ELECTRODE FOR ELECTRIC STORAGE DEVICE, SECONDARY BATTERY, AND METHOD FOR MANUFACTURING ELECTRODE FOR ELECTRIC STORAGE DEVICE

Abstract

To provide a novel electrode for a power storage device that can enhance the performance of power storage device that use carbon as an active material.SOLUTION: An electrode for a power storage device has a metal substrate comprising a current collector, and an active material layer formed on the surface of the metal substrate and including carbon as an active material, the active material layer comprises a carbon nanostructure having a base on which graphene extending elongated in the thickness direction of the metal substrate is stacked, and a plurality of extensions comprising the carbon and extending out from the base.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present application relates to an electrode for an electricity storage device, a secondary battery, and a method for manufacturing an electrode for an electricity storage device. [Background technology]

[0002] Known examples of chargeable and dischargeable electricity storage devices include secondary batteries and electric double layer capacitors. In electrodes for these electricity storage devices, carbon may be used as an active material disposed on the surface of a current collector. For example, Patent Documents 1 and 2 below disclose a technique for forming an active material layer of a negative electrode of a lithium ion secondary battery from graphite or carbon nanowalls. When carbon nanowalls are applied to the active material layer, it is expected that the battery performance of the electricity storage device, such as the charging capacity and charging speed, will be improved compared to when graphite is applied. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2668678 [Patent Document 2] JP 2010-9980 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, the above-mentioned conventional active material layers have not yet been able to fully achieve the high battery performance required for electricity storage devices. The present application aims to provide an electrode for an electricity storage device having a novel active material layer that can improve the performance of the electricity storage device. [Means for solving the problem]

[0005] The inventors of the present invention, through their research into electrodes for electricity storage devices using carbon as an active material, have succeeded in developing an active material layer that has a structure different from that of conventional graphite or carbon nanowalls and can dramatically improve the performance of electricity storage devices. The present invention can be realized, for example, in the following forms.

[0006] The first embodiment of the present invention is provided as an electrode for an electricity storage device. The electrode for an electricity storage device of this embodiment includes a metal substrate constituting a current collector, and an active material layer formed on the surface of the metal substrate and containing carbon as an active material, the active material layer being composed of a carbon nanostructure having a base portion in which graphene is laminated and extending elongatedly in the thickness direction of the metal substrate, and a plurality of extension portions composed of the carbon and extending from the base portion. .

[0007] In this embodiment of the electrode for an electricity storage device, the active material layer is composed of a carbon nanostructure having a novel structure. When the active material layer is used, a dense, flat, and well-formed metal layer is formed on the surface of the electrode during charging of the electricity storage device, where metal ions involved in the charging reaction are precipitated. This improves the battery performance of the electricity storage device.

[0008] The present invention can be realized in various forms other than an electrode for an electricity storage device. For example, the present invention can be realized in the form of an electricity storage device such as a secondary battery including an electrode for an electricity storage device, a method for manufacturing an electrode for an electricity storage device, a method for manufacturing an electricity storage device, a method for manufacturing an active material layer, a manufacturing apparatus suitable for carrying out these manufacturing methods, a control program for controlling the manufacturing apparatus, a recording medium on which the control program is recorded, etc. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a schematic diagram showing the configuration of a secondary battery including an electrode for an electricity storage device. [Diagram 2] FIG. 2 is a schematic cross-sectional view showing a cross-sectional structure of an electrode. [Diagram 3]FIG. 1 is a schematic diagram showing the configuration of a carbon nanostructure. [Figure 4] FIG. 2 is a schematic diagram showing the deposition of metal atoms in an active material layer during charging. [Diagram 5] FIG. 2 is a process flow diagram showing a manufacturing process of a secondary battery. [Figure 6] FIG. 2 is a schematic diagram showing a configuration of a first processing apparatus. [Figure 7] FIG. 4 is a schematic diagram showing a configuration of a second processing apparatus. [Figure 8] Schematic diagram showing a process of generating an extension portion of a carbon nanostructure. [Figure 9] FIG. 4 is an explanatory diagram showing a photographed image in an embodiment. [Figure 10] 1A to 1C are explanatory diagrams showing, by photographic images, the growth process of a carbon nanostructure according to an embodiment of the present invention. [Figure 11] FIG. 11 is an explanatory diagram showing photographed images of an example and a comparative example. [Figure 12] FIG. 4 is an explanatory diagram showing the results of an evaluation test of the battery performance of the examples. [Figure 13] FIG. 4 is an explanatory diagram showing the results of an evaluation test of the battery performance of the first comparative example. [Figure 14] FIG. 11 is an explanatory diagram showing the results of an evaluation test of the battery performance of the second comparative example. [Figure 15] FIG. 4 is an explanatory diagram showing the results of evaluation tests of the battery performance of Examples and Comparative Examples. [Figure 16] FIG. 4 is an explanatory diagram showing photographed images of precipitated layers of metal atoms in an example and a comparative example. [Figure 17] FIG. 4 is an explanatory diagram showing photographed images of active material layers of an example and a comparative example on whose surfaces water droplets have been dropped. [Figure 18] FIG. 11 is an explanatory diagram showing a photographed image of an active material layer of a comparative example produced by a production method different from that of the example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, an embodiment of an electrode for an electricity storage device according to the present invention will be described with reference to the drawings. In this specification, the term "electricity storage device" refers to a chargeable and dischargeable electricity storage body, such as a secondary battery or an electric double layer capacitor, and an apparatus including the electricity storage body.

[0011] 1. Implementation: 1-1. Structure of secondary battery: Fig. 1 is a schematic diagram showing the configuration of a secondary battery 10 of this embodiment. The secondary battery 10 of this embodiment is a lithium ion secondary battery in which lithium ions are involved in charging and discharging. The secondary battery 10 includes a container 11, an electrolyte 12, a separator 15, a first electrode 20, and a second electrode 30. In Fig. 1, for convenience, the container 11 is shown by a dashed line, and the separator 15 is shown by a broken line.

[0012] The container 11 has an internal space filled with the electrolytic solution 12. The container 11 is liquid-tightly constructed from a material that is unlikely to react with the electrolytic solution 12. The electrolytic solution 12 has a property capable of transmitting metal ions involved in charging and discharging between the first electrode 20 and the second electrode 30. In this embodiment, the electrolytic solution 12 is constituted by a solution in which a lithium salt is dissolved in an organic solvent, and is capable of transmitting lithium ions between the first electrode 20 and the second electrode 30. For example, lithium hexafluorophosphate (LiPF6) can be used as the lithium salt of the electrolytic solution 12. For example, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. can be used as the organic solvent.

[0013] The separator 15 divides the internal space of the container 11 into a first electrode chamber 16 in which the first electrode 20 is accommodated and a second electrode chamber 17 in which the second electrode 30 is accommodated. The separator 15 has electrical insulation and ion conductivity, and electrically insulates the first electrode 20 from the second electrode 30 while allowing the lithium ions transmitted via the electrolyte 12 to pass through. The separator 15 is made of, for example, a resin film or nonwoven fabric having a porous structure.

[0014] The first electrode 20 corresponds to an electrode for a power storage device in this embodiment. In the secondary battery 10 of this embodiment, the first electrode 20 constitutes a negative electrode. The first electrode 20 includes a metal substrate 21 and an active material layer 22.

[0015] The metal substrate 21 constitutes a current collector. In this embodiment, the metal substrate 21 is made of a metal foil of copper (Cu). The metal substrate 21 may be made of a metal other than Cu. In other embodiments, the metal substrate 21 may be made of, for example, any one of a Cu alloy, aluminum (Al), and an Al alloy. The metal substrate 21 does not have to be made of a metal foil, and may be made of, for example, a thin metal plate. The metal substrate 21 does not have to be made of a flat plate, and may be bent into various shapes, such as a cylindrical shape or a corrugated shape.

[0016] The active material layer 22 is provided on both the first surface 21a and the second surface 21b of the metal substrate 21. The active material layer 22 contains carbon (C) as an active material. Details of the configurations of the metal substrate 21 and the active material layer 22 of the first electrode 20 and a manufacturing method will be described later. In the following description, the first electrode 20 will also be simply referred to as "electrode 20".

[0017] The second electrode 30 constitutes the positive electrode of the secondary battery 10. The second electrode 30 has a positive electrode current collector 31 and a positive electrode active material layer 32. The positive electrode current collector 31 is made of, for example, a metal foil such as Al or titanium (Ti). The positive electrode current collector 31 may be made of other metals and may have a form other than a metal foil. The positive electrode current collector 31 does not have to be configured in a flat shape, and may be bent into various shapes such as a cylindrical shape or a corrugated shape.

[0018] The positive electrode active material layer 32 is formed on each of the first surface 31a and the second surface 31b of the positive electrode current collector 31. The positive electrode active material layer 32 contains a positive electrode active material containing Li atoms, a conductive assistant, and a binder. The positive electrode active material layer 32 may contain a thickener. As the positive electrode active material, for example, a ternary substance can be used, and lithium cobalt oxide (LiCoO2), lithium manganese oxide (LMO), or lithium nickel oxide (NCA) can be used. As the conductive assistant, for example, acetylene black or carbon black can be used. As the binder, for example, polyvinylidene fluoride (PVDF) or styrene butadiene rubber (SBR) can be used. As the thickener, for example, carboxymethyl cellulose (CMC) can be used.

[0019] The configuration of the electrode 20 of this embodiment will be described with reference to FIG. 2 and FIG.

[0020] Fig. 2 is a schematic cross-sectional view showing a cross-sectional structure of the electrode 20 taken along an arbitrary cut surface in the thickness direction. Fig. 2 shows the configuration of the electrode 20 on the first surface 21a side of the metal substrate 21. The configuration of the electrode 20 on the second surface 21b side of the metal substrate 21 is the same as the configuration on the first surface 21a side shown in Fig. 2.

[0021] As described above, the active material layer 22 is provided on the surface of the metal substrate 21. The active material layer 22 has an amorphous carbon layer 23 covering the surface of the metal substrate 21, and a carbon nanostructure 25 formed on the amorphous carbon layer 23.

[0022] The amorphous carbon layer 23 is a thin film layer made of carbon, and is the starting point for the growth of the carbon nanostructures 25. The amorphous carbon layer 23 is well formed, thereby improving the state of formation of the carbon nanostructures 25. The thickness of the amorphous carbon layer 23 is preferably, for example, 10 nm or more and 300 nm or less. The thickness of the amorphous carbon layer 23 is more preferably 10 nm or more and 100 nm or less, and further preferably 12 nm or more and 30 nm or less.

[0023] The carbon nanostructures 25 are minute structures made entirely of carbon, and are formed so as to be distributed over the entire surface of the amorphous carbon layer 23. The carbon nanostructures 25 have a base 26 that extends elongatedly in the thickness direction of the metal substrate 21, and a plurality of extensions 27 that extend from the base 26. Many of the extensions 27 are formed so as to branch out in a branch-like manner on the upper end side of the base 26. The carbon nanostructures 25 are graphite-like substances, and therefore have a higher electrical conductivity than carbon materials such as activated carbon.

[0024] Fig. 3 is a schematic diagram showing the configuration of a single carbon nanostructure 25. For convenience, graphene GS constituting base 26 is shown in Fig. 3 as a substantially rectangular sheet. Also, for convenience, a plurality of extensions 27 are shown by dashed lines in Fig. 3.

[0025] The base 26 has a multilayer structure in which a plurality of graphene GS are stacked in the thickness direction. Graphene GS, also called a graphene sheet, is a sheet-like material having a thickness of one carbon atom and composed of a six-membered carbon ring structure, that is, a hexagonal lattice structure with carbon atoms as vertices.

[0026] The number of layers of graphene GS in the base 26 varies, and the base 26 is formed in a needle-like, plate-like, or pleated shape. The base 26 can also be interpreted as a structure similar to a carbon nanowall or the like such as a carbon nanoflake or a carbon nanoflower. The base 26 is arranged in a random mesh on the surface of the metal substrate 21, as shown in the photographed image later.

[0027] The base 26 does not have to be entirely made of single crystals of carbon six-membered rings. The graphene GS constituting the base 26 may not have a complete graphene structure, but may be a thin film mainly composed of carbon having a six-membered ring structure. The graphene GS may have a mosaic structure mainly composed of carbon having a six-membered ring structure. The mosaic structure means a structure in which a plurality of regions composed of carbon six-membered ring structures are discretely arranged.

[0028] The height Ha of the base 26 corresponds to the length from the lower end of the base 26 on the metal substrate 21 side to the apex, that is, the height from the surface of the amorphous carbon layer 23 to the upper end of the graphene GS. The average height Ha of the base 26 is preferably 0.1 μm or more, and more preferably 0.5 μm or more. The average height Ha of the base 26 is further preferably 0.8 μm or more. The average height Ha of the base 26 may be 50.0 μm or less. The average height Ha of the base 26 is preferably 25.0 μm or less, and more preferably 10.0 μm or less. The average height Ha of the base 26 is further preferably 5.0 μm or less. The average height Ha of the base 26 is further preferably 2.5 μm or less, and even more preferably 2.0 μm or less.

[0029] The average thickness W of the base 26 is, for example, preferably 0.5 nm or more and 100.0 nm or less, more preferably 1.0 nm or more and 50.0 nm or less, and even more preferably 1.5 nm or more and 30.0 nm or less.

[0030] Each extension 27 is made of carbon and is formed in a needle, column, plate, or pleat shape. Most of the extensions 27 are randomly distributed on the surface of the upper end of the base 26. By forming each extension 27 on the base 26, the gaps between the carbon nanostructures 25 near the surface of the active material layer 22 are reduced.

[0031] The height Hb of the carbon nanostructure 25 corresponds to the height from the lower end of the base 26 on the metal substrate 21 side to the upper end of the extension 27. The height Hb of the carbon nanostructure 25 is preferably 0.5 μm or more, and more preferably 0.8 μm or more. Moreover, the height Hb of the carbon nanostructure 25 is further preferably 1.0 μm or more, and even more preferably 1.2 μm or more.

[0032] However, the taller the carbon nanostructure 25 is formed, the longer the time required to form the carbon nanostructure 25. Therefore, from the viewpoint of increasing the productivity of the electrode 20, it is preferable that the average height Hb of the carbon nanostructures 25 is 10.0 μm or less. It is more preferable that the average height Hb of the carbon nanostructures 25 is 8.0 μm or less, and even more preferable that the average height Hb of the carbon nanostructures 25 is 5.0 μm or less. It is even more preferable that the average height Hb of the carbon nanostructures 25 is 3.0 μm or less.

[0033] Here, the higher the density of the carbon nanostructures 25 in the active material layer 22, the higher the battery performance of the secondary battery 10 can be. In this specification, the density of the carbon nanostructures 25 in the active material layer 22 is a value obtained as follows. Each carbon nanostructure 25 is divided into a plurality of unitary units for each predetermined volume. In an image taken facing the surface of the active material layer 22, the number of unitary units present per unit area is measured as the density.

[0034] In the active material layer 22, the density of the carbon nanostructure 25 is 1 μm 2 It is preferable that the number of particles is 50 or more per 1 μm. 2 It is more preferable that the density of the carbon nanostructures 25 is 60 or more per unit area. It is further preferable that the density of the carbon nanostructures 25 is 70 or more per unit area.

[0035] However, if the density of the carbon nanostructures 25 in the active material layer 22 is excessively increased, it takes time and effort to form the carbon nanostructures 25, which may reduce the productivity of the electrode 20. 2 Preferably, there are 200 or less per unit area, and more preferably, there are 100 or less per unit area.

[0036] The density of carbon nanostructures 25 in active material layer 22 increases as the average spacing between adjacent carbon nanostructures 25 in active material layer 22 decreases, and decreases as the average spacing increases. The average spacing here is a value calculated by drawing straight lines in a fixed direction at a plurality of predetermined locations on a captured image in which carbon nanostructures 25 are projected in the height direction, and averaging the measured values ​​of the lengths of line segments partitioned by adjacent carbon nanostructures 25 on each straight line.

[0037] The average spacing between the carbon nanostructures 25 in the active material layer 22 is preferably 40 nm or less, more preferably 30 nm or less, and even more preferably 20 nm or less. However, the average spacing is preferably 10 nm or more.

[0038] 1-2. Battery reaction in secondary batteries: The chemical reactions occurring during charging and discharging in the secondary battery 10 can be expressed, for example, by the following reaction formula. When the positive electrode material is LiCoO2, the reaction formula at the second electrode 30, which is the positive electrode, is expressed by the following formula (1). x represents the proportion of reacting atoms and is a real number greater than 0 and less than 1. Li 1-x CoO2+ xLi + + xe- ⇔ LiCoO2…(1)

[0039] In contrast, the reaction formula at the negative electrode 20 is expressed by the following formula (2): As shown in formula (2), lithium is deposited on the surface layer of the electrode 20 when the secondary battery 10 is charged. Li + + e- ⇔ Li …(2)

[0040] Here, in the case of a conventional negative electrode structure in which graphite is arranged as an active material on the surface of a flat metal substrate, in principle, one lithium ion is absorbed for every six carbon atoms during charging, forming lithium carbide (LiC6). Therefore, the reaction formula for the conventional structure as a comparative example is expressed as the following formula (3). Reaction formula in conventional configuration: xLi + +C6+xe - ⇔ Li x C6…(3)

[0041] As shown in the above formula (3), in the case of a conventional electrode that uses graphite as the negative electrode active material, the number of lithium ions that can be absorbed by charging is determined by the number of carbon atoms contained in the active material layer.

[0042] In contrast, in the case of the electrode 20 used in the secondary battery 10 of this embodiment, as shown in the above formula (2), theoretically, charging is possible as long as lithium can be precipitated without being limited by the number of carbon atoms in the active material layer 22. In other words, according to the electrode 20 of this embodiment, two or more lithium ions per carbon atom can be involved in a charge / discharge reaction in one charge or discharge. Therefore, the secondary battery 10 of this embodiment has an increased charge capacity by including the electrode 20 as the negative electrode.

[0043] Furthermore, in the secondary battery 10 of this embodiment, the carbon nanostructures 25 of the active material layer 22 of the electrode 20 have the extensions 27, thereby improving the battery performance compared to a case in which the carbon nanostructures 25 do not have the extensions 27. The inventor of the present invention surmises the reason for this as follows.

[0044] 4(a) is a schematic diagram showing how metal atoms 28 are precipitated in active material layer 22 of electrode 20 upon charging in secondary battery 10 of this embodiment. As described above, metal atoms 28 are lithium atoms.

[0045] 4(b) is a schematic diagram showing a state in which metal atoms 28 are precipitated in the active material layer 22a of the electrode 20a in the secondary battery 10a of the comparative example due to charging. The secondary battery 10a of the comparative example has almost the same configuration as the secondary battery 10 of the present embodiment, except that the active material layer 22a of the electrode 20a does not have the extension portion 27 and is composed of the carbon nanostructure 25a composed only of the portion corresponding to the base portion 26.

[0046] According to the nucleation theory, in the active material layer 22 of the secondary battery 10 of this embodiment, the multiple extensions 27 of the carbon nanostructure 25 can function as protrusions that serve as starting points for promoting the precipitation of metal atoms 28. Therefore, according to the active material layer 22 of this embodiment having a large number of minute protrusions, the metal atoms 28 are efficiently precipitated during charging.

[0047] 4(b), the carbon nanostructure 25a constituting the active material layer 22a of the secondary battery 10a of the comparative example has many flat surfaces, and the efficiency of precipitating the metal atoms 28 is lower than that of the carbon nanostructure 25 of this embodiment. Therefore, according to the secondary battery 10 of this embodiment, it is possible to precipitate the metal atoms 28 more efficiently and in a shorter time during charging than the secondary battery 10a of the comparative example.

[0048] Furthermore, in the active material layer 22 of the secondary battery 10 of this embodiment, the presence of the multiple extensions 27 reduces the gaps present between the carbon nanostructures 25. Therefore, when the secondary battery 10 is charged, the formation of a layer of metal atoms 28 having a denser and smoother surface is promoted, the thickness of the layer of metal atoms 28 increases, and the amount of deposition of metal atoms 28 can be increased.

[0049] In contrast, in the active material layer 22a of the secondary battery 10a of the comparative example, the gaps between the carbon nanostructures 25a are increased by the amount corresponding to the absence of the extensions 27. Therefore, the metal atoms 28 are not sufficiently precipitated between the carbon nanostructures 25a, and there is a possibility that voids VS are generated inside the layer of the metal atoms 28.

[0050] In this way, the secondary battery 10 of this embodiment can increase the amount of metal atoms 28 precipitated on the electrode 20 compared to the secondary battery 10a of the comparative example when charged under the same charging conditions. Therefore, the secondary battery 10 of this embodiment can increase the charging capacity compared to the secondary battery 10a of the comparative example.

[0051] Furthermore, according to the secondary battery 10 of this embodiment, as described above, the precipitation of the metal atoms 28 in the electrode 20 is promoted, so that the layer of the metal atoms 28 is easily formed uniformly, enabling stable and smooth charge and discharge reactions. In addition, according to the secondary battery 10 of this embodiment, the layer of the metal atoms 28 is formed more evenly, so that the amount of precipitation of the metal atoms 28 is prevented from increasing locally, and thus the generation of dendrites can be suppressed.

[0052] 1-3. Manufacturing method of secondary battery: 5 is a process flow diagram showing the manufacturing process of the secondary battery 10. Processes P1 and P2 are processes for manufacturing the electrode 20. In processes P1 and P2, carbon nanostructures 25 constituting the active material layer 22 of the electrode 20 are formed by two types of CVD (chemical vapor deposition) methods. The two types of CVD methods in this embodiment are a radical-injection plasma-enhanced (RI-PE) CVD method and a capacitively coupled plasma (CPP) CVD method.

[0053] Step P1 corresponds to a step of growing bases 26 of carbon nanostructures 25 on the surface of a metal substrate 21 by using an RI-PECVD apparatus.

[0054] 6 is a schematic diagram showing the configuration of a first processing apparatus 40, which is an RI-PECVD apparatus used in step P1. The first processing apparatus 40 includes, at its upper stage, a plasma generation chamber 41, a waveguide 42, a quartz window 43, a slot antenna 44, a microwave generator 45, and a radical source supply unit 46.

[0055] The plasma generation chamber 41 is a space where surface wave plasma (SWP) is generated by microwaves. The waveguide 42 is a space for transmitting microwaves to the plasma generation chamber 41. The waveguide 42 is partitioned by a quartz window 43 at the upper stage of the plasma generation chamber 41. A slot antenna 44 is arranged on the quartz window 43.

[0056] The microwave generating unit 45 introduces microwaves MW into the waveguide 42. The microwave generating unit 45 can generate microwaves with a frequency of 2.00 to 3.00 GHz, for example, with a power of 300 to 500 W. The microwaves MW introduced into the waveguide 42 are introduced into the plasma generation chamber 41 by the slot antenna 44.

[0057] When microwaves MW are introduced into the plasma generation chamber 41, high density plasma (HDP) is generated at the quartz window 43. The high density plasma HDP diffuses into the plasma generation chamber 41 and becomes a surface wave plasma SWP.

[0058] The radical source supply unit 46 supplies gas serving as a radical source to the plasma generation chamber 41. For example, hydrogen can be used as the radical source. The gas serving as the radical source is not limited to hydrogen, and may be, for example, oxygen, nitrogen, or other gases. Ions of the gas serving as the radical source are mixed into the surface wave plasma SWP of the plasma generation chamber 41.

[0059] The first processing apparatus 40 further includes, below the plasma generation chamber 41, a reaction chamber 50, a partition wall 51, a raw material gas supply unit 54, a power supply unit 55, a support base 56, a heater 57, and an exhaust unit 58.

[0060] The reaction chamber 50 is partitioned below the plasma generation chamber 41 by a metal partition wall 51. The partition wall 51 is provided with a plurality of through holes 52 for allowing the surface wave plasma SWP generated in the plasma generation chamber 41 to flow into the reaction chamber 50.

[0061] As described above, ions of the radical source are mixed into the surface wave plasma SWP in the plasma generation chamber 41. Most of the ions of the radical source collide with the partition wall 51 provided between the reaction chamber 50 and the reaction chamber 50, and are neutralized to become radicals, which are then introduced into the reaction chamber 50 together with the surface wave plasma SWP.

[0062] A gas flow passage 53 for supplying a raw material gas to the reaction chamber 50 is provided inside the partition wall 51. A raw material gas supply unit 54 is connected to the gas flow passage 53, and supplies a raw material gas into the reaction chamber 50 through the gas flow passage 53.

[0063] The raw material gas contains a carbon-based gas containing carbon that constitutes the carbon nanostructure 25, and a reaction contributing gas that contributes to the growth of the carbon nanostructure 25. Although detailed illustration is omitted in Fig. 6 for convenience, the raw material gas supply unit 54 has a similar configuration to the raw material gas supply unit 65 of the second processing device 60 shown in Fig. 7, and is capable of adjusting the flow rates of the carbon-based gas and the reaction contributing gas.

[0064] As the carbon-based gas, for example, methane (CH4) or hexafluoroethane (C2F6) can be used. As the reaction contributing gas, for example, hydrogen (H2) or argon (Ar) can be used. The reaction contributing gas promotes the conversion of the carbon-based gas to plasma by the Penning effect in the plasma processing. In addition, the reaction contributing gas is ionized in the plasma processing and collides with the metal substrate 21 to be processed, thereby forming nuclei that become the growth starting points of the carbon nanostructures 25.

[0065] The power supply unit 55 is connected to the partition wall 51 and applies a high-frequency voltage for plasma processing to the partition wall 51. The power supply unit 55 is capable of applying a high-frequency voltage with a power of 300 to 400 W and a frequency of 80 to 120 MHz. The partition wall 51 functions as an electrode for plasma processing.

[0066] The support base 56 is provided below the partition wall 51 and has a mounting surface 56s facing the partition wall 51. The metal substrate 21 is placed on the mounting surface 56s. The support base 56 is earthed and functions as an electrode for plasma processing. The heater 57 is provided inside the support base 56 and heats the metal substrate 21 placed on the mounting surface 56s of the support base 56 to a predetermined temperature.

[0067] The exhaust unit 58 is connected to the reaction chamber 50. The exhaust unit 58 includes a vacuum pump, and the vacuum pump controls the inside of the reaction chamber 50 to a predetermined pressure during plasma processing. In addition to the above-mentioned components, the first processing apparatus 40 may include a measuring unit equivalent to the vacuum gauge 81 and thermocouple 82 of the second processing apparatus 60 shown in FIG. 7.

[0068] In step P1, first, the metal substrate 21 is placed in the reaction chamber 50 of the first processing apparatus 40. The metal substrate 21 is placed on the mounting surface 56s of the support base 56. The heater 57 heats the metal substrate 21 to a temperature of, for example, about 600 to 800°C.

[0069] In step P1, the microwave generation unit 45 generates microwaves having a frequency of 2.00 to 3.00 GHz, for example, with a power of 300 to 500 W. The microwaves are introduced into the plasma generation chamber 41 through the waveguide 42 and the slot antenna 44. A radical source gas is also supplied to the plasma generation chamber 41 from the radical source supply unit 46. As a result, a surface wave plasma SWP containing radicals is generated in the plasma generation chamber 41 as described above, and is introduced into the reaction chamber 50 through the through-hole 52 of the partition wall 51.

[0070] Furthermore, in step P1, the raw material gas supply unit 54 supplies raw material gas to the reaction chamber 50. The raw material gas supply unit 54 supplies, as the raw material gas, for example, a carbon-based gas at a flow rate of 80 to 120 sccm, and also supplies a reaction contributing gas at a flow rate of 40 to 60 sccm. The pressure inside the reaction chamber 50 is controlled by the exhaust unit 58 to, for example, about 0.5 to 1.5 Pa.

[0071] While the source gas is being supplied to the reaction chamber 50, the power supply unit 55 applies a high-frequency voltage to the partition wall 51. The power supply unit 55 applies a high-frequency voltage with a frequency of 80 to 120 MHz, for example, at a power of 300 to 500 W. The plasma processing in the first processing device 40 continues for, for example, about 5 to 15 minutes.

[0072] In the plasma treatment, a capacitively coupled plasma CCP is generated between the partition 51 and the metal substrate 21 on the support base 56. When the capacitively coupled plasma CCP is generated, first, an amorphous carbon layer 23 is formed so as to cover the entire surface of the metal substrate 21. Then, bases 26 of the carbon nanostructures 25 are generated so as to be distributed over the entire surface of the metal substrate 21. Each base 26 grows so as to extend upward from the amorphous carbon layer 23.

[0073] Returning to Fig. 5, step P2 corresponds to a step of forming a plurality of extension portions 27 on the base portion 26 generated in step P1 by using a CCP-CVD apparatus.

[0074] 7 is a schematic diagram showing the configuration of second processing apparatus 60, which is a CCP-CVD apparatus used in process P2. Second processing apparatus 60 includes a reaction chamber 61, an exhaust unit 62, a source gas supply unit 65, a support base 70, an upper electrode 75, and a power supply unit 76. Second processing apparatus 60 further includes a vacuum gauge 81 and a thermocouple 82 as measuring units.

[0075] The reaction chamber 61 has an airtight structure capable of maintaining a vacuum. The reaction chamber 61 is connected to an exhaust unit 62 and a raw material gas supply unit 65. The exhaust unit 62 is equipped with a vacuum pump, and controls the reaction chamber 61 to a predetermined pressure (degree of vacuum) during plasma processing. The degree of vacuum in the reaction chamber 61 is measured by a vacuum gauge 81.

[0076] The source gas supply unit 65 supplies the source gas to the reaction chamber 61. The source gas supply unit 65 includes a storage unit 66, a flow rate control unit 67, and an introduction pipe 68. The storage unit 66 stores a plurality of types of gases constituting the source gas, sorted by type. The source gas used in the second processing device 60 is the same as that described in the second processing device 60.

[0077] In the storage unit 66, the multiple types of gases are stored in tanks (not shown) individually. The flow rate control unit 67 includes a gas delivery device 67a and a flow rate adjustment valve 67b. The gas delivery device 67a and the flow rate adjustment valve 67b are provided in the pipes for the multiple types of gases connected to the storage unit 66, respectively. The gas delivery device 67a is composed of, for example, an ejector or a pump, and delivers the gas from the storage unit 66 at a predetermined pressure. The flow rate of the gas delivered by the gas delivery device 67a is controlled by the flow rate adjustment valve 67b. The various gases whose flow rates are adjusted by the flow rate adjustment valve 67b join together in the introduction pipe 68. The introduction pipe 68 delivers the raw material gas, in which the multiple types of gases are mixed at a predetermined ratio, into the reaction chamber 61.

[0078] A support base 70 is provided in the reaction chamber 61. The support base 70 includes a susceptor 71, a quartz cover 72, and a heater 73. The susceptor 71 constitutes a surface on which the metal substrate 21 is placed. The metal substrate 21 is placed on the susceptor 71. The susceptor 71 is earthed. The susceptor 71 may be floating.

[0079] The susceptor 71 is disposed on a quartz cover 72, and a heater 73 is provided below the quartz cover 72. The quartz cover 72 protects the heater 73. In addition, the quartz cover 72 supports the susceptor 71 and prevents the heater 73 from directly contacting the susceptor 71.

[0080] During the plasma processing, the metal substrate 21 is heated by receiving radiant heat from the heater 73 via the susceptor 71. The thermocouple 82 measures the heating temperature of the heater 73. During the plasma processing, the heating of the metal substrate 21 by the heater 73 is controlled based on the temperature measured by the thermocouple 82.

[0081] An upper electrode 75 is provided at the top of the reaction chamber 61. The upper electrode 75 is provided on the susceptor 71 so as to face the metal substrate 21 to be processed. The upper electrode 75 is preferably provided so as to be approximately parallel to the metal substrate 21. The distance between the upper electrode 75 and the susceptor 71 is, for example, about 1 to 5 cm. The upper electrode 75 is connected to a power supply unit 76 provided outside the reaction chamber 61.

[0082] The power supply unit 76 is a high-frequency power supply device. The power supply unit 76 can apply a high-frequency voltage with a power of, for example, 2000 to 3000 W and a frequency of 12 to 15 MHz to the upper electrode 75. When the raw material gas is supplied to the reaction chamber 61 by the storage unit 66, the power supply unit 76 applies a high-frequency voltage to the upper electrode 75 to generate a high-density capacitively coupled plasma in the reaction chamber 61.

[0083] In step P2, first, the metal substrate 21 on which the bases 26 of the carbon nanostructures 25 have been generated in step P1 is placed on the support base 70 in the reaction chamber 61. The heater 73 heats the metal substrate 21 to a temperature of, for example, 600 to 800°C.

[0084] In step P2, the raw material gas supply unit 65 supplies raw material gas to the reaction chamber 50. The raw material gas supply unit 65 supplies, as the raw material gas, for example, a carbon-based gas at a flow rate of 80 to 120 sccm, and also supplies a reaction contributing gas at a flow rate of 40 to 60 sccm. The exhaust unit 62 controls the pressure inside the reaction chamber 50 to, for example, 5 to 15 Pa.

[0085] While the source gas is being supplied to the reaction chamber 61, the power supply unit 76 applies a high frequency voltage to the upper electrode 75. The power supply unit 76 applies a high frequency voltage with a frequency of 12 to 15 MHz, for example, at a power of 2000 to 3000 W. The power supply unit 76 gradually increases the power to the target power in about several tens of seconds to several minutes.

[0086] The plasma treatment in the second processing apparatus 60 continues for, for example, about 5 to 15 minutes. By the plasma treatment in the second processing apparatus 60, a plurality of extensions 27 are formed on the surface of each of the bases 26 formed on the metal substrate 21 in the process P1.

[0087] Fig. 8 is a schematic diagram showing a process of forming a plurality of extension portions 27 by plasma treatment in step P2. Fig. 8 shows a schematic view of the state of metal substrate 21 at elapsed times t1, t2, t3, and t4 during the plasma treatment in step P2.

[0088] At time t1, when the plasma treatment of step P2 is started, as described above, the base 26 extending from the amorphous carbon layer 23 is formed on the metal substrate 21. At time t2, intermediate carbon nanostructures CM made of carbon are formed on the surface of the base 26. Most of the intermediate carbon nanostructures CM are formed on the upper end side of the base 26. At times t3 to t4, protrusions PM gradually extend from the intermediate carbon nanostructures CM to become extensions 27. In this manner, the carbon nanostructures 25 of this embodiment are formed on the metal substrate 21.

[0089] Returning to Fig. 5, in step P3, the second electrode 30 that will become the positive electrode is manufactured. In step P4, as shown in Fig. 1, the first electrode 20 and the second electrode 30 are assembled into a container 11 filled with an electrolytic solution 12. Through the above steps, the secondary battery 10 is completed.

[0090] According to the above process, it is possible to form a carbon nanostructure 25 having a plurality of extensions 27 formed on a base 26, and to obtain a secondary battery 10 including the carbon nanostructure 25 as the active material layer 22 of an electrode 20. As described above, if the carbon nanostructure 25 is used as the active material layer 22 of a secondary battery 10, the charging capacity and charging speed can be increased, and the battery performance is improved. EXAMPLES

[0091] Fig. 9 is an explanatory diagram showing photographed images of the above-mentioned active material layer 22 in Example E1. Fig. 9(a1) and (b1) show photographed images showing the base 26 of the carbon nanostructure 25 formed by step P1. Fig. 9(a2) and (b2) show photographed images showing the carbon nanostructure 25 with the extension 27 formed by step P2. The photographed images of Fig. 9(a1) and (a2) were each taken by a scanning electron microscope in the thickness direction of the metal substrate 21, and the photographed images of Fig. 9(a1) and (a2) were each taken by a scanning electron microscope in a direction perpendicular to the thickness direction of the metal substrate 21.

[0092] In Example E1, copper foil was used as the metal substrate 21. Example E1 was produced by carrying out the plasma treatments of steps P1 and P2 under the conditions shown in the following Table 1. In step P2, the power of the power supply unit 76 was gradually increased from 0 W to 2000 W in about 1 minute.

[0093] [Table 1]

[0094] As shown in the photographed image of Fig. 9(b1), the average value of the height Ha of the base 26 formed in step P1 was about 1.0 µm. Also, as shown in the photographed image of Fig. 9(b2), the average value of the height Hb of the carbon nanostructure 25 in which the extension 27 was formed in step P2 was about 1.3 µm. In this way, the height of the carbon nanostructure 25 was about 30% higher than the base 26 by the amount of the extension 27 formed.

[0095] The average distance between the bases 26 formed in step P1 is about 73 nm, and the density of the bases 26 is about 1 μm 2 By forming the extensions 27 in step P2, the average spacing between the carbon nanostructures 25 was about 20 nm, and the density of the carbon nanostructures 25 was about 1 μm 2 The average spacing between the carbon nanostructures 25 was reduced by about 30% compared to the average spacing between the bases 26, and the density of the carbon nanostructures 25 was increased by about 50% compared to the density of the bases 26.

[0096] In Example E1, the amorphous carbon layer 23 was formed below the carbon nanostructure 25. The film thickness of the amorphous carbon layer 23 was generally within the range of 10 nm or more and 300 nm or less.

[0097] Fig. 10 is a set of images showing the growth process of extension portion 27 in step P2. The images in Fig. 10 were taken of a number of samples S1 to S4 in which the processing time of step P2 was varied. The upper image was taken by a scanning electron microscope in the thickness direction of metal substrate 21, and the lower image was taken by a scanning electron microscope in a direction perpendicular to the thickness direction of metal substrate 21. The processing conditions for steps P1 and P2 were the same as those of Example E1 described above.

[0098] Sample S1 corresponds to the sample in which only the base 26 is formed before the execution of step P2. Sample S2 shows the state one minute after the start of the execution of step P2. In the photographed image of sample S2, it was confirmed that the intermediate carbon nanostructure CM described in FIG. 8 had begun to be formed on the surface of the base 26.

[0099] Sample S3 shows the state 5 minutes after the start of execution of step P2. In the image of sample S3, it was confirmed that the protrusions PM described in FIG. 8 were beginning to form from the intermediate carbon nanostructures CM. Sample S4 shows the state 10 minutes after the start of execution of step P2. In the image of sample S4, it was confirmed that the protrusions PM had grown to become extensions 27.

[0100] 11 to 15, the evaluation results of the battery performance of secondary batteries using the electrodes of Example E1 and Comparative Examples C1 and C2 will be described.

[0101] Fig. 11 is an explanatory diagram showing photographed images of the active material layers of Example E1 and Comparative Examples C1 and C2. The photographed images in Fig. 11 were taken by a scanning electron microscope facing directly onto the surfaces of the active material layers.

[0102] Example E1 is the same as that described in FIG. 9. In Comparative Examples C1 and C2, the same copper foil as in Example E1 was used as the metal substrate. Comparative Example C1 was produced under the same conditions as Example E1, except that step P2 for forming the extension portion 27 was not performed. The active material layer of Comparative Example C1 was composed of carbon nanowalls. In Comparative Example C2, an active material layer of uniform thickness was provided using graphite.

[0103] 12 to 14 show graphs obtained by charging and discharging the secondary battery using the electrodes of Example E1 and Comparative Examples C1 and C2 as the negative electrodes. In Figs. 12 to 14, the relationship between the voltage and the charge capacity of the secondary battery is shown by a solid line graph during charging and by a dashed line graph during discharging. In Fig. 15, the charge capacity and specific capacity of the secondary battery using Example E1 and Comparative Examples C1 and C2 are shown by bar graphs. In this evaluation test, the charge current and discharge current were both set to 0.5 mA.

[0104] The secondary batteries used in Example E1 and Comparative Examples C1 and C2 were lithium ion secondary batteries, and were fabricated to have the configurations shown in Table 2 below.

[0105] [Table 2]

[0106] According to the secondary battery using Example E1, the charge capacity is 16.8 [mAh] and the specific capacity is 12.7 [mAh / cm 2 In contrast, the secondary battery using Comparative Example C1 had a charge capacity of 12.6 [mAh] and a specific capacity of 9.4 [mAh / cm 2 In addition, the secondary battery using Comparative Example C2 had a charge capacity of 4.0 [mAh] and a specific capacity of 2.0 [mAh / cm 2 ] was the case.

[0107] A secondary battery using Comparative Example C1 in which the active material layer was made of carbon nanowalls had a charge capacity and specific capacity three times higher than Comparative Example C2 in which the active material layer was made of graphite. Example E1 in which the active material layer was made of carbon nanostructure 25 having extension 27 formed on base 26 had a charge capacity and specific capacity that were 30% or more higher than Comparative Example C1. This shows that the use of carbon nanostructure 25 having extension 27 as described in the above embodiment as an active material layer dramatically improves the battery performance of a secondary battery.

[0108] FIG. 16 is a photographed image of the secondary battery with the electrodes of Example E1 and Comparative Example C1 after charging was completed, taken from a direction perpendicular to the thickness direction of the metal substrate by a scanning electron microscope. In both Example E1 and Comparative Example C1, a layer of Li precipitated on the active material layer by a charging reaction was confirmed. However, as can be seen from these photographed images, the Li layer of Example E1 was denser than the Li layer of Comparative Example C1. In addition, the thickness Ta of the Li layer of Example E1 was about 50 μm, while the thickness Tb of the Li layer of Comparative Example C1 was about 32 μm, and the thickness of the Li layer of Example E1 was significantly larger than that of Comparative Example C1. From this, it can be seen that the charge capacity of the secondary battery using the electrode of Example E1 is dramatically improved compared to the secondary battery using the electrode of Comparative Example C1.

[0109] As described above, the electrode for an electricity storage device according to the present invention can significantly improve the battery performance of an electricity storage device.

[0110] The results of evaluation of the surfaces of the active material layers of Example E1 and Comparative Examples C3 and C4 by the sessile drop method will be described with reference to Fig. 17. Comparative Example C3 corresponds to an active material layer of carbon nanowalls formed by the CCP-CVD method, and Comparative Example C4 corresponds to an active material layer of carbon nanowalls formed by the RI-PECVD method. The CVD conditions for Comparative Examples C3 and C4 are almost the same as those shown in Table 1.

[0111] 17(a) is an explanatory diagram for explaining a method for measuring a contact angle by the sessile drop method. In the sessile drop method, a water droplet LQ is dropped on the surface SP to be evaluated, and the contact angle θ is determined as the angle on the water droplet LQ side between the tangent L to the surface of the water droplet LQ, which passes through the intersection of the surface of the water droplet LQ and the surface SP to be evaluated. The larger the contact angle θ, the higher the water repellency of the surface SP to be evaluated.

[0112] 17(b), (c), and (d) are images of the state when a water droplet LQ is dropped on the surface of the active material layer for Example E1, Comparative Example C3, and Comparative Example C4, respectively. The contact angle θ in Example E1 was about 150°, the contact angle θ in Comparative Example C3 was about 138°, and the contact angle θ in Comparative Example C4 was about 134°. Thus, the contact angle θ in Example E1 was the largest, indicating super water repellency. Carbon nanostructure 25 exhibiting such super water repellency can be applied to coating technology, such as oil separation and corrosion prevention technology.

[0113] 18 is a photographic image showing Comparative Examples C5 to C9 of active material layers produced by a manufacturing method different from that of the Examples. The carbon nanostructures of the active material layers of Comparative Examples C5 to C9 were formed by performing plasma treatment once or twice by RI-PECVD or CCP-CVD on the surface of copper foil as a metal substrate. The treatment conditions for the CVD method were the same as those shown in Table 1.

[0114] The carbon nanostructures of Comparative Example C5 were formed by a single plasma treatment in a CCP-CVD apparatus. In Comparative Example C5, carbon nanowalls were formed that were smaller in thickness, height, and length, and had a finer and more random structure.

[0115] The carbon nanostructure of Comparative Example C6 was formed by performing plasma treatment twice using a CCP-CVD apparatus. In Comparative Example C6, the amount of carbon nanowalls obtained by the second plasma treatment was increased as compared to the first plasma treatment, but a structure corresponding to the extension portion 27 described in the above embodiment was not obtained.

[0116] The carbon nanostructure of Comparative Example C7 was formed by a single plasma treatment in a RI-PECVD apparatus. The carbon nanostructure of Comparative Example C7 had a structure corresponding to the base 26 described in the above embodiment.

[0117] The carbon nanostructure of Comparative Example C8 was formed by performing plasma treatment twice using an RI-PECVD apparatus. In Comparative Example C8, the height of the carbon nanowalls formed in the first plasma treatment was increased by the second plasma treatment, but a structure equivalent to the extension 27 described in the above embodiment was not obtained.

[0118] The carbon nanostructure of Comparative Example C9 was formed by performing a first plasma treatment using a CCP-CVD apparatus and then a second plasma treatment using a RI-PECVD apparatus. In Comparative Example C9, the height of the carbon nanowalls was increased by the second plasma treatment, as in Comparative Example C8, but a structure equivalent to the extension portion 27 described in the above embodiment was not obtained.

[0119] From the results of comparative examples C5 to C9, it can be seen that in order to obtain the carbon nanostructure 25 described in the above embodiment, it is preferable to perform a first plasma treatment using an RI-PECVD apparatus and then a second plasma treatment using a CPC-CVD apparatus.

[0120] As described above, according to the manufacturing method of the present invention, an electrode for an electricity storage device can be obtained that can significantly improve the battery performance of an electricity storage device.

[0121] 2. Other embodiments: The present invention is not limited to the configurations of the above-mentioned embodiments and examples, and can be realized, for example, in the following forms. In the following, any configuration described as another embodiment is positioned as an example form for implementing the present invention, similar to the above-mentioned embodiments and examples.

[0122] 2-1. Other embodiment 1: The secondary battery using the electrode 20 of the above embodiment may be configured to involve metal ions other than lithium ions in charging and discharging. The secondary battery using the electrode 20 of the above embodiment may be configured to involve, for example, sodium (Na) ions, potassium (K) ions, magnesium (Mg) ions, etc. in charging and discharging.

[0123] 2-2. Other embodiment 2: The electrode 20 of the above embodiment may be used in an electricity storage device other than a secondary battery. The electrode 20 of the above embodiment may be used in, for example, an electric double layer capacitor. In this case, the electrode 20 may be used as both the positive electrode and the negative electrode of the electric double layer capacitor.

[0124] 3. Example of morphology: The present invention can be realized in the following forms.

[0125] [First embodiment] The first embodiment is provided as an electrode for an electricity storage device. The electrode for an electricity storage device of the first embodiment includes a metal substrate constituting a current collector, and an active material layer formed on the surface of the metal substrate and containing carbon as an active material, the active material layer being composed of a carbon nanostructure having a base portion in which graphene extending in an elongated manner in the thickness direction of the metal substrate is laminated, and a plurality of extension portions composed of the carbon and extending from the base portion. According to the first embodiment of the electrode for an electricity storage device, the active material layer is composed of a carbon nanostructure having a novel structure. This active material layer can increase the amount of metal ions involved in the charging reaction that precipitate as metal when the electricity storage device is charged. This can increase the charging capacity of the electricity storage device.

[0126] [Second Mode] In the electricity storage device electrode of the first mode, the carbon nanostructure may have a height of 0.5 μm or more. According to the electricity storage device electrode of the second embodiment, the battery performance of the electricity storage device to which it is applied can be further improved.

[0127] [Third Mode] In the electricity storage device electrode of the first or second mode, the average spacing between the carbon nanostructures in the active material layer may be 40 nm or less. According to the electricity storage device electrode of the third embodiment, the density of the carbon nanostructures in the active material layer is increased, and therefore the battery performance of the electricity storage device to which it is applied can be further improved.

[0128] [Fourth aspect] The fourth aspect is provided as a secondary battery. The secondary battery of the fourth aspect includes a first electrode constituted by the electrode for an electric storage device according to any one of the first, second, and third aspects, and a second electrode containing metal atoms that are ionized and move to the first electrode. According to the secondary battery of the fourth aspect, high battery performance can be obtained by applying an active material layer constituted by a carbon nanostructure having a novel structure.

[0129] [Fifth aspect] The fifth aspect is provided as a method for producing an electrode for an electrical device, which includes a step of growing, on a surface of a metal substrate, a base portion in which graphene is laminated and which extends in an elongated manner in a thickness direction of the metal substrate, by using a radical injection plasma CVD apparatus, and a step of forming, by using a capacitively coupled plasma CVD apparatus, a plurality of extension portions which are made of the carbon and extend from a surface layer of the base portion of the metal substrate. According to the manufacturing method of the fifth embodiment, it is possible to obtain an electrode having an active material layer composed of a carbon nanostructure having a novel structure. The carbon nanostructure has an extension portion, which can dramatically improve the battery performance of the power storage device. [Explanation of symbols]

[0130] Reference Signs List 10... secondary battery, 10a... secondary battery of comparative example, 11... container, 12... electrolyte, 15... separator, 16... first electrode chamber, 17... second electrode chamber, 20... first electrode (electrode for electricity storage device), 20a... electrode of comparative example, 21... metal substrate, 21a... first surface, 21b... second surface, 22... active material layer, 22a... active material layer of comparative example, 23... amorphous carbon layer, 25... carbon Nanostructure, 25a... carbon nanostructure of comparative example, 26... base, 27... extension, 28... metal atom, 30... second electrode, 31... positive electrode current collector, 31a... first surface, 31b... second surface, 32... positive electrode active material layer, 40... first processing device, 41... plasma generation chamber, 42... waveguide, 43... quartz window, 44... slot antenna, 45... micro generation unit, 46... radical source supply unit, 5 0... reaction chamber, 51... partition wall, 52... through hole, 53... gas flow path, 54... raw material gas supply section, 55... power supply section, 56... support base, 56s... placement surface, 57... heater, 58... exhaust section, 60... second processing device, 61... reaction chamber, 62... exhaust section, 65... raw material gas supply section, 66... ​​storage section, 67... flow rate control section, 67a... gas delivery device, 67b... flow rate adjustment valve, 68... introduction pipe, 70... support base, 71... susceptor, 72... quartz cover, 73... heater, 75... upper electrode, 76... power supply section, 81... vacuum gauge, 82... thermocouple, CCP... capacitively coupled plasma, CM... intermediate carbon nanostructure, GS... graphene, HDP... high density plasma, LQ... water droplet, MW... microwave, PM... protrusion, SP... evaluation target surface, SWP... surface wave plasma, VS... gap

Claims

1. An electrode for an electricity storage device, A metal substrate constituting a current collector; an active material layer formed on a surface of the metal substrate and containing carbon as an active material; Equipped with The active material layer is an electrode for an electricity storage device, the active material layer being composed of a carbon nanostructure having a base formed of laminated graphene extending in an elongated manner in the thickness direction of the metal substrate, and a plurality of extension portions composed of the carbon and extending from the base.

2. The electrode for an electricity storage device according to claim 1 , The height of the carbon nanostructure is 0.5 μm or more.

3. The electrode for an electricity storage device according to claim 1 , An electrode for an electricity storage device, wherein the average spacing between the carbon nanostructures in the active material layer is 40 nm or less.

4. A secondary battery, A first electrode constituted by the electrode for an electricity storage device according to any one of claims 1 to 3; a second electrode containing metal atoms that ionize and migrate to the first electrode; A secondary battery comprising:

5. A method for producing an electrode for an electricity storage device, comprising the steps of: A step of growing a base portion on a surface of a metal substrate, the base portion being composed of graphene that is elongated in a thickness direction of the metal substrate, by using a radical injection type plasma CVD apparatus; forming a plurality of extensions made of carbon and extending from a surface layer of the base of the metal substrate by a capacitively coupled plasma CVD apparatus; A manufacturing method comprising:

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