Electrode for power storage device, secondary battery, and method for manufacturing electrode for power storage device

Abstract

Provided is a novel electrode for a power storage device, which can improve the performance of a power storage device using carbon as an active material, and which can be mass-produced easily. This electrode for an electricity storage device is provided with: a metal substrate that constitutes a current collector; and an active material layer that is formed on the surface of the metal substrate and contains carbon as an active material. The surface of the active material layer has a fine uneven structure in which a plurality of fine particles are densely arranged; a carbon nanostructure is disposed over the entire surface layer of the granular body, and the carbon nanostructure is composed of graphene extending in an elongated manner toward the outside of the granular body.

Description

Technical Field

[0001] The present invention relates to an electrode for a power storage device, a secondary battery, and a method for producing the electrode for a power storage device. Background Art

[0002] As for chargeable and dischargeable storage devices, secondary batteries, double-layer capacitors, etc. are known. In some cases, electrodes for these storage devices use carbon as an active material disposed on the surface of the collector. For example, Japanese Patent No. 2668678 and Japanese Patent Publication No. 2010-9980 in the patent literature disclose a technology for forming an active material layer of a negative electrode of a lithium-ion secondary battery by graphite, carbon nanowalls, etc. When carbon nanowalls are used in the active material layer, it is expected that the battery performance of the storage device such as charging capacity and charging speed will be improved compared to the case of using graphite. Summary of the invention

[0003] [Problems to be solved by the invention]

[0004] However, the above-mentioned conventional technologies still cannot fully achieve the goal of high battery performance required of power storage devices.

[0005] In addition, the electrode with the active material layer of the carbon nano wall is often wound into a roll shape for transportation, storage, etc., and the carbon nano wall on the surface of the electrode is destroyed and falls off due to compression stress, shear stress, etc., so it is not easy to handle. Such a problem has become one of the reasons why the electrode with the active material layer of the carbon nano wall is difficult to mass produce. In this way, there is still room for improvement in terms of making it easy to manufacture and easy to mass produce for the electrode for the storage device using carbon as the active material.

[0006] [Methods used to solve the problem]

[0007] The inventors of the present invention have continuously studied electrodes for power storage devices using carbon as an active material, and finally successfully developed an active material layer that is different in shape from conventional graphite, carbon nanowalls, etc. and can significantly improve battery performance. The present invention can be implemented, for example, in the following forms.

[0008] The first form of the present invention is provided in the form of an electrode for a power storage device. The electrode for a power storage device of this form comprises: 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 surface of the active material layer has a fine concavo-convex structure, and the fine concavo-convex structure is densely arranged with a plurality of tiny granules; the entire surface layer covering the granules is arranged with a carbon nanostructure, and the carbon nanostructure is composed of graphene extending elongatedly toward the outside of the granules.

[0009] According to the present embodiment of the electrode for a power storage device, the surface area of ​​the carbon nanostructure contained in the active material layer can be increased, so the charging capacity of the power storage device can be increased. In addition, according to the present embodiment of the electrode for a power storage device, even if it is rolled into a roll, the destruction and shedding of the carbon nanostructure present in the concave part of the fine concavo-convex structure of the active material layer can be at least suppressed. Accordingly, the handling property of the electrode for a power storage device can be improved, and its mass production can be improved.

[0010] The present invention can be implemented in various forms other than electrodes for power storage devices, for example, it can be implemented in the form of a power storage device such as a secondary battery having electrodes for power storage devices, a method for manufacturing electrodes for power storage devices, a method for manufacturing power storage devices, a method for manufacturing collectors, a method for manufacturing active material layers, a manufacturing apparatus suitable for executing these manufacturing methods, a control program for controlling the manufacturing apparatus, a recording medium recording the control program, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 This is a schematic diagram showing the structure of a secondary battery including an electrode for a power storage device.

[0012] Figure 2 It is a schematic cross-sectional view showing the structure of an electrode for a power storage device.

[0013] Figure 3 It is a schematic plan view schematically showing the state of the surface of the active material layer.

[0014] Figure 4 This is a schematic diagram schematically showing the structure of the carbon nanostructure of the active material layer.

[0015] Figure 5 is a step flow chart showing the manufacturing steps of a secondary battery.

[0016] Figure 6 This is a schematic diagram showing the structure of a surface treatment device.

[0017] Figure 7 It is a schematic diagram showing the configuration of a production apparatus.

[0018] Figure 8 It is an explanatory diagram showing a photographic image according to the first embodiment.

[0019] Fig. 9 It is an explanatory diagram showing a photographic image according to the second embodiment.

[0020] Fig.10 It is an explanatory diagram showing photographic images of the third and fourth embodiments.

[0021] Fig.11 It is an explanatory diagram showing photographic images of the first and second comparative examples.

[0022] Fig.12 It is an explanatory diagram showing the evaluation test results of the battery performance of the first embodiment.

[0023] Fig.13 It is an explanatory diagram showing the evaluation test results of the battery performance of the second example.

[0024] Fig.14 It is an explanatory diagram showing the evaluation test results of the battery performance of the third example.

[0025] Fig.15 It is an explanatory diagram showing the evaluation test results of the battery performance of the fourth example.

[0026] Fig.16 It is an explanatory diagram showing the evaluation test results of the battery performance of the first comparative example.

[0027] Fig.17 It is an explanatory diagram showing the evaluation test results of the battery performance of the second comparative example.

[0028] Fig.18 It is an explanatory diagram showing the evaluation test results of the battery performance of Examples and Comparative Examples. DETAILED DESCRIPTION

[0029] Hereinafter, an embodiment of an electrode for a power storage device of the present invention will be described with reference to the drawings. Here, in this specification, "power storage device" refers to a chargeable and dischargeable power storage body such as a secondary battery, an electric double layer capacitor, and a device including the power storage body.

[0030] 1. Implementation Method

[0031] 1-1. Composition of secondary batteries:

[0032] Figure 1 1 is a schematic diagram showing the structure of a secondary battery 10 having an electrode 20 for a power storage device according to the present embodiment. The secondary battery 10 according to the present embodiment is a lithium ion secondary battery in which lithium ions participate in charge and discharge. The secondary battery 10 includes a container 11, an electrolyte 12, a separator 15, a first electrode 20, and a second electrode 30. Figure 1 In the figure, the container 11 is appropriately illustrated by a dotted chain line, and the partition 15 is illustrated by a dotted line.

[0033] The container 11 has an internal space filled with an electrolyte 12. The container 11 is made of a material that is not easily reactive to the electrolyte 12 and is liquid-tight. The electrolyte 12 has the property of being able to transfer metal ions involved in charging and discharging between the first electrode 20 and the second electrode 30. In the present embodiment, the electrolyte 12 is made of a solution in which a lithium salt is dissolved in an organic solvent, and can transfer lithium ions between the first electrode 20 and the second electrode 30. As for the lithium salt of the electrolyte 12, for example, lithium hexafluorophosphate (LiPF6) can be used. 6 ). In addition, as the organic solvent, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. can be used.

[0034] The separator 15 divides the internal space of the container 11 into a first electrode chamber 16 for accommodating the first electrode 20 and a second electrode chamber 17 for accommodating the second electrode 30. The separator 15 has electrical insulation and ion conductivity, electrically insulates the first electrode 20 from the second electrode 30, and allows lithium ions transmitted through the electrolyte 12 to penetrate. The separator 15 is formed, for example, of a resin film having a porous structure, a non-woven fabric, or the like.

[0035] The first electrode 20 corresponds to the electrode for the power storage device of the present embodiment. In the secondary battery 10 of the present embodiment, the first electrode 20 constitutes a negative electrode. The first electrode 20 includes a metal substrate 21 and an active material layer 22 .

[0036] The metal substrate 21 is a current collector. In the present embodiment, the metal substrate 21 is made of a copper (Cu) metal foil. The metal substrate 21 may also be made of a metal other than Cu. The metal substrate 21 may also be made of, for example, a Cu alloy, aluminum (Al), or an Al alloy. In addition, the metal substrate 21 may not be made of a metal foil, but may be made of, for example, a metal thin plate. The metal substrate 21 may not be made into a flat plate, but may be bent into various shapes such as a cylindrical shape, a wavy shape, etc.

[0037] 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. The details of the metal substrate 21 and the active material layer 22 of the first electrode 20 and the manufacturing method will be described later. Here, in the following description, the first electrode 20 will be simply referred to as "electrode 20".

[0038] The second electrode 30 is an electrode constituting the secondary battery 10. The second electrode 30 has a positive electrode collector 31 and a positive electrode active material layer 32. The positive electrode collector 31 is formed of a metal foil such as Al or titanium (Ti). The positive electrode collector 31 may also be formed of other metals and may have a shape other than a metal foil. The positive electrode collector 31 may not be formed in a flat shape, but may be bent into various shapes such as a cylindrical shape or a wavy shape.

[0039] 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 conductive auxiliary agent, a binder, and a positive electrode active material containing lithium atoms. The positive electrode active material layer 32 may also contain a thickening agent. For example, a ternary material may be used, and lithium cobalt oxide (LiCoO 2 ), lithium manganese oxide (LMO), lithium nickel oxide (NCA), etc. As for the conductive auxiliary agent, for example, acetylene black, carbon black, etc. can be used. As for the binder, for example, polyvinylidene fluoride (PVDF), styrene butadiene rubber (SBR), etc. can be used. As for the thickener, for example, carboxymethyl cellulose (CMC) can be used.

[0040] Reference Figure 2 , Figure 3 ,and Figure 4 The detailed structure of the electrode 20 according to the present embodiment will be described.

[0041] Figure 2 It is a schematic cross-sectional view schematically illustrating the cross-sectional structure of the electrode 20 in an arbitrary cross-section along the thickness direction. Figure 2 The structure of the electrode 20 on the first surface 21a side of the metal substrate 21 is extracted in the figure. The structure of the electrode 20 on the second surface 21b side of the metal substrate 21 is similar to Figure 2 The structure of the first surface 21a side shown is the same. Figure 2 In FIG. 1 , metal particles 26 described later are schematically shown in a substantially spherical shape.

[0042] Figure 3 It is a schematic plan view schematically illustrating the state of the surface of the active material layer 22 in an arbitrary region of the electrode 20 . Figure 3 In FIG. 1 , the outer peripheral contour of the granular body 23 when facing the surface of the active material layer 22 is shown by a dotted line.

[0043] Figure 4 1 is a schematic diagram schematically showing the structure of the carbon nanostructure 25 included in the active material layer 22 . Figure 4 In the figure, the surface of the metal substrate 21 is appropriately illustrated as a plane. Figure 4 In FIG. 1 , the graphene GS constituting the carbon nanostructure 25 is appropriately illustrated as a substantially rectangular sheet.

[0044] like Figure 2 As shown, the surface of the active material layer 22 of the electrode 20 has a fine concavo-convex structure CS, and the fine concavo-convex structure CS is formed by a plurality of densely arranged tiny granules 23. Here, "granules" refers to a part that can be identified as having a particle-like shape when viewed from a certain direction, and includes the concept of a convex part that is raised in a roughly spherical shape. In addition, in this specification, "particles" refers to the concept of tiny blocks of various shapes, which may not necessarily have a roughly spherical shape, but include the concept of a shape with an irregular concavo-convex structure on the surface. As Figure 3 As shown, when viewed along the thickness direction of the active material layer 22 , each granular body 23 of the active material layer 22 has a particle-like outer peripheral shape.

[0045] The average particle size of the granular body 23 is preferably 0.1 μm or more and 10.0 μm or less, more preferably 0.5 μm or more and 5.0 μm or less, and even more preferably 1.0 μm or more and 3.0 μm or less. With such an average particle size of the granular body 23, when the secondary battery 10 is charged, the precipitation of lithium described later becomes smooth, and the generation of lithium dendrites can be suppressed.

[0046] Here, for example, for a plurality of images taken with a scanning electron microscope or the like directly facing an arbitrary region of the active material layer 22 of the electrode 20, the maximum value of the width of each granular body 23 in a certain measurement direction is measured, and the measured values ​​are averaged to obtain the average particle size of the granular body 23. When the average particle size of the granular body 23 differs greatly due to different measurement directions, it is preferable to average the average particle sizes obtained in the predetermined plurality of measurement directions to calculate the average particle size of the granular body 23.

[0047] The height of the granular body 23 is preferably 0.5 μm or more and 8.0 μm or less, and more preferably 0.8 μm or more and 6.0 μm or less. For example, the height of the granular body 23 can be measured from a plurality of images taken from a direction perpendicular to the thickness direction of any region of the active material layer 22 of the electrode 20 using a scanning electron microscope or the like. The distance from the lower end to the upper end of each granular body 23 in the thickness direction of the active material layer 22 can be measured as the height of the granular body 23.

[0048] like Figure 2 As shown in FIG. 1 , a carbon nanostructure 25 composed of carbon atoms is disposed on the entire surface of each granular body 23. The carbon nanostructure 25 has electrical conductivity. Figure 4As shown, the carbon nanostructure 25 has a shape in which the graphene GS extends slenderly toward the outside of the granular body 23. The carbon nanostructure 25 has a multilayer structure in which multiple layers of graphene GS are stacked along its thickness direction. Graphene GS, also known as graphene sheet, is a six-membered ring structure of carbon, that is, a sheet-like substance having a thickness corresponding to one carbon atom, which is composed of a hexagonal lattice structure with carbon atoms as vertices.

[0049] The carbon nanostructure 25 is formed in a needle-like, plate-like, or wrinkled shape. The carbon nanostructure 25 can be interpreted as a structure of the same type as a carbon nanowall, a similar carbon nanosheet, a carbon nanoflower, etc. Since the carbon nanostructure 25 is a graphite-like substance, it has a higher conductivity than carbon materials such as activated carbon.

[0050] The carbon nanostructure 25 may not be formed by a single crystal of a six-membered ring of carbon. The graphene GS constituting the carbon nanostructure 25 may be a thin film mainly composed of carbon with a six-membered ring structure, rather than a complete graphene structure. The graphene GS may also have a mosaic structure mainly composed of carbon with a six-membered ring structure. The mosaic structure refers to a structure in which a plurality of regions composed of a six-membered ring structure of carbon are discretely arranged.

[0051] Here, the height H of the carbon nanostructure 25 corresponds to the length from the lower end of the substrate 21 side of the carbon nanostructure 25 to the top. In this embodiment, the height H of the carbon nanostructure 25 corresponds to the height from the surface of the amorphous carbon layer 29 to the top of the carbon nanostructure 25.

[0052] The average height H of the carbon nanostructure 25 is preferably greater than 100 nm. As described later, when the secondary battery 10 using the electrode 20 of this embodiment is charged, lithium will be precipitated on the surface of the carbon nanostructure 25, and the lithium ions will not be absorbed by the active material layer 22. If the average height H of the carbon nanostructure 25 is greater than 100 nm, when the secondary battery 10 is charged, lithium is easily dispersed and precipitated starting from the carbon nanostructure 25 and spread over the entire surface of the active material layer 22. Accordingly, the local dendritic growth of lithium can be suppressed, and the separator 15 can be suppressed from being damaged by the lithium grown by the dendritic growth.

[0053] The average height H of the carbon nanostructure 25 may be greater than 200 nm. However, if a higher carbon nanostructure 25 is to be formed, the time required to form the carbon nanostructure 25 will be correspondingly longer. Therefore, from the perspective of improving the productivity of the electrode 20, the average height H of the carbon nanostructure 25 is preferably 100×10 3 In addition, the average height H of the carbon nanostructure 25 is preferably 20×10 3 nm or less, more preferably 5×10 3 Below nm.

[0054] The average thickness W of the carbon nanostructure 25 is preferably, for example, 0.5 nm or more and 100.0 nm or less. The average thickness W is 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.

[0055] In the active material layer 22, the average spacing D between adjacent carbon nanostructures 25 is preferably greater than 10 nm and less than 500 nm. If the average spacing D is large, the density of the carbon nanostructure 25 in the active material layer 22 becomes smaller, and there is a possibility that the battery performance of the secondary battery 10 is reduced. If the average spacing D is small, the density of the carbon nanostructure 25 in the active material layer 22 becomes higher. However, if the density of the carbon nanostructure 25 is increased, the formation of the carbon nanostructure 25 is time-consuming and labor-intensive, and there is a possibility that the productivity of the electrode 20 is reduced. Here, on the photographic image of the carbon nanostructure 25 projected along the height direction, straight lines are drawn in a certain direction at a predetermined plurality of positions, and the value obtained by calculating the average value of the measured values ​​of the lengths of the line segments where each straight line passes through adjacent carbon nanostructures 25 is broken is taken as the average spacing D.

[0056] like Figure 2 As shown, a plurality of protrusions 28 are formed on the surface of the substrate 21 , and the plurality of protrusions 28 are composed of a plurality of minute metal particles 26 . Figure 2 In the example of FIG. 2 , the protrusion 28 is composed of a particle structure 27 formed by densely agglomerating metal particles 26. The particle structure 27 is a block formed by a plurality of metal particles 26 agglomerated in a bead-like manner. In addition to the particle structure 27 constituting the protrusion 28, the surface of the metal substrate 21 may also contain individual metal particles 26 constituting the protrusion 28.

[0057] Each of the granules 23 is formed by arranging the carbon nanostructures 25 extending from the surface of the metal particles 26 so as to cover the entire surface of the protrusions 28 formed by the metal particles 26. The active material layer 22 can also be interpreted as having a structure in which a plurality of granules 23 are aggregated into a bead-like stack with the metal particles 26 of the metal substrate 21 as the core.

[0058] The average particle size of the metal particles 26 constituting the particle structure 27 and the metal particles 26 constituting the protrusions 28 alone is preferably 0.1 μm or more and 5.0 μm or less, more preferably 0.5 μm or more and 3.0 μm or less. The average particle size of the metal particles 26 can be calculated by the same method as the average particle size of the granular body 23 described above.

[0059] The metal particles 26 preferably have a shape in which the height is larger than the particle diameter thereof, whether constituting the particle structure 27 or existing alone. The average height of the metal particles 26 is preferably greater than 0.5 μm and less than 3.0 μm. The average height of the metal particles 26 may also be greater than 0.6 μm and less than 2.5 μm. The height of the metal particles 26 is equivalent to the distance between the bottom and top ends of each metal particle 26 when the thickness direction of the metal substrate 21 is used as the height direction in a photographic image of the protrusion 28 taken from a direction perpendicular to the thickness direction of the metal substrate 21 by a scanning electron microscope.

[0060] The average value of the maximum width of the particle structure 27 is preferably 1.0 μm or more and 50.0 μm or less, and may be 1.5 μm or more and 30.0 μm or less. The maximum width of the particle structure 27 is the maximum value of the widths in all directions measured in a photographic image taken directly on the surface of the metal substrate 21 by a scanning electron microscope or the like.

[0061] The lower limit of the height of the particle structure 27 is preferably 0.5 μm or more, more preferably 0.8 μm or more. In addition, the lower limit of the height of the particle structure 27 is more preferably 1.0 μm or more, and particularly preferably 1.2 μm or more. The upper limit of the height of the particle structure 27 may be 10.0 μm or less, or 8.0 μm or less. The upper limit of the height of the particle structure 27 may also be 5.0 μm or less. Here, the height of the particle structure 27 is equivalent to the distance from the lowermost end of the particle structure 27 to the top in the thickness direction of the metal substrate 21.

[0062] As described above, the protrusions 28 include those formed by the individual metal particles 26 and those formed by the particle structure 27. The maximum width of each protrusion 28 is preferably 0.1 μm or more and 50.0 μm or less, and more preferably 0.5 μm or more and 30.0 μm or less. The maximum width of each protrusion 28 is the maximum value of the widths in all directions measured in a photographic image taken directly on the surface of the metal substrate 21 by a scanning electron microscope or the like.

[0063] The height of each protrusion 28 is preferably 0.5 μm or more and 10.0 μm or less, and more preferably 0.6 μm or more and 8.0 μm or less. The height of each protrusion 28 corresponds to the distance between the bottom and top ends of each protrusion 28 when the height direction is the thickness direction of the metal substrate 21 in a photographic image of the protrusion 28 taken from a direction perpendicular to the thickness direction of the metal substrate 21 by a scanning electron microscope.

[0064] The area of ​​the projection region of each protrusion 28 projected along the thickness direction of the metal substrate 21 is larger than 0.01 μm. 2And 10000μm 2 In addition, the density of the projection area of ​​the protrusion 28 when the metal substrate 21 is projected along the thickness direction is 1 piece / mm 2 More than but less than 10 8 Pieces / mm 2 The protrusions 28 of such a size can be easily formed by surface treatment of the metal foil by electrolytic deposition. In addition, according to the research of the inventors of the present invention, if the metal substrate 21 has protrusions 28 of such a size on the surface, the active material layer 22 having the above-mentioned granular body 23 can be easily formed by the CVD method.

[0065] like Figure 2 As shown in FIG. 2 , in this embodiment, the surface of the metal substrate 21 is covered with an amorphous carbon layer 29. Figure 4 As shown, the carbon nanostructure 25 is elongated upward from the amorphous carbon layer 29. The amorphous carbon layer 29 is the starting point of the growth of the carbon nanostructure 25. By forming the amorphous carbon layer 29 well, the formation state of the carbon nanostructure 25 can be improved. The film thickness of the amorphous carbon layer 29 is preferably, for example, 10 nm or more and 300 nm or less. The film thickness of the amorphous carbon layer 29 is more preferably 10 nm or more and 100 nm or less, and more preferably 12 nm or more and 30 nm or less.

[0066] 1-2. Battery reaction of secondary battery:

[0067] The chemical reaction during charge and discharge of the secondary battery 10 can be represented by the following reaction formula, for example. The positive electrode material is LiCoO 2 When , the reaction formula of the second electrode 30 which is the positive electrode can be expressed by the following formula (1). x represents the ratio of atoms in the reaction, which is a real number greater than 0 but less than 1.

[0068]

[0069] On the other hand, the reaction formula of the electrode 20 which is a negative electrode can be expressed by the following formula (2). As shown in formula (2), when the secondary battery 10 is charged, lithium is deposited in the electrode 20 .

[0070]

[0071] Here, in the case of a known negative electrode structure in which graphite is arranged on the surface of a flat metal substrate as an active material, during charging, in principle, one lithium ion is absorbed for each six carbon atoms to form lithium carbide (LiC 6 ). Therefore, the reaction formula of this well-known structure as a comparative example can be expressed as the following formula (3).

[0072] Familiar reaction formula:

[0073] As shown in the above formula (3), in the case of an electrode of a known structure using graphite as a negative electrode active material, the number of lithium ions that can be absorbed by charging depends on the number of carbon atoms contained in the active material layer.

[0074] In contrast, in the case of the electrode 20 used in the secondary battery 10 of the present embodiment, as shown in the above formula (2), theoretically, it is not limited by the number of carbon atoms in the active material layer 22, and charging can be performed as long as lithium can be precipitated. In other words, according to the electrode 20 of the present embodiment, in one charge or discharge, two or more lithium ions can participate in the charge and discharge reaction relative to one carbon atom. Accordingly, the secondary battery 10 of the present embodiment has an increased charge capacity because it has the electrode 20 as a negative electrode.

[0075] According to the electrode 20 of the present embodiment, the lithium precipitation caused by the charging reaction is promoted, and a lithium layer is easily formed uniformly on the surface of the active material layer 22, so that a stable and smooth charge and discharge reaction can be achieved, and the local generation of lithium dendrites can be suppressed to deteriorate the secondary battery 10. When considering the nucleation theory, the reason for obtaining such an effect can be inferred that lithium in the electrode 20 of the present embodiment is easily precipitated from the protrusions composed of the granular body 23 as the starting point.

[0076] In addition, according to the electrode 20 of this embodiment, since a fine concavo-convex structure CS is formed on the surface of the active material layer 22, even if the electrode 20 is rolled into a roll for transportation, etc., the carbon nanostructure 25 at a position lower than the top of the concavo-convex structure CS can be at least suppressed from being destroyed or falling off. Therefore, the handling of the electrode 20 in the manufacturing step of the secondary battery 10 becomes easy, the mass production of the electrode 20 becomes easy, and the manufacturing of the secondary battery 10 using the electrode 20 becomes easy.

[0077] 1-3. Method for manufacturing secondary battery:

[0078] Figure 5 1 is a flowchart showing the steps of manufacturing the secondary battery 10. Steps P1 and P2 are steps of manufacturing the electrode 20. Step P1 is equivalent to the step of preparing the metal substrate 21. In the present embodiment, in step P1, a surface treatment is performed on a substrate BM having a flat surface by electrolysis, thereby preparing a metal substrate 21 having a protrusion 28 composed of tiny metal particles 26 formed on the surface. The substrate BM is, for example, a metal foil, a metal thin plate, etc. In the present embodiment, the substrate BM is a copper foil.

[0079] Figure 6: is a schematic diagram showing the structure of the surface treatment device 50 used in step P1. The surface treatment device 50 includes a feed roller 51 on which the substrate BM before treatment is wound, a plurality of guide rollers 52 for guiding the conveyance of the substrate BM, and a winding roller 53 for winding the substrate BM after surface treatment, as a conveying unit for the substrate BM. In addition, the surface treatment device 50 further includes an electrolytic bath 55 filled with an electrolyte 56 and an electrode plate 58 provided in the electrolytic bath 55, as an execution unit for electrolytic deposition. In addition, although not shown in the figure, the surface treatment device 50 includes a power supply unit for energizing the electrode plate 58 and the substrate BM.

[0080] The substrate BM is drawn out from the delivery roller 51, guided by a plurality of guide rollers 52, and conveyed to the winding roller 53. One of the guide rollers 52 is disposed in the electrolytic bath 55. Accordingly, the substrate BM is conveyed into the electrolytic bath 55, and after being immersed in the electrolyte 56 in the electrolytic bath 55, it is turned back in the electrolytic bath 55 and conveyed out of the electrolytic bath 55. While the substrate BM passes through the electrolyte 56 in the electrolytic bath 55, the surface treatment by electrolytic deposition described below is applied to the surface of the substrate BM.

[0081] The electrode plate 58 in the electrolytic bath 55 contains metal atoms of the same type as the metal constituting the substrate BM. In the present embodiment, the electrode plate 58 is made of crude copper. The electrode plate 58 is arranged to face the surface of the substrate BM transported into the electrolytic bath 55. The electrode plate 58 is preferably arranged substantially parallel to the surface of the substrate BM.

[0082] During the transportation of the substrate BM, a voltage is applied by the power supply unit with the electrode plate 58 as an anode and the substrate BM as a cathode. Accordingly, the Cu of the electrode plate 58 is oxidized and dissolved into Cu ions in the electrolyte 56, moves toward the substrate BM, and is reduced and precipitated on the surface of the substrate BM. Fine metal particles 26 are formed successively on the surface of the substrate BM by the precipitated Cu, and the protrusions 28 are formed by these metal particles 26. The metal particles 26 are locally densely gathered to form the protrusions 28 to form the particle structure 27. The protrusions 28 are formed in a state of covering the entire surface of the substrate BM.

[0083] The surface treatment of step P1 is performed on both sides of the substrate BM. Thus, the metal substrate BM having fine concavo-convex structures CS on both sides is completed. The treatment conditions such as the type, concentration, energization voltage, and conveying speed of the substrate BM of the electrolyte 56 in the surface treatment device 50 in step P1 can be appropriately adjusted to form the metal particles 26, protrusions 28, etc. of the above-mentioned size.

[0084] Here, the surface treatment device 50 may be configured to arrange a plurality of guide rollers 52 in one electrolytic bath 55, thereby repeatedly immersing the substrate BM in the electrolyte 56 for one electrolytic bath 55. Alternatively, the surface treatment device 50 may also include a plurality of electrolytic baths 55 and arrange guide rollers 52 in each electrolytic bath 55, and have a configuration for conveying the substrate BM so that it can be repeatedly immersed in the electrolyte 56 of each electrolytic bath 55.

[0085] In step P2, an active material layer 22 is formed on the surface of the metal substrate 21 by CVD (Chemical Vapor Deposition). In step P2, a carbon nanostructure 25 is generated on the surface of the metal substrate 21 by plasma treatment, and an active material layer 22 is formed on the surface, the active material layer 22 having a fine concave-convex structure CS formed by densely arranging a plurality of tiny granular bodies 23 that cover the entire surface of the carbon nanostructure 25.

[0086] Figure 7 1 is a schematic diagram showing the structure of a manufacturing apparatus 60 suitable for executing the plasma treatment of step P2. The manufacturing apparatus 60 is a capacitively coupled plasma (CCP: Capacitively Coupled Plasma) CVD apparatus.

[0087] The manufacturing apparatus 60 includes a reaction chamber 61, an exhaust unit 62, a raw material gas supply unit 65, a substrate support unit 70, an upper electrode 75, and a power supply unit 76. The manufacturing apparatus 60 further includes a vacuum gauge 81 and a thermocouple 82 as measuring units.

[0088] The reaction chamber 61 has an airtight structure capable of being maintained in a vacuum state. The reaction chamber 61 is connected to an exhaust unit 62 and a raw material gas supply unit 65 .

[0089] The exhaust unit 62 includes an exhaust pipe 63 that is introduced into the reaction chamber 61, and a vacuum pump 64 that is connected to the exhaust pipe 63. During the plasma treatment, the vacuum pump 64 sucks the remaining gas that is not consumed in the reaction in the reaction chamber 61 through the exhaust pipe 63, and maintains the vacuum degree in the reaction chamber 61 within the range of 5 to 2000 mTorr (0.65 to 267 Pa). Here, the vacuum degree of the reaction chamber 61 is measured by a vacuum gauge 81.

[0090] The raw material gas supply unit 65 supplies the raw material gas to be consumed in the plasma process to the reaction chamber 61. The raw material gas supply unit 65 includes a raw material gas storage unit 66, a flow rate control unit 67, and a raw material introduction pipe 68.

[0091] The raw material gas storage unit 66 stores a plurality of gases as raw material gases for plasma processing according to the types of gases. In the manufacturing apparatus 60, a carbon-based gas containing carbon to form the carbon nanostructure 25 and a reaction-promoting gas that helps the growth of the carbon nanostructure 25 are used as raw material gases. The carbon-based gas is, for example, methane (CH 4 ), ethane hexafluoride (C 2 F 6 ) etc. The promoting reaction gas promotes the plasma formation of the carbon-based gas by the Penning effect during the plasma treatment. In addition, the promoting reaction gas is ionized during the plasma treatment and collides with the metal substrate 21 which is the treatment object, thereby forming a core which becomes the growth starting point of the carbon nanostructure 25. The promoting reaction gas is, for example, hydrogen (H 2 ), argon (Ar), etc. In the raw material gas storage section 66, these multiple gases are stored individually in tanks (not shown).

[0092] The flow control unit 67 includes a gas delivery device 67a and a flow control valve 67b. The gas delivery device 67a and the flow control valve 67b are respectively provided in individual pipes of a plurality of gases connected to the raw material gas storage unit 66. The gas delivery device 67a is constituted by, for example, an ejector, a pump, etc., and delivers the gas from the raw material gas storage unit 66 at a predetermined pressure. The gas delivered by the gas delivery device 67a is controlled in flow by the flow control valve 67b. The various gases whose flow is adjusted by the flow control valve 67b are combined in the raw material introduction pipe 68. The raw material introduction pipe 68 introduces the raw material gas obtained by mixing these various gases in a predetermined ratio into the reaction chamber 61.

[0093] A substrate support 70 is provided in the reaction chamber 61. The substrate support 70 supports the metal substrate 21 prepared in step P1. The substrate support 70 includes a susceptor 71, a quartz cover 72, and a heater 73. The susceptor 71 constitutes a support base for the metal substrate 21. The metal substrate 21 to be processed is arranged on the susceptor 71. The susceptor 71 is grounded. As described later, since a high frequency voltage is used during plasma processing, the susceptor 71 may also be arranged in a floating manner.

[0094] The heat sink 71 is disposed on the quartz cover 72, and a heater 73 is provided below the quartz cover 72. The heater 73 is protected by the quartz cover 72. In addition, the quartz cover 72 supports the heat sink 71 and prevents the heater 73 from directly contacting the heat sink 71.

[0095] During the plasma treatment, the metal substrate 21 is heated by receiving the radiant heat of the heater 73 through the heat receiver 71. The thermocouple 82 measures the heating temperature of the heater 73. During the plasma treatment, the heating of the metal substrate 21 by the heater 73 is controlled according to the temperature measured by the thermocouple 82. In the present embodiment, the heater 73 is controlled to a predetermined heating temperature within the range of above room temperature (RT) and below 700°C. Controlling the heating temperature to RT means stopping the control of driving the heater 73.

[0096] An upper electrode 75 is provided at the upper portion of the reaction chamber 61. The upper electrode 75 is provided on the heat sink 71 so as to face the metal substrate 21 to be processed. The upper electrode 75 is preferably provided substantially parallel to the metal substrate 21. The distance between the upper electrode 75 and the heat sink 71 is, for example, about 1 to 5 cm. The upper electrode 75 is connected to a power supply device 76 provided outside the reaction chamber 61.

[0097] The power supply device 76 is a high-frequency power supply device. When the raw material gas is supplied from the raw material gas storage unit 66 to the reaction chamber 61, the power supply device 76 applies a high-frequency voltage to the upper electrode 75, so that a high-density capacitively coupled plasma is generated in the reaction chamber 61. By generating this high-density plasma, free radicals are generated in the reaction chamber 61. During the plasma treatment, the carbon nanostructure 25 is generated on the entire surface of the metal substrate 21 by utilizing these free radicals. After the plasma treatment starts, first, the amorphous carbon layer 29 is formed to cover the entire surface of the metal substrate 21, and then the carbon nanostructure 25 grows with the metal particles 26 covered by the amorphous carbon layer 29 as the growth starting point.

[0098] Here, generally speaking, when the carbon nanowall is formed on the flat surface of the metal substrate by the CVD method, the heating temperature of the metal substrate is controlled to a high temperature of 700°C or higher. As shown in this embodiment, if a convex portion such as a metal particle 26 is formed on the surface of the metal substrate 21, since the metal particle 26 becomes the growth starting point of the carbon nanostructure 25, the growth of the carbon nanostructure 25 is promoted more than on a flat surface. Therefore, even if the heating temperature of the metal substrate 21 is controlled to be above RT as described above by the heater 73, the carbon nanostructure 25 can still be smoothly formed under a relatively low temperature condition of below 700°C. Here, the upper limit of the heating temperature of the metal substrate 21 by the heater 73 may be less than 700°C, and may be below 600°C, or may be below 500°C. The heating temperature of the metal substrate 21 by the heater 73 may be controlled to be below 400°C, or may be controlled to RT.

[0099] In step P2, a metal substrate 21 to be processed is arranged in the reaction chamber 61, and an active material layer 22 having a carbon nanostructure 25 is formed on the surface of the metal substrate 21 by plasma treatment in the manufacturing device 60. Here, although not shown, the metal substrate 21 to be processed in the manufacturing device 60 is set to be wound into a roll outside the reaction chamber 61. During the plasma treatment, the metal substrate 21 is continuously pulled out of its roll and placed in the reaction chamber 61 and supported by the heat holder 71 and then transported to the outside of the reaction chamber 61. In the manufacturing device 60, the active material layer 22 is formed on the surface of the metal substrate 21 passing through the reaction chamber 61 by plasma treatment.

[0100] In step P3, a second electrode 30 serving as a positive electrode is manufactured. In step P4, Figure 1 As shown, the first electrode 20 and the second electrode 30 are assembled in the container 11 filled with the electrolyte 12. Through the above steps, the secondary battery 10 is completed.

[0101] In summary, according to the manufacturing steps of the present embodiment, in step P1, the metal substrate 21 can be efficiently manufactured by using the surface treatment of electrolytic deposition. In addition, in step P2, since the surface of the metal substrate 21 is provided with a protrusion 28, the active material layer 22 having a plurality of granular bodies 23 formed on the surface can be efficiently generated under relatively low temperature conditions. As described above, even if the electrode 20 prepared in steps P1 and P2 is rolled into a roll for transportation, the destruction and falling off of the carbon nanostructure 25 of the active material layer 22 can be suppressed, so it is easy to handle. Therefore, the mass productivity of the electrode 20 is improved, and the manufacture of the secondary battery 10 using the electrode 20 becomes easy.

[0102] [Example]

[0103] Reference Figure 8 , Fig. 9 , Fig.10 ,and Fig.11 Examples E1, E2, E3, and E4 of the electrode 20 according to the present embodiment and comparative examples C1 and C2 thereof will be described.

[0104] Figure 8 Parts (a) and (b) of FIG. 1 show photographic images of the surface of the metal substrate 21 constituting the current collector of Example E1. Fig. 9 Parts (a) and (b) of FIG. 1 show photographic images of the surface of the metal substrate 21 constituting the current collector of Example E2. Figure 8 Part (a) and Fig. 9 Part (a) is an image of the protrusion 28 when viewed from a direction perpendicular to the thickness direction of the metal substrate 21 , taken by a scanning electron microscope. Figure 8 Part (b) of Fig. 9 Part (b) is an image of the surface of the metal substrate 21 captured along the thickness direction of the metal substrate 21 using a scanning electron microscope. Figure 8 Part (b) of Fig. 9 The image of the portion (b) corresponds to an image of a projection region where the protrusion 28 is projected in the thickness direction of the metal substrate 21 .

[0105] The metal substrate 21 of Examples E1 and E2 is made by using copper foil as a base material and performing the above-mentioned surface treatment using electrolytic deposition. Figure 8 Part (a) and Fig. 9 As shown in part (a) of FIG. 1 , the protrusion 28 includes a particle structure 27 having a structure in which metal particles 26 are densely aggregated, a protrusion formed by individual metal particles 26, and the like. In Example E1, the particle structure 27 is as follows Figure 8 As shown in part (b) of FIG. 2 , the metal substrate 21 is distributed on the entire surface. On the other hand, in Example E2, as shown in FIG. Figure 8 As shown in part (b) of FIG. 2 , metal particles 26 that individually constitute the protrusions 28 are dispersedly arranged over the entire surface of the metal substrate 21 , and the particle structures 27 that constitute the protrusions 28 exist between the individual metal particles 26 .

[0106] like Figure 8 As shown in part (b) of the embodiment E1, the particle size of the metal particles 26 constituting the particle structure 27 is approximately in the range of 0.5 to 5.0 μm. Fig. 9 As shown in part (b) of FIG. 2 , in Example E2, the particle diameters of the metal particles 26 constituting the protrusions 28 alone and the metal particles 26 constituting the particle structure 27 are generally within the range of 0.1 to 5.0 μm.

[0107] like Figure 8 As shown in part (b) of the embodiment E1, the maximum width of the particle structure 27 is approximately in the range of 5.0 to 50.0 μm. Fig. 9 As shown in part (b) of FIG. 1 , in Example E2, the maximum width of the particle structure 27 is approximately in the range of 1.0 to 10.0 μm.

[0108] As described above, the maximum width of the protrusion 28 in the metal substrate 21 of Examples E1 and E2 is generally within the range of 0.1 to 50.0 μm.

[0109] like Figure 8 As shown in part (a) of the embodiment E1, the height of the metal particles 26 constituting the particle structure 27 is approximately in the range of 0.5 to 2.5 μm. Fig. 9As shown in part (a) of FIG. 1 , in Example E2, the heights of the metal particles 26 constituting the protrusions 28 alone and the metal particles 26 constituting the particle structure 27 are generally within the range of 0.5 to 3.0 μm.

[0110] like Figure 8 As shown in part (a) of FIG. 1 , in Example E1, the height of the particle structure 27 is approximately within the range of 3.0 to 10.0 μm or less. Fig. 9 As shown in part (a) of FIG. 1 , in Example E2, the height of the metal particles 26 constituting the protrusions 28 alone is approximately in the range of 0.5 to 5.0 μm. In Example E2, the height of the particle structure 27 is approximately in the range of 1.0 to 8.0 μm.

[0111] As described above, the height of the protrusions 28 in the metal substrates 21 of Examples E1 and E2 is generally within the range of 0.5 to 10.0 μm.

[0112] In either of the embodiments E1 and E2, the projection area of ​​the protrusion 28 along the thickness direction of the metal substrate 21 is larger than 0.01 μm. 2 And 10000μm 2 In addition, the density of the projection area of ​​the protrusion 28 when the metal substrate 21 is projected along the thickness direction is 1 piece / mm 2 More than but less than 10 8 Pieces / mm 2 Here, the projection area of ​​the protrusion 28 is equivalent to Figure 8 The area of ​​the darker shaded region surrounded by the peripheral contour line that appears in the photographic image of part (b).

[0113] Figure 8 Parts (c) and (d) of FIG. 1 show photographic images of the active material layer 22 in Example E1. Fig. 9 Parts (c) and (d) of FIG. 1 show photographic images of the active material layer 22 in Example E2. Fig.10 Parts (a) and (b) of FIG. 1 show photographic images of the active material layer 22 in Example E3, respectively. Fig.11 Parts (c) and (d) of FIG. 1 show photographic images of the active material layer 22 in Example E4, respectively. Figure 8 Part (c) of Fig. 9 Part (c) of Fig.10 part (a) of Fig.10 Part (c) is an image of the granular bodies 23 of the active material layer 22 when viewed from a direction perpendicular to the thickness direction of the electrode 20 , taken using a scanning electron microscope. Figure 8 Part (d) of Fig. 9Part (d) of Fig.10 part (b) of Fig.10 Part (d) is an image of the granular bodies 23 on the surface of the active material layer 22 taken along the thickness direction of the electrode 20 using a scanning electron microscope.

[0114] Embodiments E1, E3, and E4 are obtained by Figure 8 The active material layer 22 is formed on the surface of the metal substrate 21 shown in parts (a) and (b) by the CVD method under the conditions shown in Table 1 below. Example E2 is prepared by Fig. 9 The surface of the metal substrate 21 shown in parts (a) and (b) is made by forming an active material layer 22 by a CVD method under the conditions shown in Table 1 below. The distance between the upper electrode 75 and the metal substrate 21 is 3 cm. In Examples E1 and E4, the CCP-CVD method is used. In Examples E2 and E3, unlike in Examples E1 and E4, hydrogen is plasma-treated with a microwave power source.

[0115] During the plasma treatment, as shown in Table 1, the heating temperature of the metal substrate 21 caused by the heater 73 is controlled to 700° C. in both Examples E1 and E2, to RT in Example E3, and to 400° C. in Example E4. Here, the “heating temperature of the metal substrate” in Table 1 refers to the measured value of the temperature near the heater 73 measured by the thermocouple 82, which is different from the temperature of the metal substrate 21. The temperature of the metal substrate 21 is usually affected by plasma irradiation, and is higher than RT even when not heated by the heater 73.

[0116] Table 1

[0117]

[0118] like Figure 8 , Fig. 9 ,and Fig.10 As shown, a plurality of fine granules 23 are densely arranged on the surface of the active material layer 22 of Examples E1, E2, E3, and E4, thereby forming a fine concavoconvex structure CS. Each granule 23 is three-dimensionally dispersed and formed along the thickness direction and surface direction of the electrode 20.

[0119] Figure 8 , Fig. 9 ,and Fig.10 In the image shown, the carbon nanostructures 25 appear in white streaks. In any of Examples E1, E2, E3, and E4, the carbon nanostructures 25 are formed to cover the entire surface layer of the granular bodies 23 .

[0120] like Figure 8As shown in part (d) of the embodiment E1, the particle size of each granular body 23 is generally within the range of 0.5 μm or more and 5.0 μm or less. Fig. 9 As shown in part (d) of the embodiment E2, the particle size of each granular body 23 is generally within the range of 0.5 μm or more and 5.0 μm or less. Fig.10 As shown in part (b) of the embodiment E3, the particle size of each granular body 23 is generally within the range of 0.5 μm or more and 5.0 μm or less. Fig.10 As shown in part (d), in Example E4, the particle size of each granular body 23 is generally within the range of 0.1 μm or more and 2.0 μm or less. The particle size of each granular body 23 here is the maximum value of the width of each granular body 23 in the width direction of the image.

[0121] like Figure 8 As shown in part (c) of the embodiment E1, the height of each granular body 23 is generally within the range of 0.5 μm or more and 3.0 μm or less. Fig. 9 As shown in part (c) of the embodiment E2, the height of each granular body 23 is generally within the range of 1.5 μm or more and 6.0 μm or less. Fig.10 As shown in part (a) of the embodiment E3, the height of each granular body 23 is generally within the range of 1.0 μm or more and 4.0 μm or less. Fig.10 As shown in part (c) of FIG. 1 , in Example E4, the height of each granular body 23 is generally within the range of 0.5 μm to 2.0 μm.

[0122] In any one of the embodiments E1, E2, E3, and E4, the height H of the carbon nanostructure 25 is approximately 80 to 200 nm. In any one of the embodiments E1, E2, E3, and E4, the thickness W of the carbon nanostructure 25 is approximately in the range of 1 to 10 nm. In addition, in any one of the embodiments E1, E2, E3, and E4, the interval D of the carbon nanostructure 25 is approximately in the range of 10 nm or more and 500 nm or less.

[0123] Figure 8 , Fig. 9 ,and Fig.10 Although it cannot be confirmed in the image, in Examples E1, E2, E3, and E4, an amorphous carbon layer 29 is formed under the carbon nanostructure 25. The film thickness of the amorphous carbon layer 29 is generally in the range of 10 nm to 300 nm.

[0124] As shown in Table 1, in Examples E3 and E4, the heating temperature of the metal substrate 21 by the heater 73 is controlled to be less than 700° C. Even under this temperature condition, the carbon nanostructure 25 can be formed in the same manner as in Examples E1 and E2. In addition, as described later, the electrodes of Examples E3 and E4 do not significantly differ from the electrodes of Examples E1 and E2 in terms of the battery performance of the secondary battery.

[0125] Fig.11 Parts (a) and (b) show photographic images of the active material layer of Comparative Example C1, respectively. Fig.11 Part (a) is an image of the active material layer of Comparative Example C1 taken from a direction perpendicular to the thickness direction of the active material layer using a scanning electron microscope. Fig.11 Part (b) is an image of the surface of the active material layer of Comparative Example C1 taken from a direction facing the surface of the active material layer using a scanning electron microscope.

[0126] The active material layer of Comparative Example C1 was formed by CVD under the conditions shown in Table 1 using a copper foil having a flat surface that was not subjected to surface treatment for electrolytic deposition as in Example 1 as a metal substrate. In the CVD method of Comparative Example C1, hydrogen was plasma treated with a microwave power source in the same manner as in Example E2.

[0127] like Fig.11 As shown in parts (a) and (b) of FIG. 1 , in comparative example C1, the active material layer is formed by carbon nanowalls. Fig.11 As shown in part (a) of FIG. 1 , in Comparative Example C1, the carbon nanowalls are formed to have almost the same height of about 1.0 μm. Fig.11 As shown in part (b) of FIG. 1 , in Comparative Example C1, the carbon nanowall is formed in an irregular mesh shape covering the entire surface of the metal substrate.

[0128] Fig.11 Part (c) shows a photographic image of the active material layer of the electrode of Comparative Example C2. Fig.11 Part (c) is an image of the surface of the active material layer of Comparative Example C1 taken from a direction facing the surface of the active material layer using a scanning electron microscope. Comparative Example C2 has the same configuration as Comparative Example C1 in which a graphite layer is formed on the surface of a flat metal substrate.

[0129] Figures 12 to 17 It is an explanatory diagram showing the results of a test for evaluating the battery performance of secondary batteries using the electrodes of Examples E1, E2, E3, and E4 and Comparative Examples C1 and C2 as negative electrodes.

[0130] Figures 12 to 15 The graphs obtained using the secondary batteries of Examples E1, E2, E3, and E4 are shown in FIG. Fig.16 and Fig.17Graphs obtained using the secondary batteries of Comparative Examples C1 and C2 are shown respectively. Figures 12 to 17 In FIG. 1 , the relationship between the voltage and the charge capacity of the secondary battery during charging is shown as a solid line graph, and the relationship between the voltage and the charge capacity of the secondary battery during discharging is shown as a dot chain line graph. Fig.18 The charge capacity and specific capacity of the secondary batteries using Examples E1 and E2 and Comparative Examples C1 and C2 are shown in bar graphs, respectively. In this evaluation test, both the charge current and the discharge current were set to 0.5 mA.

[0131] The secondary batteries used in Examples E1, E2, E3, E4 and Comparative Examples C1 and C2 are lithium ion secondary batteries, and are manufactured with the configurations shown in Table 2 below.

[0132] Table 2

[0133]

[0134] like Figures 12 to 18 As shown, according to the secondary battery of Comparative Example C2 using an active material layer having graphite, the charge capacity is 4.0 [mAh] and the specific capacity is 2.0 [mAh / cm 2 In addition, the secondary battery of Comparative Example C1 using an active material layer having a carbon nanowall of the same thickness had a charge capacity of 12.6 [mAh] and a specific capacity of 9.4 [mAh / cm 2 ]. Thus, when the carbon nanowall is applied to the active material layer of the negative electrode, the battery performance of the secondary battery can be significantly improved compared to the case where graphite is applied to the active material layer.

[0135] However, according to the secondary battery using Example E2, the charge capacity was 14.3 [mAh] and the specific capacity was 11.0 [mAh / cm 2 In addition, according to the secondary battery using Example E1, the charge capacity is 15.0 [mAh] and the specific capacity is 11.3 [mAh / cm 2 Even when using the secondary batteries of Examples E3 and E4, the charge capacity is 14.0 [mAh] or more and the specific capacity is 11.0 [mAh / cm 2 ] or more. Thus, for any one of Examples E1, E2, E3, and E4, the battery performance is significantly improved compared to the secondary battery of Comparative Example C2 using an active material layer having a carbon nanowall. The reason for this result is believed to be that the surface area of ​​the carbon nanostructure 25 in the active material layer 22 of Examples E1, E2, E3, and E4 is much larger than the surface area of ​​the carbon nanowall in the active material layer of Comparative Example C2.

[0136] In summary, it can be seen that the electrode for a power storage device according to the present invention can significantly improve the battery performance of the power storage device.

[0137] 2. Other implementation methods

[0138] The present invention is not limited to the configurations of the above-mentioned embodiments or examples, and can also be implemented in the following forms, for example. The configurations described below in other embodiments are all considered as one form of implementation of the present invention in the same manner as the above-mentioned embodiments or examples.

[0139] 2-1. Other implementation methods 1:

[0140] The secondary battery using the electrode 20 of the above embodiment may also be configured to allow metal ions other than lithium ions to participate in charge and discharge. The secondary battery using the electrode 20 of the above embodiment may also be configured to allow, for example, sodium (Na) ions, calcium (K) ions, magnesium (Mg) ions, etc. to participate in charge and discharge.

[0141] 2-2. Other implementation methods 2:

[0142] The electrode 20 of the above embodiment can also be used in power storage devices other than secondary batteries. The electrode 20 of the above embodiment can also be used in, for example, an electric double layer capacitor. In this case, the electrode 20 can be used as both the positive electrode and the negative electrode of the electric double layer capacitor.

[0143] 2-3. Other implementation methods 3:

[0144] In the manufacturing method of the electrode 20 described in the above embodiment, the base material BM of the metal substrate 21 may be subjected to surface treatment by a method other than electrolytic deposition in step P1. The protrusions 28 of the metal substrate 21 may be formed by, for example, surface treatment by CVD, oxidation treatment of the metal substrate, plasma treatment, etc. In addition, the protrusions 28 of the metal substrate 21 may be formed by, for example, a mechanical treatment of pressing the surface of the metal substrate 21 by pressing a roll having a plurality of protrusions on the surface.

[0145] 2-4. Other implementation methods 4:

[0146] In the manufacturing method of the electrode 20 described in the above embodiment, plasma treatment of a CVD method other than the CCP-CVD method may be performed in step P2. In step P2, the carbon nanostructure 25 may be generated by, for example, RI-CVD method, ICP-CVD method, LIA-CVD method, etc.

[0147] 3. Type example:

[0148] The present invention can be implemented in the following aspects.

[0149] [First Form]

[0150] An electrode for a power storage device comprises: a metal substrate, which constitutes a current collector; and an active material layer, which is formed on the surface of the metal substrate and contains carbon as an active material; the surface of the active material layer has a fine concave-convex structure, and the fine concave-convex structure is densely arranged with a plurality of tiny granules; a carbon nanostructure is arranged on the entire surface layer covering the granules, and the carbon nanostructure is composed of graphene extending elongatedly toward the outside of the granules.

[0151] According to the first type of the storage device electrode, the surface area of ​​the carbon nanostructure contained in the active material layer can be increased, so the charging capacity of the storage device can be increased. In addition, according to the first type of storage device electrode, even if it is rolled into a roll, it can at least suppress the destruction and shedding of the carbon nanostructure present in the concave part of the fine concavo-convex structure of the active material layer. Accordingly, the handling property of the storage device electrode can be improved, and its mass production can be improved.

[0152] [Second Form]

[0153] In the first type of the electrode for the storage device, a plurality of protrusions composed of tiny metal particles are formed on the surface of the metal substrate; the granular body can be formed by configuring the carbon nanostructure formed by extending from the surface of the metal particles to cover the entire surface of the protrusions.

[0154] According to the second embodiment of the electrode for a power storage device, the carbon nanostructure can be easily generated starting from the metal particles of the metal substrate, so that the granular body of the active material layer can be formed in a more preferable state.

[0155] [Third Form]

[0156] In the second aspect of the electrode for a power storage device, the protrusion may include a particle aggregate in which a plurality of the metal particles are densely aggregated.

[0157] According to the third aspect of the electrode for a power storage device, the granular body of the active material layer can be formed more easily and in a more preferable state by the particle assembly of the metal substrate.

[0158] [Fourth Form]

[0159] In the second or third embodiment of the power storage device electrode, the projection area of ​​the protrusion along the thickness direction of the metal substrate is larger than 0.01 μm. 2 And 10000μm 2 Hereinafter, the density of the projection area of ​​the protrusion when the metal substrate is projected along the thickness direction is 1 piece / mm 2 More than but less than 10 8 Pieces / mm2 .

[0160] According to the fourth aspect of the electrode for a power storage device, since the metal substrate has the protrusions of a more preferred size, the granular body of the active material layer can be formed in a more preferred state.

[0161] [Fifth Form]

[0162] In the electrode for a power storage device of any one of the first to fourth aspects, the average particle size of the granular body may be not less than 0.1 μm and not more than 10.0 μm.

[0163] According to the fifth aspect of the electrode for a power storage device, the generation of dendrites in the power storage device can be suppressed.

[0164] [Sixth Form]

[0165] The sixth embodiment is provided as a secondary battery. The secondary battery of the sixth embodiment comprises: a first electrode, which is formed by the electrode for the power storage device described in any one of the first to fifth embodiments; and a second electrode, which contains metal atoms that are ionized and move to the first electrode; during charging, a layer in which the metal atoms are precipitated is formed on the surface of the first electrode.

[0166] According to the secondary battery of the sixth embodiment, a high charging capacity can be obtained because a reaction of metal atoms being precipitated occurs at the negative electrode during charging.

[0167] [Seventh Form]

[0168] A method for manufacturing an electrode for a power storage device, comprising: (i) arranging a metal substrate having a plurality of protrusions composed of tiny metal particles on its surface in a reaction chamber; and (ii) supplying a raw gas containing at least a carbon-based gas to the reaction chamber to generate high-density plasma, and causing a carbon nanostructure composed of graphene extending elongatedly from the surface of the protrusion to grow to cover the entire surface of the protrusion, thereby forming the carbon nanostructure into a plurality of tiny granular bodies covering the entire surface layer, thereby forming an active material layer having a fine concave-convex structure on the surface of the granular bodies densely arranged on the metal substrate.

[0169] According to the seventh aspect of the manufacturing method, it is easy to form an active material layer having a plurality of granular carbon nanostructures formed so as to cover the entire surface layer on the surface of the metal substrate constituting the current collector.

[0170] [Eighth Form]

[0171] The manufacturing method of the seventh embodiment further comprises the step of preparing the metal substrate. In the step of preparing the metal substrate, the metal particles are precipitated on the flat surface of the base material of the metal substrate by electrolytic precipitation, thereby forming the protrusions.

[0172] According to the eighth aspect of the manufacturing method, the protrusions on the surface of the metal substrate can be easily formed by performing electrolytic deposition on the base material of the metal substrate.

[0173] [Ninth Form]

[0174] In the eighth aspect of the manufacturing method, the protrusions including a particle assembly in which the metal particles are densely aggregated can be formed on the flat surface of the base material of the metal substrate by the electrolytic deposition.

[0175] According to the ninth aspect of the manufacturing method, the formation of the granular body becomes easier due to the particle aggregate on the surface of the metal substrate.

[0176] [Tenth Form]

[0177] In the manufacturing method described in any one of the seventh to ninth aspects, when the carbon nanostructure is formed on the surface of the metal substrate in the reaction chamber, the metal substrate may be controlled to be at room temperature or above but less than 700°C.

[0178] According to the tenth aspect of the manufacturing method, the heating temperature for forming the carbon nanostructure can be lowered, so the manufacturing efficiency of the electrode for a power storage device can be further improved.

[0179] Description of Reference Numerals

[0180] 10 Secondary batteries

[0181] 11. Container

[0182] 12 Electrolyte

[0183] 15 Isolation

[0184] 16. First electrode chamber

[0185] 17. Second electrode chamber

[0186] 20 First electrode (electrode for power storage device)

[0187] 21 metal substrate

[0188] 21a First surface

[0189] 21b Second surface

[0190] 22 Active material layer

[0191] 23 Granular body

[0192] 25 Carbon Nanostructures

[0193] 26 Metal Particles

[0194] 27 Particle Structure

[0195] 28 protrusion

[0196] 29 Amorphous carbon layer

[0197] 30 Second electrode

[0198] 31. Positive electrode collector

[0199] 31a First surface

[0200] 31b Second surface

[0201] 32 Positive electrode active material layer

[0202] 50 Surface treatment device

[0203] 51 Delivery roller

[0204] 52 Guide roller

[0205] 53 Winding roller

[0206] 55 Electrolytic bath

[0207] 56 Electrolyte

[0208] 58 Electrode Plate

[0209] 60 Manufacturing Equipment

[0210] 61 Reaction Chamber

[0211] 62 Exhaust

[0212] 63 Exhaust pipe

[0213] 64 Vacuum Pump

[0214] 65 Raw gas supply unit

[0215] 66 Raw gas storage

[0216] 67 Flow Control Unit

[0217] 67a Gas delivery device

[0218] 67b Flow control valve

[0219] 68 Raw material introduction piping

[0220] 70 Board Support Department

[0221] 71 Heater

[0222] 72 Quartz cover

[0223] 73 Heater

[0224] 75 Upper electrode

[0225] 76 Power supply unit

[0226] 81 Vacuum gauge

[0227] 82 Thermocouple

[0228] BM substrate

[0229] CS Concave-convex structure

[0230] GS Graphene.

Claims

1. An electrode for a power storage device, comprising: 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 surface of the active material layer has a fine concavo-convex structure, and the fine concavo-convex structure is formed by densely arranging a plurality of tiny granular bodies; A carbon nanostructure is disposed over the entire surface layer of the granular body, and the carbon nanostructure is composed of graphene extending elongatedly outward from the granular body.

2. The electrode for a power storage device according to claim 1, in, A plurality of protrusions composed of tiny metal particles are formed on the surface of the metal substrate; The granular body is formed by arranging the carbon nanostructure extending from the surface of the metal particle so as to cover the entire surface of the protrusion.

3. The electrode for a power storage device according to claim 2, in, The protrusion includes a particle aggregate, and the particle aggregate is composed of a plurality of the metal particles densely aggregated.

4. The electrode for a power storage device according to claim 2 or 3, in, The projection area of ​​the protrusion along the thickness direction of the metal substrate is larger than 0.01 μm 2 And 10000μm 2 the following, The density of the projection area of ​​the protrusion when the metal substrate is projected along the thickness direction is 1 piece / mm 2 More than but less than 10 8 Pieces / mm 2 .

5. The electrode for a power storage device according to any one of claims 1 to 4, in, The average particle size of the granular body is not less than 0.1 μm and not more than 10.0 μm.

6. A secondary battery comprising: The first electrode is composed of the electrode for a power storage device according to any one of claims 1 to 5; and A second electrode comprising metal atoms that are ionized and moved to the first electrode; During charging, a layer in which the aforementioned metal atoms are precipitated is formed on the surface of the first electrode.

7. A method for producing an electrode for a power storage device, comprising: The step of placing a metal substrate having a plurality of protrusions composed of fine metal particles on the surface thereof in a reaction chamber; and A raw material gas containing at least a carbon-based gas is supplied to the reaction chamber to generate high-density plasma, and a carbon nanostructure composed of graphene extending elongatedly from the surface of the metal particle is grown to cover the entire surface of the protrusion, thereby forming a plurality of tiny granules arranged to cover the entire surface layer, thereby forming an active material layer having a fine concave-convex structure on the surface of which the granules are densely arranged, on the metal substrate.

8. The method for manufacturing an electrode for a storage device according to claim 7, comprising the step of preparing the metal substrate, wherein the metal particles are precipitated by electrolytic precipitation on a flat surface of a base material of the metal substrate, thereby forming the protrusions.

9. The method for producing an electrode for a power storage device according to claim 7 or 8, in, By the electrolytic deposition, the protrusions including a particle assembly in which the metal particles are densely aggregated are formed on the flat surface of the base material of the metal substrate.

10. The method for producing an electrode for a power storage device according to any one of claims 7 to 9, in, When the carbon nanostructure is formed on the surface of the metal substrate in the reaction chamber, the metal substrate is controlled to be at room temperature or higher but less than 700°C.

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