal of the alloy.

[0181] The maximum width Wmax of the convex structure portion 52 corresponds to the maximum width of the convex structure portion 52 in all directions, as measured in an image of the metal substrate 23F photographed in the thickness direction using, for example, a scanning electron microscope. "All directions" refers to all directions perpendicular to the thickness direction of the metal substrate 23F.

[0182] The lower limit of the maximum width Wmax of the convex structure 52 is preferably 0.6 μm or more, and more preferably 0.8 μm or more. The upper limit of the maximum width Wmax of the convex structure 52 is preferably 28.0 μm or less, and more preferably 25.0 μm or less. Note that, in addition to the convex structure 52 within the above-mentioned range of the maximum width Wmax, the surface of the metal substrate 23F may also include convex portions having a width smaller than the lower limit of the above-mentioned range of the maximum width Wmax.

[0183] Figures 23(a) and 23(b) each show examples of the convex structure 52 having a different shape. Figure 23(a) shows a first convex body 52a as a first example of the convex structure 52. Figure 23(b) shows a second convex body 52b as a second example of the convex structure 52, and a third convex body 52c as a third example of the convex structure 52. The example forms of the convex structure 52 will be explained below in order.

[0184] 23(a). The first convex body 52a, which is a first embodiment of the convex structure 52, is composed of a plurality of minute metal particles MP having a particle diameter Pp of 0.5 μm or more and 5.0 μm or less, densely stacked together. In this specification, the term "particle diameter" refers to the maximum value of the particle diameters in all directions measured in a plurality of images taken directly facing the metal substrate 23F using, for example, a scanning electron microscope or the like.

[0185] The first convex body 52a has a structure in which multiple tiny metal particles MP are gathered in a tuft-like shape, and an uneven structure in which the tiny metal particles MP are densely arranged is formed on the surface, and the overall structure is one in which it protrudes from the surrounding area.

[0186] In the first convex bodies 52a, the maximum width Wmax of the convex structure 52 corresponds to the maximum distance between the ends of the plurality of metal particles MP constituting the first convex bodies 52a in the direction perpendicular to the thickness direction of the metal substrate 23F. The lower limit of the particle diameter Pp of each metal particle MP constituting the first convex bodies 52a is preferably 0.6 μm or more, and more preferably 0.8 μm or more. The upper limit of the particle diameter Pp of the metal particles MP is preferably 4.0 μm or less, and more preferably 3.0 μm or less.

[0187] The first convex body 52a has a height Hp of 1.0 μm or more and 15.0 μm or less. The height Hp of the first convex body 52a corresponds to the distance in the thickness direction of the metal substrate 23F between the bottom and top ends of the first convex body 52a, as measured, for example, in an image captured by a scanning electron microscope from a direction perpendicular to the thickness direction of the metal substrate 23F. The lower limit of the height Hp of the first convex body 52a is preferably 2.0 μm or more, and more preferably 4.0 μm or more. The upper limit of the height Hp of the first convex body 52a may be 12.0 μm or less, or may be 10.0 μm or less.

[0188] 23(b) . The second convex body 52b, which is a second embodiment of the convex structure 52, and the third convex body 52c, which is a third embodiment, have in common the fact that they are composed of metal particles MP recognized as individual particles, but they differ in size and shape. The second convex body 52b and the third convex body 52c differ, in particular, in their heights. The heights of the convex bodies 52b and 52c correspond to the distance in the thickness direction of the metal substrate 23F between the bottom and top ends of the convex bodies 52b and 52c, as measured, for example, in an image captured by a scanning electron microscope from a direction perpendicular to the thickness direction of the metal substrate 23F.

[0189] The particle diameter Pq of the second convex bodies 52b is 0.5 μm or more and 5.0 μm or less, and its height Hq is approximately equal to or less than the particle diameter Pq. In the second convex bodies 52b, the particle diameter Pq corresponds to the maximum width Wmax of the convex structure portion 52. The lower limit of the particle diameter Pq of the second convex bodies 52b is preferably 0.6 μm or more, and more preferably 0.8 μm or more. The upper limit of the particle diameter Pq of the second convex bodies 52b may be 4.5 μm or less, or may be 4.0 μm or less.

[0190] The third convex bodies 52c have a vertically elongated shape. The third convex bodies 52c have a particle diameter Pr of 0.5 μm or more and 8.0 μm or less, and have a height Hr greater than the particle diameter Pr. The particle diameter Pr of the third convex bodies 52c corresponds to the maximum width Wmax of the convex structure portion 52. The lower limit of the particle diameter of the third convex bodies 52c is preferably 0.6 μm or more, and more preferably 0.8 μm or more. The upper limit of the particle diameter of the third convex bodies 52c may be 7.0 μm or less, or may be 5.0 μm or less.

[0191] The height Hr of the third convex body 52c may be, for example, 1.0 μm or more and 12.0 μm or less. The lower limit of the height Hr of the third convex body 52c may be 2.0 μm or more, or 3.0 μm or more. The upper limit of the height Hr of the third convex body 52c may be 10.0 μm or less, or 8.0 μm or less.

[0192] The uneven structure on the surface of the metal substrate 23F may have, for example, a configuration in which the first convex bodies 52a are densely arranged on the surface of the metal substrate 23F. The uneven structure on the surface of the metal substrate 23F may have a configuration in which the second convex bodies 52b and the third convex bodies 52c are arranged between the first convex bodies 52a. The uneven structure on the surface of the metal substrate 23F may have a configuration in which the second convex bodies 52b or the third convex bodies 52c are distributed over the entire surface of the metal substrate 23F. The uneven structure on the surface of the metal substrate 23F may have a configuration in which the first convex bodies 52a and the third convex bodies 52c are arranged between the second convex bodies 52b arranged over the entire surface of the metal substrate 23F. The uneven structure on the surface of the metal substrate 23F may have a configuration in which the first convex bodies 52a, the second convex bodies 52b, and the third convex bodies 52c are mixed. The uneven structure on the surface of the metal substrate 23F may be configured to include, in addition to the convex structure portion 52, particle-like convex portions that are smaller than the second convex bodies 52b and the third convex bodies 52c.

[0193] The area of ​​the projected region obtained by projecting the convex structure 52 including the convex bodies 52a, 52b, and 52c in the thickness direction of the metal substrate 23F is 0.01 μm 2 Larger than 10000μm 2 Furthermore, the density of the projected area of ​​the convex structure 52 when the metal substrate 23F is projected in the thickness direction is 1 piece / mm 2 More than 108 pieces / mm 2 The convex structure 52 having such dimensions can be easily formed by surface treatment using electrolytic deposition on the base material of the metal substrate 23F.

[0194] A method for forming the convex structure 52 is disclosed in Japanese Patent Application Laid-Open Publication No. 2024-016511. When the metal substrate 23F is made of Cu, an uneven structure including the convex structure 52 can be formed on the surface of the metal substrate 23F by performing electrolytic deposition under the following conditions. In the electrolytic deposition, sulfuric acid (H2SO4) having a concentration of, for example, about 0.5 to 2.0 M (volume molar concentration mol / L) is used as the electrolyte. A voltage of about 0.5 to 2.0 V is applied to an electrode plate made of crude copper as the anode, and the base material of the metal substrate 23F as the cathode, and a current of about 80.0 to 200.0 mA is passed through the electrode plate. As a result, Cu on the electrode plate is oxidized and dissolved into the electrolyte as Cu ions. The Cu ions migrate toward the base material of the metal substrate 23F, where they are reduced and precipitated on the surface of the base material of the metal substrate 23F. The precipitated Cu particles form the convex structure 52 one after another on the base material surface.

[0195] The electricity storage device 10F of the seventh embodiment can be charged and discharged by the electrode reactions of the chemical formulas (1) and (2) described in the first embodiment. When the electricity storage device 10F is charged, Li, which is involved in charging and discharging, is deposited from the convex structure portion 52 of the metal substrate 23F as an origin, and a layer of Li is formed on the surface of the first electrode 20F.

[0196] 24 shows photographed images I7a, I7b, I7c, and I7d illustrating examples of the convex structure portion 52 of the first electrode 20F of the seventh embodiment. The photographed direction of the photographed images I7a and I7c is a direction perpendicular to the thickness direction of the metal substrate 23F. The photographed direction of the photographed images I7b and I7d is the thickness direction of the metal substrate 23F.

[0197] The photographed images I7a and I7b in the upper column of Fig. 24 show an example of a first convex body 52a, which is a first embodiment of the convex structure portion 52. The first convex body 52a is composed of a plurality of minute metal particles MP densely stacked on top of each other. The photographed images I7c and I7d in the lower column of Fig. 24 show a second convex body 52b, which is a second embodiment of the convex structure portion 52, and a third convex body 52c, which is a third embodiment. The second convex body 52b and the third convex body 52c are composed of metal particles MP that are recognized as individual bodies.

[0198] The first convex body 52a, the second convex body 52b, and the third convex body 52c in the photographed images I7a, I7b, I7c, and I7d were fabricated by performing a surface treatment by electrolytic deposition on Cu foil as the metal substrate 23F. The electrolytic deposition for forming the second convex body 52b and the third convex body 52c used a 1.5 M H2SO4 solution as the electrolyte, and a DC voltage of 1.0 V was applied to the Cu foil in the electrolyte, resulting in a current of 128 mA. The distance between the substrate and the electrode was 3.5 cm.

[0199] A lithium-ion battery coin cell was fabricated using first electrode 20F shown in photographed images I7a, I7b, I7c, and I7d under the conditions of Table 1 described in the first embodiment. During charging of the lithium-ion battery, a layer of Li was formed on the surface of first electrode 20F due to the electrode reaction of chemical formula (2) described in the first embodiment.

[0200] The electricity storage device 10F of the seventh embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a temperature suitable for storage at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Therefore, even with the electricity storage device 10F of the seventh embodiment, self-discharge and performance degradation can be suppressed by storing the electricity storage device 10F of the seventh embodiment in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the seventh embodiment can achieve various effects similar to those described in the first embodiment.

[0201] 8. Eighth embodiment: The storage system and storage method of the eighth embodiment will be described with reference to FIGS. 25, 26, and 27, with reference to a metal substrate 23G of a first electrode 20G included in an electricity storage device 10G that is the storage target.

[0202] 25 is a schematic diagram showing the configuration of an electricity storage device 10G according to an eighth embodiment. The electricity storage device 10G has almost the same configuration as the electricity storage device 10E according to the sixth embodiment, except that it has a metal substrate 23G having smooth surfaces and having been subjected to a heat treatment described below.

[0203] Through extensive research, the inventors of the present invention have found that if a metal substrate heat-treated under atmospheric gas is used as an electrode for an electricity storage device, high charge / discharge performance can be achieved by the electrode reactions of chemical formulas (1) and (2) described in the first embodiment, even without providing an active material layer or a textured structure. Details of this are disclosed in the specification of Japanese Patent Application No. 2024-023186.

[0204] The heat treatment of the metal substrate 23G is performed by heating it in an atmospheric gas at a predetermined temperature for a predetermined time. In this embodiment, a reducing gas is used as the atmospheric gas. For example, H2 can be used as the reducing gas. Instead of H2, for example, carbon monoxide (CO), ammonia (NH3), hydrocarbon gas, etc. can be used as the reducing gas. For example, methane (CH4), ethane (C2H5), propane (C3H8), butane (C4H 10 ), ethylene (C2H4), acetylene (C2H2), etc. may also be used.

[0205] The reducing gas is not limited to the above-mentioned examples, but may be any gas that can cause a reduction reaction of the base material of the metal substrate 23G during heat treatment, and may be a hydrogen compound containing at least H, N, or C, an oxygen compound, or a compound having dangling bonds of these.

[0206] Instead of the reducing gas, an inert gas such as argon (Ar), helium (He), xenon (Xe), or nitrogen (N) may be used as the atmospheric gas.

[0207] In the heat treatment, the atmospheric gas is preferably adjusted to a predetermined oxygen partial pressure at the treatment temperature of the heat treatment so as not to oxidize the metal substrate 23G. The oxygen partial pressure of this atmospheric gas may be set to a value equal to or less than the thermal equilibrium oxygen partial pressure derived from a graph showing the relationship between the standard free energy of oxide formation and temperature, which is obtained by thermodynamic calculation. For example, when the inert gas is Ar or N2, the oxygen partial pressure in the atmospheric gas is set to 10 -6 If the oxygen partial pressure in the atmospheric gas is higher than the thermal equilibrium oxygen partial pressure, the oxygen partial pressure may be reduced by purifying the atmospheric gas using a purification device.

[0208] The heat treatment temperature in this embodiment may be, for example, 400° C. or higher and 1000° C. or lower. The heat treatment temperature is preferably 500° C. or higher, and more preferably 600° C. or higher. The heat treatment temperature is further preferably 700° C. or higher, and more preferably 800° C. or higher.

[0209] The treatment time of the heat treatment may be determined appropriately depending on the type of metal constituting the metal substrate, the treatment temperature in the heat treatment, etc. The treatment time of the heat treatment may be determined as the time required for the metal structure of the metal substrate to undergo a predetermined change or the time required for most of the metal oxide in the metal substrate to be reduced.

[0210] The heat treatment time may be set to be longer than the reduction time of the metal oxide, but from the viewpoint of suppressing increases in manufacturing costs due to longer process times, the heat treatment time is preferably, for example, 5 minutes or more and 60 minutes or less. The heat treatment time is preferably 7 minutes or more and 30 minutes or less. The heat treatment time is more preferably 8 minutes or more and 20 minutes or less.

[0211] As will be described below, a two-dimensional diffraction image of the Debye rings of the metal substrate 23G that has been subjected to the above heat treatment is obtained by a two-dimensional X-ray detector as a discontinuous arc-shaped image in which points or line segments are arranged.

[0212] 26 and 27 show the change in X-ray diffraction (XRD) of the metal substrate 23G when subjected to the heat treatment. FIG. 26 shows the X-ray diffraction patterns of a Cu foil as an example of the metal substrate 23G before and after the heat treatment. In FIG. 26, the numbers in parentheses after Cu indicate Miller indices. FIG. 27 shows two-dimensional diffraction images of the Debye rings of the same Cu foil obtained by a two-dimensional X-ray detector before and after the heat treatment. The specific conditions for the heat treatment performed on the Cu foil as an example of the metal substrate 23G that was the subject of the X-ray diffraction in FIGS. 26 and 27 are shown in Table 9 below.

[0213] [Table 9]

[0214] The X-ray diffraction pattern shown in Figure 26 shows that the number of prominent peaks decreased after the heat treatment under the conditions in Table 5. For example, the Cu(220) peak was reduced to an almost negligible level after the heat treatment. As a result, the ratio of the Cu(200) peak to the Cu(220) peak, I200 / I220, increased from 1 before the heat treatment to 2000 after the heat treatment. Furthermore, the Cu(200) peak and the Cu(400) peak became significantly smaller after the heat treatment. This change in the X-ray diffraction pattern indicates that the metal particles constituting the metal substrate became coarser due to the heat treatment.

[0215] In the two-dimensional diffraction image before heat treatment shown in Figure 27, the Debye rings corresponding to the peaks shown in Figure 26 were confirmed as clear, continuous solid line images. In contrast, in the two-dimensional diffraction image after heat treatment, the two-dimensional diffraction image of the Debye rings was obtained as a discontinuous arc-shaped image composed of arc-shaped points or line segments. This change in the two-dimensional diffraction image indicates that the heat treatment recrystallized the metal crystal structure in the metal substrate into a preferred orientation crystal structure. The blurred two-dimensional diffraction image shown in Figure 27 can be said to indicate the history of the metal substrate after heat treatment.

[0216] A lithium-ion battery coin cell was fabricated using the heat-treated Cu foil metal substrate 23G as the first electrode under the conditions of Table 1 described in the first embodiment. During charging, the lithium-ion battery formed a Li layer on the surface of the first electrode due to the electrode reaction of chemical formula (2) described in the first embodiment.

[0217] The electricity storage device 10G of the eighth embodiment shares a charge / discharge mechanism with the electricity storage device 10 of the first embodiment, and also shares a suitable storage temperature at which self-discharge is suppressed with the electricity storage device 10 of the first embodiment. Therefore, even for an electricity storage device 10G including a heat-treated metal substrate 23G of the eighth embodiment, self-discharge and performance degradation can be suppressed by storing the electricity storage device 10 of the first embodiment in a storage system at a storage temperature similar to that of the electricity storage device 10 of the first embodiment. In addition, the storage system and storage method of the eighth embodiment can achieve various effects similar to those described in the first embodiment.

[0218] 9. Other embodiments: The present invention is not limited to the configurations of the above-described embodiments and examples, and can also be realized in the following forms, for example. Any configurations described below as other embodiments are positioned as examples of forms for implementing the present invention, similar to the above-described embodiments and configurations and examples described as other embodiments within the above-described embodiments.

[0219] The storage system and storage method for an electricity storage device described in each of the above embodiments may be applied to a mobile body such as an automobile. In this case, for an electricity storage device in a mobile body that has been stopped for a long period of time, the temperature of the electricity storage device may be controlled to be maintained at the above-mentioned storage temperature by air-cooling means using a fan or refrigerant provided in the mobile body. Furthermore, the temperature control based on the above-mentioned storage temperature may be applied to an electricity storage device that supplies power to a moving mobile body or is being charged by a moving mobile body.

[0220] In each of the above embodiments, the storage temperature may be set according to the season or the outside air temperature. For example, when the outside air temperature is 30 to 45°C, such as in summer, the storage temperature of the power storage device 10 may be set to, for example, 35 to 50°C, and when the outside air temperature is 20°C or lower, such as in winter, the storage temperature of the power storage device 10 may be set to, for example, 25 to 35°C. In the storage system 100, the control unit 105 may automatically set the storage temperature as described above based on the detection result of the outside air temperature sensor. In this way, the amount of energy consumed to maintain the storage temperature can be significantly reduced, which is efficient.

[0221] In each of the above embodiments, the power storage device may be configured as a secondary battery other than a lithium ion battery or as another power storage device. The power storage device may be configured as, for example, an electric double layer capacitor. The power storage device may also be configured to use metal ions other than Li ions in charging and discharging. The power storage device may also be configured to use metal ions such as sodium (Na) ions, potassium (K) ions, magnesium (Mg) ions, etc. in charging and discharging. In the power storage device, the metal substrate of the first electrode may be made of a metal other than Cu. The metal substrate may be made of, for example, a Cu alloy, Al, an Al alloy, or another metal.

[0222] In the above-mentioned first, second, third, fourth, fifth, sixth, and seventh embodiments, the energy storage devices 10, 10A, 10B, 10C, 10D, 10E, and 10F have at least one of a first configuration having an active material layer of carbon nanostructures mainly composed of graphene on the plate surface of a metal substrate, and a second configuration having an uneven structure on the plate surface of a metal substrate, and therefore can be interpreted as being configured so that a layer of metal atoms formed by the deposition of metal atoms is formed on the surface of the electrode during charging.

[0223] 10. Example of morphology: The present invention can be realized in the following forms.

[0224] [First Aspect] The first aspect is provided as a method for storing an electricity storage device. The storage method of the first aspect includes the steps of charging an electricity storage device including a container filled with an electrolyte, metal atoms that ionize in the electrolyte and participate in charging and discharging, and electrodes disposed in the electrolyte, wherein the electricity storage device is configured such that, during charging, a layer of the metal atoms precipitates on the surface of the electrodes, and placing the charged electricity storage device in an open-circuit state and maintaining the temperature of the electricity storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower. According to findings obtained through original research by the inventors of the present invention, in an electricity storage device to which the storage method of the first embodiment is applied, the higher the environmental temperature is, at 25°C or higher, in an unloaded state, the more effectively self-discharge is suppressed. Furthermore, if the environmental temperature exceeds 65°C, problems such as deterioration of the electrolyte may occur. According to the storage method of the first embodiment, the electricity storage device is stored in an unloaded state at an environmental temperature of 25°C or higher and 65°C or lower, and therefore self-discharge and deterioration of the electricity storage device can be suppressed.

[0225] [Second embodiment] In the storage method of the first embodiment, the storage temperature may be 35°C or higher and 50°C or lower. According to the storage method of the second embodiment, self-discharge and deterioration of the electricity storage device can be suppressed even more effectively.

[0226] [Third embodiment] In the storage method described in the first embodiment or the second embodiment, the metal atoms may be lithium atoms, the electrode may have a metal substrate that functions as a current collector, and the electricity storage device may have an active material layer of a carbon nanostructure composed mainly of graphene on the plate surface of the metal substrate. According to the storage method of the third embodiment, it is possible to effectively suppress self-discharge and deterioration of an electricity storage device including a lithium ion battery.

[0227] [Fourth Mode] In the storage method according to the third mode, the carbon nanostructures may be carbon nanowalls extending from the smooth surface of the metal substrate. According to the storage method of the fourth embodiment, it is possible to effectively suppress self-discharge and deterioration of an electricity storage device that uses carbon nanowalls as an active material.

[0228] [Fifth Form] In the storage method of the third form, the surface of the active material layer may have a fine uneven structure in which a plurality of minute particles are densely arranged, and the carbon nanostructures may be arranged over the entire surface of the particles, extending in elongated shapes outward from the particles. According to the fifth storage method, it is possible to effectively suppress self-discharge and deterioration of an energy storage device having an active material layer in which a fine uneven structure is formed by granular material having carbon nanostructures formed over the entire surface.

[0229] [Sixth Mode] In the storage method of the third mode, the carbon nanostructure may have a base portion in which the graphene is laminated and extends elongatedly in the thickness direction of the metal substrate, and a plurality of extension portions made of carbon and extending from the base portion. According to the storage method of the sixth embodiment, it is possible to effectively suppress self-discharge and deterioration of an electricity storage device to which an active material layer including a carbon nanostructure having a base portion and an extension portion is applied.

[0230] [Seventh Form] In the storage method of the third form, the metal substrate may have a plurality of convex portions on the plate surface, and when the metal substrate is viewed in the thickness direction, a plurality of the carbon nanostructures extending linearly on the plate surface of the metal substrate may be distributed on the surface of the metal substrate. According to the seventh storage method, it is possible to effectively suppress self-discharge and deterioration of an electricity storage device having an electrode having a convex portion and a plurality of linearly extending carbon nanostructures on the surface of a metal substrate.

[0231] [Eighth embodiment] In the storage method of the third embodiment, a fine uneven structure may be formed on the surface of the metal substrate, and an active material layer mainly composed of the carbon nanostructure made of the nanographene and amorphous carbon may be formed so as to densely cover the surface of the uneven structure. According to the eighth storage method, it is possible to effectively suppress self-discharge and deterioration of an electricity storage device having an active material layer mainly composed of a carbon nanostructure composed of nanographene and amorphous carbon, which covers the uneven structure on the surface of a metal substrate.

[0232] [Ninth embodiment] In the storage method according to the first or second embodiment, the metal atoms are lithium atoms, the electrode has a metal substrate that functions as a current collector, the metal substrate has a plurality of protrusions on its plate surface where the lithium atoms are precipitated, and the area of ​​a projected region of the protrusions projected onto the plate surface of the metal substrate is 10 nm 2 More than 10000nm 2 and the density of the protrusions on the plate surface is 1 piece / μm 2 More than 1000 pieces / μm 2 The following is fine. According to the storage method of the ninth embodiment, it is possible to effectively suppress self-discharge and deterioration of an electricity storage device that includes, as a current collector, a metal substrate having a plurality of protrusions on its plate surface.

[0233] [Tenth Mode] In the storage method according to any one of the first, second, and ninth modes, the metal atoms are lithium atoms, the electrode has a metal substrate that functions as a current collector, the metal substrate has a plurality of protrusions on its plate surface where the lithium atoms are precipitated, the average maximum length of the projected area of ​​the protrusions projected onto the plate surface may be 10 nm or more and 200 nm or less, and the area occupied by the projected area may be 1 / 10 or more of the area of ​​the plate surface. According to the storage method of the tenth embodiment, it is possible to more effectively suppress self-discharge and deterioration of an electricity storage device that includes, as a current collector, a metal substrate having a plurality of protrusions on its plate surface.

[0234] [Eleventh embodiment] In the storage method described in the first or second embodiment, the metal atoms are lithium atoms, the electrode has a metal substrate that functions as a current collector, and the metal substrate may have a fine uneven structure on its plate surface that is made up of metal particles, has a maximum width of 0.5 μm or more and 30.0 μm or less, and is made up of a plurality of protrusions on whose surface the lithium atoms precipitate during charging. According to the storage method of the eleventh embodiment, it is possible to more effectively suppress self-discharge and deterioration of an electricity storage device that includes, as a current collector, a metal substrate having a plurality of convex bodies on its plate surface.

[0235] [Twelfth Mode] In the storage method described in the first or second mode, the metal atoms are lithium atoms, the electrode has a metal substrate that functions as a current collector, and the metal substrate may be such that a two-dimensional diffraction image of the Debye rings obtained by a two-dimensional X-ray detector is obtained as a discontinuous arc-shaped image in which points or line segments are arranged. According to the storage method of the twelfth embodiment, it is possible to more effectively suppress self-discharge and deterioration of an electricity storage device that includes, as a current collector, a metal substrate that has been subjected to a predetermined heat treatment.

[0236] [Thirteenth Form] The thirteenth form is provided as a storage system for storing an electricity storage device. The storage system of the thirteenth form includes a storage unit that houses an electricity storage device including metal atoms that ionize in an electrolyte and participate in charge and discharge, and a metal substrate that forms a current collector, and is configured so that a layer of metal atoms formed by the deposition of the metal atoms is formed on the surface of an electrode during charging, a temperature monitoring unit that monitors the temperature within the storage unit, and a temperature control unit that adjusts the temperature of the electricity storage device housed in the storage unit to maintain it at a predetermined storage temperature of 25°C or higher and 65°C or lower based on the detection result of the temperature monitoring unit. According to the storage system of the thirteenth embodiment, it is possible to suppress the occurrence of self-discharge in the electricity storage device and the deterioration of the electricity storage device. [Explanation of symbols]

[0237] 10, 10A, 10B, 10C, 10D, 10E, 10F, 10G...electricity storage device, 11...container, 12...electrolyte, 15...separator, 16...first electrode chamber, 17...second electrode chamber, 20, 20A, 20B, 20C, 20D, 20E, 20F, 20G...first electrode, 21...current collector, 23, 23A, 23B, 23C, 23D, 23E, 23F, 23G, 23F...metal substrate, 25, 25A, 25B, 25C, 25D...active material layer, 30...second electrode, 31...current collector, 35...active material layer, 40...granular body , 41...particle structure, 43...base, 44...extension, 46...protrusion, 46a...protrusion, 48...surface protrusion, 52...protrusion structure, 52a...first protrusion, 52b...second protrusion, 52c...third protrusion, 100...storage system, 101...storage unit, 102...temperature monitoring unit, 103...temperature control unit, 105...control unit, AC...amorphous carbon layer, VD...cavity, GF...graphene, CN, CNa, CNb, CNc, CNd...carbon nanostructure, CS...uneven structure, CSs...surface uneven structure, MP...metal particle

Claims

1. A method for storing an electricity storage device, comprising: a step of charging the electricity storage device, the electricity storage device comprising: a container filled with an electrolyte; metal atoms that ionize in the electrolyte and participate in charging and discharging; and electrodes disposed in the electrolyte, the electrodes being configured such that, during charging, a layer of the metal atoms is formed on a surface of the electrodes by depositing the metal atoms; a step of opening the charged power storage device and maintaining the temperature of the power storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; The storage method, wherein the electricity storage device has an active material layer of a carbon nanostructure mainly composed of graphene on a plate surface of the metal substrate.

2. The storage method according to claim 1, The storage method, wherein the carbon nanostructures are carbon nanowalls extending from the smooth surface of the metal substrate.

3. The storage method according to claim 1, the surface of the active material layer has a fine uneven structure in which a plurality of fine particles are densely arranged, A storage method in which the carbon nanostructures are arranged over the entire surface of the granular material, extending in elongated shapes outward from the granular material.

4. The storage method according to claim 1, The carbon nanostructure has a base portion formed by stacking the graphene and extending in an elongated manner in the thickness direction of the metal substrate, and a plurality of extension portions made of carbon and extending from the base portion.

5. The storage method according to claim 1, the metal substrate has a plurality of protrusions on the plate surface, A storage method in which, when the metal substrate is viewed in the thickness direction, a plurality of the carbon nanostructures extending linearly on the surface of the metal substrate are distributed on the surface of the metal substrate.

6. The storage method according to claim 1, a fine uneven structure is formed on the surface of the metal substrate, a storage method, wherein an active material layer containing as a main component the carbon nanostructure constituted by the nanographene and amorphous carbon is formed so as to densely cover the surface of the concave-convex structure.

7. A method for storing an electricity storage device, comprising: a step of charging the electricity storage device, the electricity storage device comprising: a container filled with an electrolyte; metal atoms that ionize in the electrolyte and participate in charging and discharging; and electrodes disposed in the electrolyte, the electrodes being configured such that, during charging, a layer of the metal atoms is formed on a surface of the electrodes by depositing the metal atoms; a step of opening the charged power storage device and maintaining the temperature of the power storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; the metal substrate has a plurality of protrusions on a plate surface, on which the lithium atoms are precipitated; The area of ​​the projection region obtained by projecting the convex portion onto the surface of the metal substrate is 10 nm ２ 10000nm or more ２ is as follows: The density of the protrusions on the plate surface is 1 / μm ２ More than 1000 pieces / μm ２ The storage method is as follows.

8. A method for storing an electricity storage device, comprising: a step of charging the electricity storage device, the electricity storage device comprising: a container filled with an electrolyte; metal atoms that ionize in the electrolyte and participate in charging and discharging; and electrodes disposed in the electrolyte, the electrodes being configured such that, during charging, a layer of the metal atoms is formed on a surface of the electrodes by depositing the metal atoms; a step of opening the charged power storage device and maintaining the temperature of the power storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; the metal substrate has a plurality of protrusions on a plate surface, on which the lithium atoms are precipitated; an average value of a maximum length of a projected area obtained by projecting the convex portion onto the plate surface is 10 nm or more and 200 nm or less; A storage method in which the area occupied by the projection area is 1 / 10 or more of the area of ​​the plate surface.

9. A method for storing an electricity storage device, comprising: a step of charging the electricity storage device, the electricity storage device comprising: a container filled with an electrolyte; metal atoms that ionize in the electrolyte and participate in charging and discharging; and electrodes disposed in the electrolyte, the electrodes being configured such that, during charging, a layer of the metal atoms is formed on a surface of the electrodes by depositing the metal atoms; a step of opening the charged power storage device and maintaining the temperature of the power storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; The metal substrate has a fine uneven structure on its plate surface, which is made up of metal particles, has a maximum width of 0.5 μm or more and 30.0 μm or less, and is made up of a plurality of convex bodies on whose surface the lithium atoms precipitate during charging.

10. A method for storing an electricity storage device, comprising: a step of charging the electricity storage device, the electricity storage device comprising: a container filled with an electrolyte; metal atoms that ionize in the electrolyte and participate in charging and discharging; and electrodes disposed in the electrolyte, the electrodes being configured such that, during charging, a layer of the metal atoms is formed on a surface of the electrodes by depositing the metal atoms; a step of opening the charged power storage device and maintaining the temperature of the power storage device at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; A storage method in which a two-dimensional diffraction image of the Debye rings of the metal substrate obtained by a two-dimensional X-ray detector is a discontinuous arc-shaped image in which points or line segments are arranged.

11. A storage method according to any one of claims 1 to 10, The storage temperature is 35°C or higher and 50°C or lower.

12. A storage system for storing an electricity storage device, the storage system comprising: metal atoms that ionize in an electrolyte and participate in charge and discharge; and a metal substrate that constitutes a current collector; and the storage system being configured such that, during charging, a layer of metal atoms formed by the deposition of the metal atoms is formed on a surface of an electrode, a storage unit that accommodates the power storage device; a temperature monitoring unit that monitors the temperature inside the storage unit; a temperature control unit that adjusts the temperature of the power storage device stored in the storage unit based on the detection result of the temperature monitoring unit so as to maintain the temperature at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; The storage system includes a storage device having an active material layer of a carbon nanostructure composed primarily of graphene on a surface of the metal substrate.

13. 13. The storage system of claim 12, A storage system, wherein the carbon nanostructures are carbon nanowalls extending from the smooth surface of the metal substrate.

14. 13. The storage system of claim 12, the surface of the active material layer has a fine uneven structure in which a plurality of fine particles are densely arranged, A storage system in which the carbon nanostructures, extending in elongated strips outward from the granules, are arranged throughout the surface layer of the granules.

15. 13. The storage system of claim 12, The carbon nanostructure has a base portion on which the graphene is laminated and extends in an elongated manner in the thickness direction of the metal substrate, and a plurality of extension portions made of carbon and extending from the base portion.

16. 13. The storage system of claim 12, the metal substrate has a plurality of protrusions on the plate surface, A storage system in which, when the metal substrate is viewed in the thickness direction, a plurality of the carbon nanostructures extending linearly on the surface of the metal substrate are distributed on the surface of the metal substrate.

17. 13. The storage system of claim 12, a fine uneven structure is formed on the surface of the metal substrate, A storage system in which an active material layer mainly composed of the carbon nanostructure made of the nanographene and amorphous carbon is formed so as to densely cover the surface of the uneven structure.

18. A storage system for storing an electricity storage device, the storage system comprising: metal atoms that ionize in an electrolyte and participate in charge and discharge; and a metal substrate that constitutes a current collector; and the storage system being configured such that, during charging, a layer of metal atoms formed by the deposition of the metal atoms is formed on a surface of an electrode, a storage unit that accommodates the power storage device; a temperature monitoring unit that monitors the temperature inside the storage unit; a temperature control unit that adjusts the temperature of the power storage device stored in the storage unit based on the detection result of the temperature monitoring unit so as to maintain the temperature at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; the metal substrate has a plurality of protrusions on a plate surface, on which the lithium atoms are precipitated; The area of ​​the projection region obtained by projecting the convex portion onto the surface of the metal substrate is 10 nm ２ 10000nm or more ２ is as follows: The density of the protrusions on the plate surface is 1 / μm ２ More than 1000 pieces / μm ２ The storage system is as follows.

19. A storage system for storing an electricity storage device, the storage system comprising: metal atoms that ionize in an electrolyte and participate in charge and discharge; and a metal substrate that constitutes a current collector; and the storage system being configured such that, during charging, a layer of metal atoms formed by the deposition of the metal atoms is formed on a surface of an electrode, a storage unit that accommodates the power storage device; a temperature monitoring unit that monitors the temperature inside the storage unit; a temperature control unit that adjusts the temperature of the power storage device stored in the storage unit based on the detection result of the temperature monitoring unit so as to maintain the temperature at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; the metal substrate has a plurality of protrusions on a plate surface, on which the lithium atoms are precipitated; an average value of a maximum length of a projected area obtained by projecting the convex portion onto the plate surface is 10 nm or more and 200 nm or less; A storage system in which the area occupied by the projection area is 1 / 10 or more of the area of ​​the plate surface.

20. A storage system for storing an electricity storage device, the storage system comprising: metal atoms that ionize in an electrolyte and participate in charge and discharge; and a metal substrate that constitutes a current collector; and the storage system being configured such that, during charging, a layer of metal atoms formed by the deposition of the metal atoms is formed on a surface of an electrode, a storage unit that accommodates the power storage device; a temperature monitoring unit that monitors the temperature inside the storage unit; a temperature control unit that adjusts the temperature of the power storage device stored in the storage unit based on the detection result of the temperature monitoring unit so as to maintain the temperature at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; The metal substrate has a fine uneven structure on its plate surface, which is made up of metal particles, has a maximum width of 0.5 μm or more and 30.0 μm or less, and is made up of a plurality of convex bodies on whose surface the lithium atoms precipitate during charging.

21. A storage system for storing an electricity storage device, the storage system comprising: metal atoms that ionize in an electrolyte and participate in charge and discharge; and a metal substrate that constitutes a current collector; and the storage system being configured such that, during charging, a layer of metal atoms formed by the deposition of the metal atoms is formed on a surface of an electrode, a storage unit that accommodates the power storage device; a temperature monitoring unit that monitors the temperature inside the storage unit; a temperature control unit that adjusts the temperature of the power storage device stored in the storage unit based on the detection result of the temperature monitoring unit so as to maintain the temperature at a predetermined storage temperature of 25°C or higher and 65°C or lower; Equipped with the metal atom is a lithium atom, The electrode has a metal substrate that functions as a current collector; The metal substrate is a storage system in which a two-dimensional diffraction image of the Debye rings is obtained by a two-dimensional X-ray detector as a discontinuous arc-shaped image in which points or line segments are arranged.

22. 22. The storage system according to any one of claims 12 to 21, A storage system, wherein the storage temperature is 35°C or higher and 50°C or lower.

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