Power storage device

Abstract

A power storage device 10 includes: an electrolyte 12 containing a lithium imide salt and an organic solvent; a container 11 filled with the electrolyte 12; a positive electrode 30 which includes a compound containing lithium atoms that are ionized in the electrolyte 12 and that are involved in charge and discharge; a negative electrode 20 which is arranged in the electrolyte, includes a metal substrate 23 constituting a collector 21, and is configured so that a layer where the lithium atoms are deposited is formed on the surface of the negative electrode during charging; and a separator 15 which has electric insulation properties, divides the inside of the container 11 into a first electrode chamber 16 where the negative electrode is disposed and a second electrode chamber 17 where the positive electrode 30 is disposed, and transmits lithium ions moving between the first electrode chamber 16 and the second electrode chamber 17.

Description

Energy storage devices

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

[0002] As a chargeable and dischargeable electricity storage device in which lithium ions are involved in charging and discharging, for example, a lithium ion battery as disclosed in Patent Document 1 listed below is known.

[0003] The lithium ion battery of Patent Document 1 includes an anode made of lithium metal foil, a cathode made of a metal oxide material, and an electrolyte solution containing a lithium salt.

[0004] In the lithium-ion battery of Patent Document 1, lithium ions move in the electrolyte during charging and discharging, and charging is achieved by intercalation, in which lithium ions enter between layers of the crystalline electrode material of the cathode.

[0005] In an electricity storage device in which charging is achieved by intercalation at an electrode, such as the lithium ion battery of Patent Document 1, the limit of charge capacity is determined by the number of ions that can intercalate at the electrode. Conventionally, in the technical field of electricity storage devices in which lithium ions are involved in charging and discharging, there has been a demand for a new electrode configuration that can achieve a charge capacity that exceeds the intercalation limit.

[0006] On the other hand, in an electricity storage device using an electrolyte, the battery performance, such as charge capacity, charge rate, charge / discharge efficiency, and durability against repeated charge / discharge, generally depends on the composition of the electrolyte and the concentrations of various components. Therefore, in order to dramatically improve the battery performance of an electricity storage device, it is desirable not only to change the electrode to a new configuration, but also to find a configuration, such as the composition of the electrolyte and the concentrations of various components, that is suitable for the electrode configuration.

[0007] An object of the present application is to provide a novel combination of electrode configuration and electrolyte configuration that can improve battery performance in an electricity storage device that uses lithium ions in charge and discharge.

[0008] The inventors of the present invention have, through extensive research into electricity storage devices, succeeded in developing an electrode that can be charged by an electrode reaction different from intercalation and that can achieve a high charge capacity, and have also succeeded in finding the composition of an electrolyte solution suitable for that electrode. The present invention can be realized, for example, in the following forms.

[0009] One aspect of the present invention is provided as an electricity storage device, comprising: an electrolyte solution containing a lithium imide salt and an organic solvent, a container filled with the electrolyte solution, a positive electrode disposed in the electrolyte solution and having a compound containing lithium atoms that ionize in the electrolyte solution and participate in charge and discharge, a negative electrode disposed in the electrolyte solution and having a metal substrate forming a current collector, the negative electrode configured to form a layer on its surface by deposition of the lithium atoms during charging, and an electrically insulating separator that partitions the interior of the container into a first electrode chamber in which the negative electrode is disposed and a second electrode chamber in which the positive electrode is disposed, and that allows lithium ions to pass between the first electrode chamber and the second electrode chamber.

[0010] This type of electricity storage device includes electrodes configured to be charged by forming a layer of lithium atoms on the surface of the electrodes. This electricity storage device can significantly increase the charge capacity compared to conventional electricity storage devices that charge by intercalation of lithium ions in the electrodes. Furthermore, the inventors of the present invention have independently discovered through experiments using the electrodes that applying an electrolyte containing a lithium imide salt and an organic solvent to an electricity storage device having the electrodes can dramatically improve durability against repeated charge and discharge. This type of electricity storage device includes an electrolyte based on this discovery, making it possible to dramatically increase the charge capacity and durability against repeated charge and discharge compared to conventional configurations.

[0011] The present invention is not limited to lithium-ion batteries, and can be realized in the form of various types of electricity storage devices, such as lithium-ion capacitors. Furthermore, the present invention can also be realized in various forms other than electricity storage devices. For example, the present invention can be realized in the form of an electrolyte solution for an electricity storage device, a combination of electrodes and an electrolyte solution in an electricity storage device, an apparatus or system including an electricity storage device, a manufacturing method for an electricity storage device, a method for charging and discharging an electricity storage device, etc.

[0012] 1 is a schematic diagram showing the configuration of an electricity storage device according to a first embodiment; FIG. 2 is a schematic diagram showing the configuration of a carbon nanostructure according to the first embodiment; FIG. 3 is an explanatory diagram showing an example of the composition of an electrolyte solution according to the first embodiment; FIG. 4 is an explanatory diagram showing a photographed image of carbon nanotubes constituting an active material layer of a negative electrode; FIG. 5 is a first explanatory diagram showing the change in Coulombic efficiency with respect to the number of charge-discharge cycles for Examples and Comparative Examples; FIG. 6 is an explanatory diagram showing the change in end-of-charge voltage with respect to the number of charge-discharge cycles for Examples and Comparative Examples; FIG. 7 is an explanatory diagram showing a Cole-Cole plot during charging for Examples; FIG. 8 is an explanatory diagram showing a Cole-Cole plot during discharging for Examples; FIG. 9 is an explanatory diagram showing a Cole-Cole plot during charging for Comparative Examples; FIG. 10 is an explanatory diagram showing a current-potential curve for Examples; FIG. 11 is an explanatory diagram showing a current-potential curve for Examples; FIG. 12 is an explanatory diagram showing a current-potential curve for Examples; FIG. 13 is an explanatory diagram showing a current-potential curve for Examples; FIG. 14 is an explanatory diagram showing a current-potential curve for Examples; FIG. 15 is an explanatory diagram showing a current-potential curve for Examples; FIG. 16 is an explanatory diagram showing a current-potential curve for Examples; 7 is a seventh explanatory diagram showing current-potential curves of examples. 8 is a diagram showing current-potential curves of examples. An explanatory diagram showing a current-potential curve of a comparative example. A schematic diagram showing a configuration of a first electrode included in an electricity storage device of a second embodiment. An explanatory diagram showing a captured image of an example of the first electrode of the second embodiment. A schematic diagram showing a configuration of a first electrode included in an electricity storage device of a third embodiment. An explanatory diagram showing a captured image of an example of the first electrode of the third embodiment. A schematic diagram showing a configuration of a first electrode included in an electricity storage device of a fourth embodiment. An explanatory diagram showing a captured image of an example of the first electrode of the fourth embodiment. A schematic diagram showing a configuration of a first electrode included in an electricity storage device of a fifth embodiment. An explanatory diagram showing a captured image of an example of the first electrode of the fifth embodiment. An explanatory diagram showing a Raman spectroscopy spectrum of an example of the first electrode of the fifth embodiment. A schematic diagram showing a configuration of an electricity storage device of a sixth embodiment. An explanatory diagram showing a captured image of an example of the metal substrate of the sixth embodiment. 13 is a schematic diagram showing a first example of the configuration of the convex structure portion of the metal substrate of the seventh embodiment; FIG. 14 is a schematic diagram showing a second example of the configuration of the convex structure portion of the metal substrate of the seventh embodiment; FIG. 15 is an explanatory diagram showing a photographed image of an example of the metal substrate of the seventh embodiment; FIG. 16 is a schematic diagram showing the configuration of an electricity storage device of the eighth embodiment; and FIG. 17 is an explanatory diagram showing an example of a change in X-ray diffraction due to heat treatment of the metal substrate of the eighth embodiment.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 a metal substrate according to the eighth embodiment.

[0013] Hereinafter, with reference to the drawings, an embodiment of the electricity storage device according to the present invention and examples of the electricity storage device according to the present invention based on specific experimental examples by the inventors of the present invention will be described.

[0014] 1. First Embodiment 1-1. Configuration of Electricity Storage Device: Fig. 1 is a schematic diagram showing the configuration of an electricity storage device 10 according to a first embodiment. In this embodiment, the electricity storage device 10 is a lithium ion battery in which lithium (Li) ions are involved in charging and discharging, and charging is performed by an electrode reaction described below that is different from intercalation.

[0015] 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. 1, the container 11 is illustrated by a dashed line, and the separator 15 is illustrated by a broken line.

[0016] The container 11 has an internal space filled with the electrolyte solution 12. The container 11 is liquid-tight and made of a material that is not easily reactive with the electrolyte solution 12. The electrolyte solution 12 is made of a solution in which a lithium salt is dissolved in an organic solvent, and has the property of being able to transfer Li ions, which are metal ions involved in charging and discharging, between the first electrode 20 and the second electrode 30. Details of the electrolyte solution 12 will be described again after describing the battery reaction in the electricity storage device 10.

[0017] The separator 15 divides the internal space of the container 11 into a first electrode chamber 16 and a second electrode chamber 17. The first electrode chamber 16 accommodates a first electrode 20, and the second electrode chamber 17 accommodates a 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 Li ions transmitted via the electrolyte solution 12 to pass through. The separator 15 is made of, for example, a resin film or nonwoven fabric having a porous structure.

[0018] The first electrode 20 constitutes a negative electrode. In this embodiment, 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 is formed of a metal foil made of copper (Cu). In this embodiment, the metal substrate 23 has a smooth surface.

[0019] 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. The metal substrate 23 does not have to be made of metal foil, but may be made of, for example, a thin metal plate or a thin metal film. The metal substrate 23 does not have to be made in a flat plate shape, but may be bent into various shapes, such as a cylindrical shape or a corrugated shape.

[0020] 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.

[0021] Fig. 2 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. 2, graphene GF constituting the carbon nanostructure CN is shown in the form of a substantially rectangular sheet.

[0022] Graphene GF as a main component and carbon nanostructures CN are disposed 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.

[0023] In this embodiment, the carbon nanostructure CN has a configuration in which the 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 GFs are stacked in the thickness direction.

[0024] The graphene GF does not have to be entirely composed of single crystals of six-membered carbon rings. In other words, the 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. The graphene GF may have a mosaic structure mainly composed of carbon with a six-membered ring structure. The mosaic structure means a structure in which a plurality of regions composed of six-membered carbon ring structures are discretely arranged.

[0025] The carbon nanostructures CN can be formed by a known CVD (chemical vapor deposition) method on the surface of the metal substrate 23. The CVD method capable of forming the carbon nanostructures CN is described in, for example, Japanese Patent Application Laid-Open No. 2024-016510.

[0026] 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 the 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.

[0027] In this embodiment, the carbon nanostructure CN is composed of carbon nanowalls extending from the smooth surface of the metal substrate 23. The carbon nanowalls have a structure in which graphene GF is stacked in the thickness direction.

[0028] 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.

[0029] 1, 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, an Al metal foil.

[0030] In other embodiments, the current collector 31 may be made of another metal such as titanium (Ti). The current collector 31 may have a form other than a metal foil. The current collector 31 does not have to be formed in a flat shape, and may be bent into various shapes such as a cylindrical shape or a corrugated shape.

[0031] 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 containing Li atoms, which are atoms of metal ions involved in charge and discharge, a conductive additive, and a binder. The active material layer 35 may also contain a thickener.

[0032] As the active material of the second electrode 30, for example, a ternary material can be used, such as lithium cobalt oxide (LiCoO ２ ;LCO), lithium manganese oxide (Li-Mn-Ni-Co-O;LMO), and lithium nickel oxide (Li-Al-Ni-Co-O;NCA) can be used. As the conductive additive, for example, carbon black (CB), carbon nanotubes (CNT), acetylene black (AB), and mixtures thereof can be used. As the binder, for example, polyvinylidene fluoride (PVDF) and styrene butadiene rubber (SBR) can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

[0033] 1-2. Battery Reaction in the Electricity Storage Device: Since the electricity storage device 10 includes the first electrode 20 and the second electrode 30 configured as described above, during charging, Li atoms are precipitated on the surface of the first electrode 20, forming a layer of Li atoms. The electrode reaction during charging and discharging of the electricity storage device 10 of this embodiment can be expressed, for example, by the following reaction formula.

[0034] The positive electrode material is LiCoO ２In this case, the electrode reaction at the second electrode 30, which is the positive electrode, is expressed by the following chemical formula (1): where x represents the proportion of reacting atoms and is a real number greater than 0 and less than 1.

[0035] [Chemical formula 1] Li １－ｘ CoO ２ + xLi ＋ + xe － ⇔ LiCoO ２ …(1)

[0036] In contrast, the electrode reaction at the first electrode 20, which is the negative electrode, is represented by the following chemical formula (2): As shown in chemical formula (2), when the electricity storage device 10 is charged, Li is precipitated on the surface of the first electrode 20, and a Li layer is formed.

[0037] [Chemical formula 2] Li ＋ + e － ⇔ Li … (2)

[0038] The charge capacity of conventional lithium-ion batteries, which are charged by intercalation, where metal ions involved in charging and discharging are inserted into gaps in the crystalline structure of the electrode, is limited by the crystalline structure of the electrode, as this determines the number of ions that can be intercalated.

[0039] In contrast, according to 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, according to the electricity storage device 10 of this embodiment, it is possible to achieve a significantly higher charge capacity than an electricity storage device in which intercalation occurs at the electrodes during charging.

[0040] 1-3. Composition of Electrolyte Solution: Through their own research, the inventors of the present invention have independently discovered that applying the electrolyte solution 12 described below to electrodes 20, 30 configured to be capable of charging and discharging through the electrode reaction described above can dramatically improve the durability of the electricity storage device 10 against repeated charging and discharging. "Durability against repeated charging and discharging" refers to battery performance that allows repeated charging and discharging without significant deterioration in charge and discharge performance. The electrolyte solution 12 provided in the electricity storage device 10 of this embodiment will be described in detail below.

[0041] 3 is an explanatory diagram showing an example of the composition of the electrolyte solution 12 in this embodiment. The electrolyte solution 12 contains the lithium imide salt shown in FIG. 2 and an organic solvent. In this specification, the term "lithium imide salt" refers to a salt having a structure represented by the following chemical formula (3).

[0042] [Chemical Formula 3] LiN(SO ２ R Ａ ) (SO ２ R Ｂ ) … (3)

[0043] In the above chemical formula (3), "R Ａ " and "R Ｂ " represents a fluorine atom (F) or a fluorocarbon. Ａ " and "R Ｂ " may be the same atom or group of the same structure.

[0044] The electrolyte solution 12 preferably contains, as the lithium imide salt, one of the following , , and <c> or one of the three types of derivatives of , , and <c> below. Alternatively, the electrolyte solution 12 preferably contains, as the lithium imide salt, the following , , and <c> or a mixture of any combination of the following derivatives of , , and <c> below.

[0045] [Examples of lithium imide salts] LiN(FSO ２ ) ２ LiN(CF ３ SO ２ ) ２ <c> LiN (SO ２ C２ F ５ ) ２

[0046] The lithium imide salt of (a) is "lithium bis(fluorosulfonyl)imide" and is also written as "LiFSI." The lithium imide salt of (b) is "lithium bis(trifluoromethanesulfonyl)imide" and is also written as "LiTFSI." The lithium imide salt of (c) is "lithium bis(perfluoroethylsulfonyl)imide" and is also written as "LiBETI."

[0047] In the configuration of this embodiment, the electrolyte is not a lithium imide salt but a conventionally used lithium salt, LiPF ６ When using the LiPF ６ However, there is a possibility that the lithium reacts frequently with the Li deposited on the surface of the negative electrode during charging, forming a layer of Li compounds, which may result in an increase in the internal resistance of the electricity storage device.

[0048] In contrast, lithium imide salts such as those described above in (a), (b), and (c) are chemically stable, and therefore, when used in the electrolyte solution 12 of the electricity storage device 10, the occurrence of interactions with Li deposited on the surface of the negative electrode is suppressed, thereby improving battery performance, including durability against repeated charge and discharge.

[0049] The electrolyte solution 12 of this embodiment contains LiFSI () among the lithium imide salts , , and <c> described above. The reason LiFSI was selected in this embodiment is that it tends to have higher ionic conductivity and lower viscosity than LiTFSI and LiBETI at typical concentrations, making it more likely to be effective in battery reactions. Furthermore, LiFSI contains fewer fluorine atoms, which is presumably more likely to suppress reaction with Li atoms deposited on the negative electrode surface than LiTFSI or LiBETI.

[0050] For reference, the ionic conductivity σ of LiTFSI is approximately 3.0 to 10.0 mS cm at a concentration of 1 to 3 mol / L. －１In contrast, the ionic conductivity σ of LiFSI is approximately 9.0 to 13.0 mS cm －１ Furthermore, the viscosity η of LiTFSI is approximately 2.5 to 16.5 cP at a concentration of 1 to 3 mol / L, whereas the viscosity η of LiFSI is approximately 2.4 to 9.0 cP. 1.0 cP can be converted to 1.0 mPa·s.

[0051] The concentration of LiFSI in the electrolyte solution 12 is preferably, for example, 4.0 mol / L or more and 6.0 mol / L or less. The concentration of LiFSI in the electrolyte solution 12 is more preferably 4.5 mol / L or more and 5.5 mol% or less. The concentration of LiFSI in the electrolyte solution 12 is even more preferably about 5.0 mol / L. In this specification, when a numerical value is accompanied by "about," it means that an error range of ±5% is included.

[0052] The electrolyte solution 12 preferably contains, as the organic solvent, one of the following five types of organic solvents <d>, <e>, <f>, <g>, and <h>, or derivatives of each of the following types of organic solvents <d>, <e>, <f>, <g>, and <h>, as a main component. Alternatively, the electrolyte solution 12 may contain, as the organic solvent, a mixed solution of any combination of the following five types of organic solvents <d>, <e>, <f>, <g>, and <h>, or derivatives of each of the following types of organic solvents <d>, <e>, <f>, <g>, and <h>, as a main component. In this specification, the term "main component" refers to a component having a mass content of 50% or more.

[0053] [Examples of organic solvents] <d> 1,2-dimethoxyethane (DME, C ４ H １０ O ２ ) <e> 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE, C ５ H ４ F ８ O) <f> 1,2-diethoxyethane (DEE, C ６ H １４ O ２ ) <g> Triglyme (Triglyme, CH ３ OCH ２ CH ２ OCH ２ CH２ OCH ２ CH ２ OCH ３ ) <h> Tetraglyme (dimethoxytetraethylene glycol tetraglyme, C １０ H ２２ O ５ )

[0054] The electrolyte solution 12 of this embodiment contains DME as the main component of the organic solvent. By using DME as the main component of the organic solvent, it is possible to further increase the durability of the electricity storage device 10 against repeated charge and discharge. This is because DME has a higher solubility of lithium imide salts such as LiFSI than TTE, triglyme, and tetraglyme, and a strong solvation effect with Li ions is obtained. In addition, DME has a moderate boiling point that is higher than that of DEE.

[0055] In the present embodiment, the volume content of DME in the organic solvent in the electrolytic solution 12 is preferably 90% or more and 100% or less. The organic solvent in the electrolytic solution 12 may be composed of DME alone, or may contain DME as the main component and any of the organic solvents listed in (e), (f), (g), and (h) above.

[0056] It is more preferable that the electrolyte solution 12 contains, as an organic solvent, TTE (e) in addition to DME (d). Because TTE has a relatively low solubility for lithium imide salts such as LiFSI, in this embodiment, TTE is not the main organic solvent of the electrolyte solution 12, but is used as a second solvent added to the main first solvent. Adding TTE to the electrolyte solution 12 as the second solvent strengthens the solvation of Li in the electrolyte solution 12, thereby improving the oxidation stability of the electrolyte solution 12. This further enhances the durability of the electricity storage device 10 against repeated charge and discharge cycles.

[0057] The volume content of TTE as the second solvent in the electrolytic solution 12 may be 0.1% or more and 5.0% or less, and the remaining component in the organic solvent may be DME. The volume content of TTE in the organic solvent in the electrolytic solution 12 is more preferably 0.5% or more, and even more preferably 1.0% or more.

[0058] In other embodiments, the organic solvent of the electrolyte solution 12 may be composed solely of DEE, or may be composed of a first solvent mainly composed of DEE and TTE added as a second solvent. In addition to the first and second solvents, the organic solvent of the electrolyte solution 12 may further contain a third or fourth solvent. The type of organic solvent contained in the electrolyte solution 12 may be appropriately selected depending on the type of lithium imide salt. Therefore, in other embodiments, the first solvent of the electrolyte solution 12 may be any of TTE, DEE, triglyme, and tetraglyme, or another organic solvent may be used. Furthermore, the organic solvent of the electrolyte solution 12 may be a mixture of multiple solvents with a volume content of 50% or less.

[0059] In addition to the lithium imide salt and organic solvent, an additive may be added to the electrolyte solution 12. For example, the additives listed below can be used. The additive may be added at a concentration of 0.1% by mass or more and 2.0% by mass or less.

[0060] [Examples of additives] Vinylene carbonate (VC), lithium nitrate (LiNO ３ ), boroxine compounds including triisopropoxyboroxine (TiPBx), derivatives thereof, and mixtures of any combinations thereof, etc.

[0061] As will be shown in the examples described later, the addition of an additive can increase the current range obtained by cyclic voltammetry, thereby further improving the battery performance of the electricity storage device 10.

[0062] 1-4. Summary of the First Embodiment As described above, according to the electricity storage device 10 of this embodiment, a layer of Li is formed on the surface of the first electrode 20 during charging, making it possible to increase the charge capacity compared to electricity storage devices in which charging is achieved by intercalation at the electrode. Furthermore, according to the electricity storage device 10 of this embodiment, the electrolyte solution 12 containing a lithium imide salt and an organic solvent is used, making it possible to dramatically improve durability against repeated charge and discharge, as shown in the following examples.

[0063] 1-5. Examples of Electricity Storage Device: Examples of the electricity storage device 10 of the first embodiment will be described below with reference to the drawings and tables.

[0064] (1) Configuration of the electricity storage devices of Examples and Comparative Examples: The electricity storage devices of Examples E1 to E8 and Comparative Examples C1 and C2 were fabricated as lithium ion battery coin cells with the configurations described below. Table 1 below summarizes the configurations of the negative electrodes and electrolyte solutions in the electricity storage devices of Examples E1 to E8 and Comparative Examples C1 and C2.

[0065]

[0066] [Configuration of Negative Electrode] In Examples E1 to E8 and Comparative Example C1, the metal substrate serving as the current collector of the first electrode (negative electrode) was made of Cu foil. In Examples E1 to E8 and Comparative Example C2, the active material layer was made of carbon nanowalls (CNW). Only in Comparative Example C2, the negative electrode current collector was made of Li foil, and no active material layer was provided.

[0067] The CNWs constituting the negative electrode active material layers of Examples E1 to E8 and Comparative Example C1 were formed on the smooth surface of Cu foil 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 refers to the pressure inside the treatment chamber. The "heating temperature" in Table 2 refers to 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.

[0068]

[0069] 4 shows photographed images I1a, I1b, and I1c showing the negative electrodes of Examples E1 to E8 and Comparative Example C1. Photographed image I1a is an image of the current collector and active material layer viewed with a scanning electron microscope in a direction perpendicular to the thickness direction of the electrode. Photographed image I1b is an image of the active material layer viewed with a scanning electron microscope in the thickness direction of the electrode. Photographed image I1c is an image of the surface of the negative electrode after charging is completed, viewed with a scanning electron microscope in a direction perpendicular to the thickness direction of the electrode.

[0070] As shown in the photographed images I1a and I1b, the CNWs constituting the active material layers of the negative electrodes of Examples E1 to E8 and Comparative Example C1 were formed with a substantially uniform height of about 1.0 μm. As shown in the photographed image I1c, after charging of Example E1, a layer of CNWs with a thickness of T Ｌｉ A layer of Li atoms was formed. This layer of Li atoms was formed by the electrode reaction represented by the above chemical formula (2). It was also confirmed that a layer of Li atoms was similarly formed during charging in other Examples E2 to E8 and Comparative Example C1.

[0071] [Configuration of Electrolyte Solutions in Examples] The electrolyte solutions of Examples E1 to E8 used LiFSi with a concentration of 5 mol / L as the lithium imide salt. The electrolyte solution of Example E1 used an organic solvent containing 100% DME by volume. The electrolyte solution of Example E2 used an organic solvent containing 99.5% DME by volume and 0.5% TTE by volume. The electrolyte solution of Example E3 used an organic solvent containing 99.0% DME by volume and 1.0% TTE by volume. The electrolyte solution of Example E4 used an organic solvent containing 98.0% DME by volume and 2.0% TTE by volume. The electrolyte solution of Example E5 used an organic solvent containing 97.0% DME by volume and 3.0% TTE by volume. The electrolyte solution of Example E6 used an organic solvent containing 95.0% by volume of DME and 5.0% by volume of TTE. The electrolyte solution of Example E7 used an organic solvent containing 100% by volume of DME and 1.0% by mass of LiO as an additive. ３In the electrolytic solution of Example E8, an organic solvent containing 100% DME by volume was used, and VC was added as an additive at a concentration of 0.25% by mass.

[0072] [Configuration of the Electrolyte Solution of Comparative Examples] The electrolyte solution of Comparative Example C1 contained LiPF 5 with a concentration of 5 mol / L as a lithium salt. ６ The electrolyte solution of Comparative Example C2 used LiFSI at a concentration of 5 mol / L as the lithium imide salt, and DME at a volume content of 100% as the organic solvent.

[0073] [Other Configurations of Examples and Comparative Examples] Other configurations of Examples E1 to E8 and Comparative Examples C1 and C2 are shown in Table 3 below.

[0074]

[0075] (2) Evaluation of charge-discharge cycle characteristics based on Coulombic efficiency: Figures 5 and 6 are explanatory diagrams showing the evaluation results of charge-discharge cycle characteristics based on Coulombic efficiency for Examples E1 and E3 and Comparative Examples C1 and C2. "Charge-discharge cycle characteristics" refers to characteristics of an electricity storage device that indicate its durability against repeated charge and discharge. It can be said that the higher the durability against repeated charge and discharge of an electricity storage device, the better the charge-discharge cycle characteristics.

[0076] To evaluate the charge-discharge cycle characteristics, Examples E1 and E3 and Comparative Examples C1 and C2 were repeatedly charged and discharged under the conditions described below, and the Coulombic efficiency of each cycle was measured. In this evaluation test, the minimum number of cycles at which the Coulombic efficiency no longer exceeded 80% after repeated charging and discharging was determined as an index of charge-discharge cycle characteristics. Hereinafter, this minimum number of cycles will also be referred to as the "critical cycle number." The higher the critical cycle number, the better the charge-discharge cycle characteristics.

[0077] 5 shows the results of measuring the coulombic efficiency of Example E1 and Comparative Example C1. As shown in Table 1 above, Example E1 and Comparative Example C1 had the same negative electrode configuration, and both had active material layers composed of CNW. However, Example E1 and Comparative Example C1 had different electrolyte configurations. As shown in Table 1, the electrolyte of Example E1 contained LiFSI as a lithium imide salt, whereas the electrolyte of Comparative Example C1 did not contain a lithium imide salt but contained LiPF ６ had the following characteristics:

[0078] The charge-discharge cycle conditions in this evaluation test are as follows: In the following, "CC" is an abbreviation for "Constant Current", and "CC-CV" is an abbreviation for "Constant Current-Constant Voltage".

[0079] <Conditions for charge / discharge cycles for initializing the power storage device> Charge (CC): Charge to 5 mAh at a constant current of 1 mA. Discharge (CC): Discharge to 4 mAh at a constant current of 1 mA.

[0080] <Charge-discharge cycle conditions for characteristic evaluation> Charging (CC-CV): Charged at a constant current of 1 mA up to a cutoff voltage of 4.95 V, then charged to a capacity of 2 mAh (approximately 1.5 mAh / cm) at a constant voltage of 4.95 V. ２ ) Charge to a cutoff voltage of 2.0 V. Discharge (CC): Discharge at a constant current of 1 mA to a cutoff voltage of 2.0 V.

[0081] The limit number of cycles for Example E1 exceeded 300, recording 304. On the other hand, the limit number of cycles for Comparative Example C1 did not exceed 100, remaining at 88. Thus, there is a difference of more than three times between the results for Example E1 and Comparative Example C1, and this difference can be said to be significant enough to exceed the predictions of a person skilled in the art.

[0082] This result indicates that, as in Example E1, by using an electrolyte solution containing a lithium imide salt and an organic solvent in an energy storage device in which a layer of Li atoms is formed on the surface of the negative electrode during charging, the charge-discharge cycle characteristics can be dramatically improved. On the other hand, as in Comparative Example C1, even if an active material layer composed of CNW is provided on the negative electrode, when an electrolyte solution not containing a lithium imide salt is used, the charge-discharge cycle characteristics are difficult to improve. Furthermore, the result of Example E1 indicates that at least LiFSI is preferable as an example of the lithium imide salt of the electrolyte, and DME is preferable as an example of the main component of the organic solvent.

[0083] FIG. 6 shows the measurement results for Examples E1, E3, and Comparative Example C2. As shown in Table 1 above, Examples E1 and E3 have the same negative electrode configuration, but the organic solvent configuration in the electrolyte is different. The organic solvent in Example E1 was composed only of DME, while the organic solvent in Example E3 had a configuration in which TTE was added to the main component DME. In the organic solvent in Example E3, the volume content of DME was 99.0%, and the volume content of TTE was 1.0%. Comparative Example C2 had a configuration in which the negative electrode current collector was composed of Li foil, and the electrolyte configuration was the same as Example E1.

[0084] The conditions for the charge-discharge cycle in this evaluation test are as follows:

[0085] <Conditions for charge / discharge cycles for initializing the power storage device> Charge (CC): Charge to 5 mAh at a constant current of 1 mA. Discharge (CC): Discharge to 4 mAh at a constant current of 1 mA.

[0086] <Charge-discharge cycle conditions for characteristic evaluation> Charging (CC-CV): Charged at a constant current of 1 mA up to a cutoff voltage of 4.75 V, then charged to a capacity of 4 mAh (approximately 3 mAh / cm) at a constant voltage of 4.75 V. ２ ) Charge to the cutoff voltage of 3.5V. Discharge (CC): Discharge at a constant current of 1mA to the cutoff voltage of 3.5V.

[0087] The limit number of cycles for Example E1 exceeded 100, recording 132 cycles. The limit number of cycles for Example E3 also exceeded 100, recording approximately 120 cycles. On the other hand, the limit number of cycles for Comparative Example C2 did not exceed 100, recording only 63 cycles. The results for Examples E1 and E3 and Comparative Example C2 differed by a factor of approximately two or more, and this difference was significant enough to exceed the predictions of those skilled in the art.

[0088] The results of Fig. 6 show that in an electricity storage device of a type in which charging is achieved by intercalation, such as Comparative Example C2, the charge-discharge cycle characteristics are difficult to improve even when the same electrolyte solution as in Example E1 is used. Considering both the results of Fig. 5 and Fig. 6 above, it can be seen that an electrolyte solution containing a lithium imide salt is suitable for improving the charge-discharge cycle characteristics of an electricity storage device of a type in which a Li metal layer is formed on the negative electrode during charging, such as in Examples E1 and E3.

[0089] In Example E3, in which TTE was added to the organic solvent of the electrolyte, the coulombic efficiency was higher and more stable over almost all cycles than in Example E1, in which the organic solvent was composed solely of DME. This result shows that adding TTE to the DME organic solvent of the electrolyte can further improve and stabilize the charge / discharge efficiency of the electricity storage device.

[0090] (2) Evaluation of charge-discharge cycle characteristics based on charge completion voltage: Figure 7 shows a graph illustrating the change in charge completion voltage when charge and discharge were repeated for Example E1 and Comparative Example C1. In this specification, "charge completion voltage" means the voltage of the power storage device when fully charged. In this evaluation test, after performing charge-discharge cycles under the conditions for initialization described above, one cycle of charge and discharge was repeated under the conditions below, and the charge completion voltage for each cycle was measured.

[0091] <Charge-discharge cycle conditions> Charging (CC): 2 mAh (approximately 1.5 mAh / cm) at a constant current of 1 mA up to a cutoff voltage of 4.95 V ２ ) Charge to. Discharge (CC): Discharge at a constant current of 2 mA.

[0092] In Example E1, the charge completion voltage increased gradually as the number of charge-discharge cycles increased, whereas in Comparative Example C1, the charge completion voltage increased at a steeper rate than in Example E1 from the initial number of cycles, and then increased at an even steeper rate after the number of cycles exceeded 40.

[0093] The gradual increase in the charge completion voltage in Example E1 indicates that Example E1 maintains a more stable charge / discharge state and has improved charge / discharge cycle characteristics than Comparative Example C1. In contrast, the sudden increase in the charge completion voltage in Comparative Example C1 indicates the low durability of Comparative Example C1 when charge / discharge is repeated, and indicates that the charge / discharge cycle characteristics of Comparative Example C1 are significantly inferior to those of Example E1.

[0094] Thus, in the evaluation test of charge-discharge cycle characteristics based on the charge completion voltage, it was shown that the charge-discharge cycle characteristics can be improved by using an electrolyte containing a lithium imide salt in an electricity storage device in which a Li metal layer is formed on the negative electrode during charging. Furthermore, the results of Example E1 show that at least LiFSI is preferred as an example of the lithium imide salt of the electrolyte, and at least DME is preferred as an example of the main component of the organic solvent of the electrolyte.

[0095] (3) Evaluation by AC Impedance Method: Figures 8A, 8B, 9A, and 9B show Cole-Cole plots obtained by AC impedance method for Example E1 and Comparative Example C1, respectively. Figure 8A shows the plot of Example E1 during charging, and Figure 8B shows the plot of Example E1 during discharging. Figure 9A shows the plot of Comparative Example C1 during charging, and Figure 9B shows the plot of Comparative Example C1 during discharging.

[0096] In Example E1, the resistance R of the semicircular portion was ｃｔ This indicates that in Example E1, the internal resistance of the positive electrode is significantly lower than that of Comparative Example C1, the charge-discharge cycle characteristics are significantly improved, and durability against repeated charge-discharge cycles is dramatically improved.

[0097] In Example E1 and Comparative Example C1, the diffusion resistor R extending from the right end of the semicircular portion ｄｉｆ The diffusion resistance R in Example E1 and Comparative Example C1 was significantly different. ｄｉｆ This difference indicates that the Li ions are more easily transferred in the electrolyte solution of Example E1, which indicates that the charge / discharge efficiency of Example E1 is improved compared to that of Comparative Example C1.

[0098] In addition, during charging in Example E1, the semicircular portion is connected to the resistor R ＳＥＩ It was confirmed that the resistance Rct was divided into a solid electrolyte interphase (SEI) layer and a resistance Rct. This indicates that an SEI (Solid Electrolyte Interphase) layer was formed at the boundary between the electrolyte and the negative electrode during charging in Example E1. The formation of the SEI layer leads to stabilization of charging performance. In Comparative Example C1, no signs of the formation of such an SEI layer were observed. Thus, it can be seen that the combination of the negative electrode and the electrolyte in Example E1 results in the formation of an SEI layer during charging, thereby improving charging performance.

[0099] As described above, the evaluation results of Example E1 by the AC impedance method indicate that the charge / discharge characteristics of an electricity storage device in which a Li metal layer is formed on the negative electrode during charging can be improved by using an electrolyte solution containing a lithium imide salt. The results of Example E1 also indicate that at least LiFSI is preferred as an example of the lithium imide salt of the electrolyte solution, and at least DME is preferred as an example of the main component of the organic solvent of the electrolyte solution.

[0100] (4) Evaluation by Cyclic Voltammetry: FIGS. 10 to 18 show current-potential curves obtained by cyclic voltammetry (CV) for Examples E1 to E8 and Comparative Example C1, respectively.

[0101] Table 4 below shows the maximum voltage V obtained by the CV method for Examples E1 to E8 and Comparative Example C1. ｍａｘ , maximum current I １ , minimum current I ２ , and the current range I １ -I２ The remarks for Examples E2 to E8 in Table 4 indicate differences from the electrolyte solution of Example E1.

[0102]

[0103] Please refer to Figures 10 and 18. Figure 10 shows the current-potential curve obtained in Example E1, and Figure 18 shows the current-potential curve obtained in Comparative Example C1.

[0104] In Comparative Example C1, almost no potential window is formed in the current-potential curve, whereas in Example E1, a wide potential window is formed in the current-potential curve, which indicates that in Example E1, the organic solvent of the electrolyte is not easily oxidized or reduced during charge and discharge, and that durability is high when charge and discharge are repeated.

[0105] Furthermore, in the current-potential curve of Example E1, when the applied voltage was increased, the increase in current was suppressed up to about 4.0 V, and the current showed a tendency to increase significantly after about 4.0 V. This tendency indicates that oxidation of the positive electrode material during charge and discharge is suppressed in Example E1, and that durability is high when charge and discharge are repeated.

[0106] The only difference between Example E1 and Comparative Example C1 was the composition of the electrolyte solution. In other words, the evaluation results of Example E1 and Comparative Example C1 by the CV method show that the charge-discharge cycle characteristics are significantly improved by applying an electrolyte solution containing a lithium imide salt and an organic solvent to an electricity storage device in which a layer of Li atoms is formed on the surface of the negative electrode during charging.

[0107] In addition to Figure 10, Figures 11, 12, 13, 14, and 15 are referred to. Figures 11, 12, 13, 14, and 15 show current-potential curves obtained in Examples E2, E3, E4, E5, and E6, respectively. As shown in Tables 1 and 4, Examples E2, E3, E4, E5, and E6 each have substantially the same configuration as Example E1, except that TTE was added to the organic solvent of the electrolyte solution.

[0108] The current-potential curves of Examples E2, E3, E4, E5, and E6 all exhibit similar characteristics to the current-potential curve of Example E1 described above, such as the potential window and the tendency of current change when the applied current is increased. The results shown in Figures 11 to 15 reveal that, as an organic solvent for an electrolyte solution of an electricity storage device in which a layer of Li atoms is formed on the surface of the negative electrode during charging, a configuration in which TTE is added to DME, which is the main component, is one suitable example that can improve the charge-discharge cycle characteristics.

[0109] From the results of Examples E2, E3, E4, E5, and E6, it is found that it is preferable that the volume content of TTE in the organic solvent is 0.5% or more and 5.0% or less, and the remainder is DME. １ -I ２ This result shows that the volume content of TTE in the organic solvent is more preferably greater than 0.5%, and even more preferably 1.0% or greater.

[0110] Please refer to Figures 16 and 17 in addition to Figure 10. Figures 16 and 17 show current-potential curves obtained in Examples E7 and E8, respectively. As shown in Tables 1 and 4, Examples E7 and E8 each have substantially the same configuration as Example E1, except that an additive was added to the electrolyte solution.

[0111] In both Examples E7 and E8, the current range I １ -I ２ From this result, it is preferable to add an additive to the electrolyte solution, and the additive is LiO ３ , or VC is one of the preferred examples. １ -I ２ was increased to more than twice that of Example E1. From the results of Example E8, it can be seen that VC is more preferable as an additive to be added to the electrolyte.

[0112] LiO in the electrolyte of Example E7 ３ The concentration of LiO in the electrolyte is 1.0 g mass%. ３The concentration of is preferably 0.5 g wt % or more and 1.5 g wt % or less, and more preferably 0.8 g wt % or more and 1.2 g wt % or less.

[0113] The VC concentration in the electrolyte solution of Example E8 was 0.25 g wt %. From this, it can be said that the VC concentration in the electrolyte solution is preferably 0.20 g wt % to 0.30 g wt %, and more preferably 0.22 g wt % to 0.28 g wt %.

[0114] 1-6. Summary: As described above, in Examples E1 to E7, significant improvements were obtained in battery performance, such as charge / discharge cycle characteristics, compared to Comparative Examples C1 and C2, exceeding the expectations of those skilled in the art. This result demonstrates that the energy storage device 10 of the first embodiment can achieve the various effects described above.

[0115] 2. Second embodiment: Fig. 19 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20A included in an electricity storage device 10A according to a second embodiment. Fig. 19 illustrates a cross-sectional structure of the first electrode 20A taken along an arbitrary cross section along the thickness direction.

[0116] The power storage device 10A of the second embodiment has almost the same configuration as the power storage device 10 of the first embodiment, except for the configuration of the first electrode 20A. 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.

[0117] The surface of the first electrode 20A has a fine uneven structure in which a plurality of minute particles 40 constituting 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.

[0118] 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.

[0119] Carbon nanostructures CNa are formed over the entire surface layer of the granules 40. The carbon nanostructures CNa are made of graphene GF as described in FIG. 2 and extend in elongated shapes 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.

[0120] The 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.

[0121] 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 having 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, applying a voltage with the electrode plate as the anode and the base material of the metal substrate 23A as the cathode, and thereby precipitating metal ions contained in the electrode plate onto the surface of the base material of the metal substrate 23A.

[0122] The carbon nanostructures CNa are formed by a plasma treatment by 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 hydrogen (H ２ ) and a reaction contributing gas such as argon (Ar) are used.

[0123] 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 radicals generated in the plasma form carbon nanostructures CNa on the surface of the metal substrate 23A.

[0124] The power storage device 10A of the second embodiment has the first electrode 20A configured as 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 power 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.

[0125] The average particle size of the granules 40 in the first electrode 20A is preferably 0.1 μm to 10.0 μm, more preferably 0.5 μm to 5.0 μm, and even more preferably 1.0 μm to 3.0 μm. 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.

[0126] 20 shows photographed images I2a, I2b, I2c, and I2d illustrating an example of the first electrode 20A of the second embodiment. The photographed direction of the photographed images I2a and I2c is a direction perpendicular to the thickness direction of the metal substrate 23A, and the photographed direction of the photographed images I2b and I2d is the thickness direction of the metal substrate 23A.

[0127] The captured images I2a and I2b show the surface of the metal substrate 23A before the carbon nanostructures CNa were formed. In this example, the metal substrate 23A in the captured images I2a and I2b is a Cu foil. The surface of the metal substrate 23A had an uneven structure in which particle structures 41, each of which was made of metal particles MP gathered in clusters, were densely arranged.

[0128] 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.

[0129]

[0130] 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 Example E1 in Table 1 described in the first embodiment and the conditions of Table 3. In this lithium-ion battery, during charging, a layer of Li was formed on the granules 40 of the first electrode 20A due to the electrode reaction of chemical formula (2) described in the first embodiment, and it was confirmed that the battery performance was improved compared to a type of electricity storage device that is charged by intercalation.

[0131] The power storage device 10A of the second embodiment shares the same electrode reaction for charging and discharging as the power storage device 10 of the first embodiment. Even in the power storage device 10A of the second embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the power storage device 10A of the second embodiment can achieve various effects similar to those described in the first embodiment.

[0132] 21 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20B included in an electricity storage device 10B according to a third embodiment. Fig. 21 illustrates a cross-sectional structure of the first electrode 20B taken along an arbitrary cross section along the thickness direction.

[0133] The power storage device 10B of the third embodiment has almost the same configuration as the power storage device 10 of the first embodiment, except for the difference in the configuration of the active material layer 25B of the first electrode 20B. 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.

[0134] 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. By forming the amorphous carbon layer AC in a good condition, the state of formation of the carbon nanostructures CNb is improved.

[0135] 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.

[0136] The carbon nanostructure CNb has a base 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 43. Most of the extension portions 44 are formed so as to branch out in a branch-like manner on the upper end side of the base 43.

[0137] 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. 2, 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.

[0138] 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.

[0139] The height of the carbon nanostructures 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 nanostructures CNb is preferably 0.5 μm or more, and more preferably 0.8 μm or more. Furthermore, the height of the carbon nanostructures CNb is further preferably 1.0 μm or more, and even more preferably 1.2 μm or more.

[0140] However, the taller the carbon nanostructures CNb, the longer the time required to form them. Therefore, from the viewpoint of increasing 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 of the carbon nanostructures CNb 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.

[0141] Details of the manufacturing method of 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 radical-injection plasma-enhanced (RI-PE) CVD and capacitively coupled plasma (CPP) CVD.

[0142] To fabricate carbon nanostructures CNb, a first plasma treatment is performed using the RI-PECVD method. In this first plasma treatment, microwaves having a frequency of 2.00 to 3.00 GHz are generated at 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, approximately 0.5 to 1.5 Pa.

[0143] While the source gas is being supplied to the reaction chamber, a high-frequency voltage having a frequency 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.

[0144] 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 source 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.

[0145] 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, thereby forming a plurality of extensions 44 on the surface of each base 43 formed on the metal substrate 23B.

[0146] The power 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 power storage device 10A is charged, Li, which is involved in charging and discharging, precipitates on the carbon nanostructures CNb that constitute the active material layer 25B of the first electrode 20, forming a layer of Li. Li precipitates in the gaps between the base portions 43 of the carbon nanostructures CNb and in the gaps between the extension portions 44, and also precipitates above the carbon nanostructures CNb to form a layer.

[0147] 22 shows images I3a, I3b, I3c, and I3d illustrating an example of the active material layer 25B according to the third embodiment. The images I3a and I3c were taken in the thickness direction, while the images I3b and I3d were taken in a direction perpendicular to the thickness direction of the metal substrate 23B. The metal substrate 23B in this example is a Cu foil.

[0148] The photographed images I3a and I3b shown on the left side of Fig. 22 show a first state in which base 43 of carbon nanostructure CNb has been formed. The photographed images I3c and I3d shown on the right side of Fig. 22 show a second state in which extensions have been formed on the surface of base 43. Table 6 below shows the processing conditions for the first plasma treatment (RI-PECVD) for forming base 43 and the processing conditions for the second plasma treatment (CCP-CVD) for forming extension 44.

[0149]

[0150] A lithium-ion battery coin cell was fabricated using the active material layer 25B shown in images I3c and I3d under the conditions of Example E1 in Table 1 and Table 3 described in the first embodiment. In this lithium-ion battery, Li precipitated on the first electrode 20B during charging due to the electrode reaction of chemical formula (2) described in the first embodiment. Li precipitated in the gaps between the base portions 43 and the extension portions 44 of the carbon nanostructures CNb, and also precipitated above the carbon nanostructures CNb to form a layer. Experiments by the inventors of the present invention confirmed that this lithium-ion battery exhibited improved battery performance compared to power storage devices that charge by intercalation.

[0151] The power storage device 10B of the third embodiment shares the same electrode reaction for charging and discharging as the power storage device 10 of the first embodiment. Even in the power storage device 10B of the third embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the power storage device 10B of the third embodiment can achieve various effects similar to those described in the first embodiment.

[0152] 23 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20C included in an electricity storage device 10C according to a fourth embodiment. Fig. 23 illustrates a cross-sectional structure of the first electrode 20C taken along an arbitrary cross section along the thickness direction.

[0153] The power storage device 10C of the fourth embodiment has substantially the same configuration as the power storage device 10 of the first embodiment, except for the configuration of the first electrode 20C. The first electrode 20C of the power storage device 10C has a metal substrate 23C having a plurality of protrusions 46 on the plate surface.

[0154] 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 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.

[0155] In order 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, the term "particle diameter" refers to the maximum value of the 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.

[0156] In order to realize an appropriate distribution density of the convex portions 46, the distribution density of the metal particles MP in the metal substrate 23C should be 1 particle / μm ２ More than 1000 pieces / μm ２ Here, the "distribution density of metal particles MP" 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.

[0157] 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 to 300 nm. 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.

[0158] 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 described in Fig. 2 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.

[0159] The carbon nanostructure CNc preferably includes a carbon nanotube-like structure in which a graphene sheet is rolled into a cylindrical shape. The carbon nanostructure CNc is a graphite-like substance, and therefore has higher electrical conductivity than carbon materials such as activated carbon.

[0160] 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.

[0161] 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 Figure 24, 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 a region above the protrusions 46.

[0162] 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 generated by plasma treatment of the metal substrate 23C on which the protrusions 46 have been formed by the CPP-CVD method.

[0163] 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.

[0164] 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 the 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.

[0165] 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 re-adhere to the metal substrate 23C. This forms the convex portions 46 composed of the metal particles MP described above. The processing time for this plasma treatment is, for example, about 5 to 15 minutes.

[0166] 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 to a temperature of, for example, 600 to 800° C. by a heater. Then, methane (CH ４ ) and hexafluoroethane (C ２ F ６ ) and carbon-based gases such as H ２ A source gas containing a carbon-based gas and a reaction contributing gas such as Ar is supplied. 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.

[0167] In this state, a high-frequency voltage of, for example, 300 to 700 W and a frequency of 12 to 15 MHz 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.

[0168] 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, precipitates 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.

[0169] 24 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 convex portions 46 of the metal substrate 23C in the captured image I4 and the processing conditions of the plasma processing for forming the carbon nanostructures CNc are shown in Table 7 below.

[0170]

[0171] A lithium-ion battery coin cell was fabricated using the first electrode 20C shown in photographed image I4 under the conditions of Example E1 in Table 1 and Table 3 described in the first embodiment. During charging, this lithium-ion battery formed a layer of Li on the surface of the first electrode 20C due to the electrode reaction of chemical formula (2) described in the first embodiment. It was also confirmed that this lithium-ion battery exhibited improved battery performance compared to power storage devices that are charged by intercalation.

[0172] The power storage device 10C of the fourth embodiment shares the same electrode reaction for charging and discharging as the power storage device 10 of the first embodiment. Even in the power storage device 10C of the fourth embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the power storage device 10C of the fourth embodiment can achieve various effects similar to those described in the first embodiment.

[0173] 25 is a schematic cross-sectional view illustrating a cross-sectional structure of a first electrode 20D included in an electricity storage device 10D according to a fifth embodiment. Fig. 25 illustrates a cross-sectional structure of the first electrode 20D taken along an arbitrary cross section along the thickness direction.

[0174] The power storage device 10D of the fifth embodiment has almost the same configuration as the power storage device 10 of the first embodiment, except that it includes a first electrode 20D with a different configuration. The first electrode 20D has a configuration in which an active material layer 25D is formed on the surface of a metal substrate 23D.

[0175] A microscopic uneven structure CS 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.

[0176] 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 the surface of the active material layer 25D has a dense distribution of multiple granular surface protrusions 48 with a width of 0.1 μm or more and 10.0 μm or less 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 each 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 process.

[0177] The active material layer 25D is primarily composed of a carbon nanostructure CNd composed of nanographene and amorphous carbon. The active material layer 25D is configured by depositing nanographene and amorphous carbon particles. 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. Hydroxyl groups may remain inside the active material layer 25D as impurities introduced during the manufacturing process.

[0178] 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 alcohols 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.

[0179] The alcohol contained in the solution is, for example, ethanol (C ２ H ６Ｏ The reaction gas may be, for example, Ar or H ２In the plasma processing, the reaction 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 in the reaction chamber is, for example, 0.5 x 10 ５ ~1.5 x 10 ５ The pressure is controlled to about Pa.

[0180] 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.

[0181] 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. The hydrogen atoms and radicals erode the surface of the metal substrate 23D, forming a fine concave-convex structure CS. While the plasma is being irradiated, the hydrogen atoms and radicals continue to erode the surface of the metal substrate 23D, and the recesses and protrusions of the concave-convex structure CS become larger. During this time, as hydrogen atoms enter the interior of the metal substrate 23D, tiny cavities VD are formed within the concave-convex structure CS.

[0182] 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.

[0183] The power 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 power 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.

[0184] 26a shows a photographed image I5 of active material layer 25D of first electrode 20D as an example, taken 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.

[0185]

[0186] FIG. 26b shows the Raman spectrum of the active material layer 25D of the captured 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 or amorphous carbon.

[0187] A lithium-ion battery coin cell was fabricated using the first electrode 20D shown in photographed image I5 under the conditions of Example E1 in Table 1 and Table 3 described in the first embodiment. During charging, this lithium-ion battery formed a layer of Li on the surface of the first electrode 20D due to the electrode reaction of chemical formula (2) described in the first embodiment. It was also confirmed that this lithium-ion battery exhibited improved battery performance compared to power storage devices that are charged by intercalation.

[0188] The power storage device 10D of the fifth embodiment shares the same electrode reaction for charging and discharging as the power storage device 10 of the first embodiment. Even in the power storage device 10D of the fifth embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the power storage device 10D of the fifth embodiment can achieve various effects similar to those described in the first embodiment.

[0189] 6. Sixth Embodiment FIG. 27 is a schematic diagram illustrating an electricity storage device 10E according to a sixth embodiment.

[0190] The power storage device 10E of the sixth embodiment has almost the same configuration as the power storage device 10 of the first embodiment, except for the configuration of the first electrode 20E. The first electrode 20E of the power storage device 10E of the sixth embodiment is formed of a metal substrate 23E that functions as a current collector.

[0191] No active material layer is provided on the metal substrate 23E. As shown in the balloon in Fig. 27 , the metal substrate 23E has a plurality of protrusions 46a formed of fine metal particles MP on its plate surface. When the power storage device 10E is charged, Li precipitates on the surfaces of the protrusions 46a.

[0192] In order to smoothly deposit Li during charging, the area of ​​the projection region of the protrusion 46a projected onto the surface of the metal substrate 23E must be 10 nm ２ 10000nm or more ２ The density of the protrusions 46a on the surface of the metal substrate 23E is preferably 1 / μm or less. ２ More than 1000 pieces / μm ２ Alternatively, it is preferable that the average value of the maximum length of the projected region of the convex portion 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 region is 1 / 10 or more of the area of ​​the surface of the metal substrate 23E.

[0193] The method for forming the protrusions 46a of the metal substrate 23E is also substantially the same as the method for forming 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 Japanese Patent Application Laid-Open No. 2022-187895.

[0194] 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 involved in charging and discharging is precipitated 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.

[0195] 28 illustrates a captured image I6 showing 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.

[0196] A lithium-ion battery coin cell was fabricated using the first electrode 20E shown in photographed image I6 under the conditions of Example E1 in Table 1 and Table 3 described in the first embodiment. During charging, the lithium-ion battery formed a layer of Li on the surface of the first electrode 20E due to the electrode reaction of chemical formula (2) described in the first embodiment. It was also confirmed that this lithium-ion battery exhibited improved battery performance compared to power storage devices that are charged by intercalation.

[0197] The electricity storage device 10E of the sixth embodiment shares the same electrode reaction for charging and discharging as the electricity storage device 10 of the first embodiment. Even in the electricity storage device 10E of the sixth embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the electricity storage device 10E of the sixth embodiment can achieve various effects similar to those described in the first embodiment.

[0198] 29a and 29b are schematic cross-sectional views each illustrating a cross-sectional structure of a first electrode 20F included in an electricity storage device 10F according to a seventh embodiment. Each of Figs. 29a and 29b illustrates a cross-sectional structure of the first electrode 20F taken along an arbitrary cross section along the thickness direction.

[0199] The seventh embodiment of the power storage device 10F has substantially the same configuration as the sixth embodiment of the power storage device 10E, except for the difference in the surface structure of the metal substrate 23F of the first electrode 20F. A fine uneven structure is formed on the outer surface of the metal substrate 23F of the seventh embodiment. 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.

[0200] The convex structure portion 52 is a portion that protrudes in the thickness direction of the metal substrate 23F. As will be described later, the convex structure portion 52 is 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.

[0201] The maximum width Wmax of the convex structure portion 52 corresponds to the maximum width of the convex structure portion 52 in any direction, as measured in an image of the metal substrate 23F taken in its thickness direction using, for example, a scanning electron microscope, etc. "All directions" refers to all directions perpendicular to the thickness direction of the metal substrate 23F.

[0202] 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. 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.

[0203] Figures 29a and 29b each show examples of the convex structure 52 having a different shape. Figure 29a shows a first convex body 52a as a first example of the convex structure 52. Figure 29b 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 described below in order.

[0204] 29a. The first convex body 52a, which is a first embodiment of the convex structure 52, is formed by a dense accumulation 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. 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.

[0205] 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, giving it a structure that protrudes from the surrounding area as a whole.

[0206] 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 a 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.

[0207] 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 with 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.

[0208] See Figure 29b. 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 height. The height of the convex bodies 52b and 52c corresponds 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.

[0209] The particle diameter Pq of the second convex bodies 52b is 0.5 μm or more and 5.0 μm or less, and the 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 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.

[0210] 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.

[0211] 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.

[0212] 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.

[0213] The area of ​​the projected region of the convex structure 52 including the convex bodies 52a, 52b, and 52c projected in the thickness direction of the metal substrate 23F is 0.01 μm ２ Larger than 10,000 μm ２Furthermore, 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 Above, 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.

[0214] A method for forming the convex structure portion 52 is disclosed in Japanese Patent Application Laid-Open No. 2024-016511. When the metal substrate 23F is made of Cu, an uneven structure including the convex structure portion 52 can be formed on the surface of the metal substrate 23F by performing electrolytic deposition under the following conditions. In the electrolytic deposition, for example, sulfuric acid (H O ) having a concentration of about 0.5 to 2.0 M (volume molar concentration mol / L) is used as an electrolyte. ２ SO ４ ) is used. Furthermore, an electrode plate made of crude copper is used as the anode, and the base material of the metal substrate 23F is used as the cathode, and a voltage of approximately 0.5 to 2.0 V is applied, and a current of approximately 80.0 to 200.0 mA is passed through it. As a result, the Cu on the electrode plate is oxidized and elutes as Cu ions into the electrolyte, which migrate toward the base material of the metal substrate 23F and are reduced and precipitated on the surface of the base material of the metal substrate 23F. The precipitated Cu particles form protruding structures 52 one after another on the base material surface.

[0215] 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 involved in charging and discharging is precipitated 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.

[0216] 30 shows photographed images I7a, I7b, I7c, and I7d illustrating examples of the convex structure portion 52 of the first electrode 20F according to the seventh embodiment. The photographed direction of the photographed images I7a and I7c is 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.

[0217] The photographed images I7a and I7b in the upper column of Fig. 30 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. 30 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 particles.

[0218] 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 produced by performing a surface treatment by electrolytic deposition on a Cu foil serving as the metal substrate 23F. In the electrolytic deposition for forming the second convex body 52b and the third convex body 52c, 1.5 M H ２ SO ４ A DC voltage of 1.0 V was applied to the Cu foil in the electrolyte solution, and a current of 128 mA was passed through the Cu foil. The distance between the substrate and the electrode was 3.5 cm.

[0219] A lithium-ion battery coin cell was fabricated using the first electrode 20F shown in photographed images I7a, I7b, I7c, and I7d under the conditions of Example E1 in Table 1 and Table 3 described in the first embodiment. During charging, the lithium-ion battery formed a Li layer on the surface of the first electrode 20F due to the electrode reaction of chemical formula (2) described in the first embodiment. It was also confirmed that this lithium-ion battery exhibited improved battery performance compared to power storage devices that are charged by intercalation.

[0220] The power storage device 10F of the seventh embodiment shares the same electrode reaction for charging and discharging as the power storage device 10 of the first embodiment. Even in the power storage device 10F of the seventh embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the power storage device 10F of the seventh embodiment can achieve various effects similar to those described in the first embodiment.

[0221] 8. Eighth Embodiment A metal substrate 23G of a first electrode 20G included in an electricity storage device 10G according to an eighth embodiment will be described with reference to FIGS. 31, 32, and 33. FIG.

[0222] 31 is a schematic diagram showing the configuration of an electricity storage device 10G according to an eighth embodiment. The electricity storage device 10G has substantially the same configuration as the electricity storage device 10E according to the sixth embodiment, except that it includes a metal substrate 23G having smooth surfaces and having been subjected to a heat treatment described below.

[0223] Through extensive research, the inventors of the present invention have found that if a metal substrate heat-treated under an 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 finding are disclosed in the specification of Japanese Patent Application No. 2024-023186.

[0224] The heat treatment of the metal substrate 23G is performed in an atmosphere gas at a predetermined temperature for a predetermined time. In this embodiment, a reducing gas is used as the atmosphere gas. For example, H ２ The reducing gas may be H ２ Instead of carbon monoxide (CO) or ammonia (NH ３ ), hydrocarbon gas, etc. may be used. Examples of hydrocarbon gases include methane (CH ４ ) and ethane (C ２ H ５ ), propane (C ３ H ８ ), butane (C ４ H １０ ), ethylene (C ２ H ４ ), acetylene (C ２ H ２ ) etc. may also be used.

[0225] The reducing gas is not limited to the above-mentioned examples, and 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 of these having dangling bonds.

[0226] As the atmospheric gas, an inert gas may be used instead of the reducing gas. Examples of the inert gas include argon (Ar), helium (He), xenon (Xe), and nitrogen (N ２ ) can be used.

[0227] 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 lower 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, the inert gas may be Ar or N ２ In this case, the oxygen partial pressure in the atmospheric gas is 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.

[0228] The treatment temperature in the heat treatment of this embodiment may be, for example, 400° C. or higher and 1000° C. or lower. The treatment temperature in the heat treatment is preferably 500° C. or higher, and more preferably 600° C. or higher. The treatment temperature in the heat treatment is further preferably 700° C. or higher, and more preferably 800° C. or higher.

[0229] 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.

[0230] The heat treatment time may be set to a time longer than the reduction time of the metal oxide, but from the viewpoint of suppressing an increase in manufacturing costs due to a longer process time, 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.

[0231] As will be described below, the metal substrate 23G that has been subjected to the above heat treatment has a two-dimensional diffraction image of the Debye rings obtained by a two-dimensional X-ray detector as a discontinuous arc-shaped image with an array of points or line segments.

[0232] Figures 32 and 33 show the changes in X-ray diffraction (XRD) of the metal substrate 23G when subjected to the heat treatment. Figure 32 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 Figure 32, the numbers in parentheses after Cu refer to Miller indices. Figure 33 shows two-dimensional diffraction images of the Debye rings obtained by a two-dimensional X-ray detector of the same Cu foil 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 Figures 32 and 33 are shown in Table 9 below.

[0233]

[0234] The X-ray diffraction pattern shown in Figure 32 shows that the number of prominent peaks was reduced after the heat treatment under the conditions of Table 5. For example, after the heat treatment, the Cu(220) peak was reduced to an almost negligible level. As a result, the I200 / I220 ratio, which is the ratio of the Cu(200) peak to the Cu(220) peak, increased from 1 before the heat treatment to 2000 after the heat treatment. Furthermore, the Cu(200) peak and the Cu(400) peak were significantly smaller after the heat treatment. This change in the X-ray diffraction pattern indicates that the metal particles constituting the metal substrate were coarsened by the heat treatment.

[0235] In the two-dimensional diffraction image before heat treatment shown in Figure 33, the Debye rings corresponding to the peaks shown in Figure 32 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 33 can be said to indicate the history of the metal substrate undergoing heat treatment.

[0236] 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 Example E1 in Table 1 and Table 3 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. It was also confirmed that this lithium-ion battery exhibited improved battery performance compared to power storage devices that are charged by intercalation.

[0237] The power storage device 10G of the eighth embodiment shares the same electrode reaction for charging and discharging as the power storage device 10 of the first embodiment. Even in the power storage device 10G of the eighth embodiment, the charge and discharge cycle characteristics can be dramatically improved by applying the same electrolyte solution 12 as described in the first embodiment. In addition, the power storage device 10G of the eighth embodiment can achieve various effects similar to those described in the first embodiment.

[0238] 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.

[0239] In each of the above embodiments, the lithium imide salt of the electrolyte solution is not limited to those described in the above embodiments. The lithium imide salt may be, for example, one of those described in the above embodiments, or one having a structure represented by the above-mentioned chemical formula (3), or a derivative thereof. For example, CTFSI-Li or a derivative thereof may be used as the lithium imide salt.

[0240] In each of the above embodiments, the organic solvent of the electrolyte solution is not limited to those described in the above embodiments. For example, the following organic solvents can be used. Furthermore, the organic solvent may be a derivative of any of the organic solvents exemplified in this specification, or a mixture thereof.

[0241] [Other examples of organic solvents] Ethylene carbonate (EC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), fluoroethylene carbonate (FEC), bis(2,2,2-trifluoroethyl)ether (BTFE), tris[(trifluoroethoxy)methane] (TFEO)

[0242] In each of the above-described embodiments, the power storage device may be configured as a power storage device other than a lithium ion battery, for example, a lithium ion capacitor.

[0243] In the above-described 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 the metal substrate, and a second configuration having an uneven structure on the plate surface of the metal substrate, and thus can be interpreted as being configured so that, during charging, a layer of metal atoms formed by the deposition of metal atoms is formed on the surface of the electrode.

[0244] 10. Example of embodiment: The present invention can be realized in the following embodiments.

[0245] [First Aspect] The first aspect is provided as an electric storage device. The electric storage device of the first aspect includes an electrolyte solution containing a lithium imide salt and an organic solvent, a container filled with the electrolyte solution, a positive electrode disposed in the electrolyte solution and having a compound containing lithium atoms that ionize in the electrolyte solution and participate in charge and discharge, a negative electrode disposed in the electrolyte solution and having a metal substrate forming a current collector, configured so that a layer of precipitated lithium atoms forms on the surface during charging, and an electrically insulating separator that divides the container into a first electrode chamber in which the negative electrode is disposed and a second electrode chamber in which the positive electrode is disposed, and that is permeable to lithium ions moving between the first electrode chamber and the second electrode chamber. The electric storage device of the first aspect includes electrodes configured to be charged by the formation of a layer of lithium atoms on the surface of the electrode. This electric storage device can significantly increase the charge capacity compared to conventional electric storage devices that charge by intercalation of lithium ions in the electrodes. Furthermore, this type of electricity storage device contains an electrolyte suitable for the electrodes, and therefore can dramatically improve the charge capacity and durability against repeated charge and discharge compared to conventional configurations.

[0246] [Second embodiment] In the power storage device of the first embodiment, the lithium imide salt is LiN(FSO ２ ) ２ , LiN(CF ３ SO ２ ) ２ , LiN(SO ２ C ２ F ５ ) ２ , derivatives thereof, and mixtures of any combinations thereof. According to the electricity storage device of the second embodiment, the electrolyte solution contains a suitable lithium imide salt, so that durability against repeated charge and discharge can be further improved.

[0247] [Third Aspect] In the electricity storage device according to the first or second aspect, the organic solvent may contain 1,2-dimethoxyethane (DME), 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), 1,2-diethoxyethane (DEE), triglyme (triglyme, triethylene glycol dimethyl ether 1,2-bis(methoxyethoxy)ethane 2,5,8,11-tetraoxadodecane), tetraglyme (dimethoxytetraethylene glycol tetraglyme), derivatives thereof, or a mixture of any combination thereof. According to the electricity storage device of the third aspect, the electrolyte solution contains a suitable lithium imide salt, thereby further improving durability against repeated charge and discharge.

[0248] [Fourth Aspect] In the electricity storage device according to any one of the first, second, and third aspects, the electrolyte solution further contains an additive, and the additive is vinylene carbonate (VC), lithium nitrate (LiNO ３ The fourth embodiment of the power storage device may include a boroxine compound including triisopropoxyboroxine (TiPBx), a derivative thereof, or a mixture of any combination thereof. According to the fourth embodiment of the power storage device, the battery performance can be further improved by adding an additive to the electrolyte solution.

[0249] [Fifth Aspect] In the power storage device according to any one of the first, second, third, and fourth aspects, the lithium imide salt is LiN(FSO ) having a concentration of 4 mol / L or more and 6 mol / L or less. ２ ) ２ The organic solvent may contain DME as a main component. According to the electricity storage device of the fifth aspect, it is possible to further improve durability against repeated charge and discharge.

[0250] [Sixth Aspect] In the electricity storage device according to the fifth aspect, the organic solvent may contain TTE together with DME. According to the electricity storage device of the sixth aspect, the charge / discharge efficiency of the electricity storage device can be further improved and further stabilized.

[0251] [Seventh Mode] In the electricity storage device according to any one of the first, second, third, fourth, fifth, and sixth modes, an active material layer of a carbon nanostructure mainly composed of graphene may be provided on a plate surface of the metal substrate. The electricity storage device of the seventh mode can further increase the charge capacity and durability against repeated charge and discharge.

[0252] [Eighth Mode] In the electricity storage device according to the seventh mode, the carbon nanostructures may be carbon nanowalls extending from the smooth surface of the metal substrate. In the electricity storage device of the eighth mode, the negative electrode active material layer is composed of carbon nanowalls, which can further increase the charge capacity and durability against repeated charge and discharge.

[0253] [Ninth Mode] In the electricity storage device according to the seventh mode, the surface of the active material layer may have a fine uneven structure in which a plurality of minute granules are densely arranged, and the carbon nanostructures, which extend thinly outward from the granules, may be arranged over the entire surface layer of the granules. According to the electricity storage device of the ninth mode, the active material layer of the negative electrode has an uneven structure constituted by the carbon nanostructures, which can further increase the charging capacity and can further increase durability against repeated charging and discharging.

[0254] [Tenth Mode] In the electricity storage device according to the seventh mode, the carbon nanostructure may have a base portion formed by stacking the graphene and extending elongatedly in a thickness direction of the metal substrate, and a plurality of extension portions formed of carbon and extending from the base. According to the electricity storage device of the tenth mode, the negative electrode active material layer is formed of a carbon nanostructure having a characteristic structure with a base portion and extension portions, thereby making it possible to further increase the charge capacity and durability against repeated charge and discharge.

[0255] [Eleventh embodiment] In the electricity storage device according to the seventh embodiment, the metal substrate may have a plurality of protrusions on the plate surface, and when viewed in the thickness direction of the metal substrate, 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 electricity storage device of the eleventh embodiment, the active material layer of the negative electrode has a characteristic structure in which linear carbon nanostructures are arranged on the protrusions on the metal substrate, thereby making it possible to further increase the charge capacity and durability against repeated charge and discharge.

[0256] [Twelfth Mode] In the electricity storage device according to any one of the first, second, third, fourth, fifth, and sixth modes, a fine uneven structure may be formed on the surface of the metal substrate, and the active material layer containing the carbon nanostructure composed of nanographene and amorphous carbon as a main component may be formed so as to densely cover the surface of the uneven structure. According to the electricity storage device of the twelfth mode, the negative electrode has a characteristic structure in which the active material layer composed of nanographene and amorphous carbon is formed so as to cover the uneven structure of the metal substrate, thereby further increasing the charge capacity and durability against repeated charge and discharge.

[0257] [13th Mode] In the electricity storage device according to any one of the first, second, third, fourth, fifth, and sixth modes, the metal substrate has a plate surface having a plurality of protrusions on the surface of which the lithium atoms are precipitated, and the area of ​​a projected region obtained by projecting the protrusions onto the plate surface of the metal substrate is 10 nm or less. ２ 10000nm or more ２ and the density of the protrusions on the plate surface is 1 / μm ２ More than 1000 pieces / μm ２ According to the electricity storage device of the thirteenth embodiment, by having protrusions on the surface of the metal substrate of the negative electrode, it is possible to further increase the charge capacity and further increase durability against repeated charge and discharge, even without providing an active material layer.

[0258] [14th Mode] In the electricity storage device according to any one of the first, second, third, fourth, fifth, and sixth modes, 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 regions 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 regions may be 1 / 10 or more of the area of ​​the plate surface. According to the electricity storage device of the 14th mode, by having the protrusions on the surface of the metal substrate of the negative electrode, it is possible to further increase the charge capacity and durability against repeated charge and discharge even without an active material layer.

[0259] [Fifteenth Mode] In the electricity storage device according to any one of the first, second, third, fourth, fifth, and sixth modes, the metal substrate may have a fine uneven structure on its plate surface, which is made of metal particles and has a maximum width of 0.5 μm to 30.0 μm, and which is made of a plurality of protrusions on whose surface the lithium atoms precipitate during charging. According to the electricity storage device of the fifteenth mode, by having the protrusions on the surface of the metal substrate of the negative electrode, it is possible to further increase the charge capacity and further increase durability against repeated charge and discharge, even without providing an active material layer.

[0260] [16th Mode] In the electricity storage device according to any one of the first, second, third, fourth, fifth, and sixth modes, a two-dimensional diffraction image of the Debye rings obtained by a two-dimensional X-ray detector on the metal substrate may be obtained as a discontinuous arc-shaped image in which points or line segments are arranged. According to the electricity storage device of the 16th mode, the negative electrode is formed of a metal substrate having a history of being subjected to a predetermined heat treatment, thereby further increasing the charge capacity and durability against repeated charge and discharge.

[0261] 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..., 20, 20A, 20B, 20C, 20D, 20E, 20F, 20G...first electrode (negative electrode), 21...current collector, 23, 23A, 23B, 23C, 23D, 23E, 23F, 23G...metal substrate, 25, 25A, 25B, 25C, 25D...active material layer, 30...second electrode (Positive electrode), 31...current collector, 35...active material layer, 40...granular body, 41...particle structure, 43...base, 44...extension, 46, 46a...protrusion, 48...surface protrusion, 52, 52a, 52b, 52c...protrusion, AC...amorphous carbon layer, VD...cavity, CN, CNb, CNc, CNd...carbon nanostructure, CS...uneven structure, CSs...surface uneven structure, GF...graphene, MP...metal particle, Pp...particle diameter, Pq...particle diameter, Pr...particle diameter, PR1...projection

Claims

1. An electricity storage device comprising: an electrolyte solution containing a lithium imide salt and an organic solvent; a container filled with the electrolyte solution; a positive electrode disposed in the electrolyte solution and having a compound containing lithium atoms that ionize in the electrolyte solution and participate in charging and discharging; a negative electrode disposed in the electrolyte solution and having a metal substrate that forms a current collector, and configured so that a layer of deposited lithium atoms is formed on the surface during charging; and an electrically insulating separator that divides the interior of the container into a first electrode chamber in which the negative electrode is disposed and a second electrode chamber in which the positive electrode is disposed, and that is permeable to lithium ions moving between the first electrode chamber and the second electrode chamber.

2. The power storage device according to claim 1, wherein the lithium imide salt is LiN(FSO ２ ) ２ , LiN(SO ２ CF ３ ) ２ , LiN(C ２ F ５ SO ２ ) ２ , their derivatives, and mixtures of any combination thereof.

3. The electricity storage device according to claim 2, wherein the organic solvent contains 1,2-dimethoxyethane (DME), 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether (TTE), 1,2-diethoxyethane (DEE), triglyme (triglyme, triethylene glycol dimethyl ether 1,2-bis(methoxyethoxy)ethane 2,5,8,11-tetraoxadodecane), tetraglyme (dimethoxytetraethylene glycol tetraglyme), derivatives thereof, or a mixture of any combination thereof.

4. The electricity storage device according to claim 3, wherein the electrolyte solution further contains an additive, and the additive is vinylene carbonate (VC), lithium nitrate (LiNO ３ ), boroxine compounds including triisopropoxyboroxine (TiPBx), derivatives thereof, and mixtures of any combinations thereof.

5. The power storage device according to claim 3, wherein the lithium imide salt is LiN(FSO) having a concentration of 4 mol / L or more and 6 mol / L or less. ２ ) ２ The electricity storage device, wherein the organic solvent contains DME as a main component.

6. The electricity storage device according to claim 4, wherein the organic solvent contains TTE together with DME.

7. An electricity storage device according to any one of claims 1 to 6, comprising an active material layer of a carbon nanostructure composed primarily of graphene on the surface of the metal substrate.

8. An electric storage device according to claim 7, wherein the carbon nanostructures are carbon nanowalls extending from the smooth surface of the metal substrate.

9. An electric storage device according to claim 7, wherein the surface of the active material layer has a fine uneven structure in which a plurality of minute particles are densely arranged, and the carbon nanostructures are arranged over the entire surface of the particles, extending in elongated shapes outward from the particles.

10. An energy storage device according to claim 7, wherein the carbon nanostructure has a base portion on which the graphene is stacked 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.

11. An energy storage device as described in claim 7, wherein the metal substrate has a plurality of protrusions 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 are distributed on the surface of the metal substrate.

12. An electricity storage device according to any one of claims 1 to 6, wherein a fine uneven structure is formed on the surface of the metal substrate, and an active material layer containing as its main component the carbon nanostructure made of the nanographene and amorphous carbon is formed so as to densely cover the surface of the uneven structure.

13. An electricity storage device according to any one of claims 1 to 6, wherein the metal substrate has a plurality of protrusions on the surface of which the lithium atoms are precipitated, and the area of ​​a projection region of the protrusions projected onto the surface of the metal substrate is 10 nm ２ 10000nm or more ２ the density of the protrusions on the plate surface is 1 / μm ２ More than 1000 pieces / μm ２ The following is an energy storage device.

14. An energy storage device according to any one of claims 1 to 6, wherein the metal substrate has a plurality of protrusions on the plate surface on which the lithium atoms precipitate, the average maximum length of the projection areas of the protrusions projected onto the plate surface is 10 nm or more and 200 nm or less, and the area occupied by the projection areas is 1 / 10 or more of the area of ​​the plate surface.

15. An energy storage device according to any one of claims 1 to 6, wherein the metal substrate has a fine uneven structure on the 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 protrusions on whose surface the lithium atoms precipitate during charging.

16. An electric storage device according to any one of claims 1 to 6, wherein a two-dimensional diffraction image of the Debye rings on 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.

Images