Secondary battery, secondary battery electrode, secondary battery manufacturing method, and secondary battery electrode manufacturing method

Abstract

A secondary battery is provided with: a container filled with an electrolyte solution; a separator having electrical insulating properties and ion conductivity and partitioning the internal space of the container into a first electrode chamber and a second electrode chamber; a first electrode formed of a metal substrate and housed in the first electrode chamber; and a second electrode which is housed in the second electrode chamber and contains metal atoms that are ionized and moved to the first electrode. The outer surface of the metal substrate has a fine concavo-convex structure comprising a plurality of protrusions comprising metal particles and having a maximum width of 0.5 [mu] m or more and 30.0 [mu] m or less; during charging, the metal atoms are deposited on the surfaces of the protrusions.

Description

Technical Field

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

[0002] As for one form of chargeable and dischargeable storage device, a secondary battery is known. Usually, in the electrode for a secondary battery, an active material layer is formed on the surface of the collector, and the active material layer is composed of a substance that participates in the battery reaction of the secondary battery. For example, in the lithium ion secondary battery disclosed in Japanese Patent No. 2668678 and Japanese Patent Publication No. 2010-9980 of the patent document, an active material layer containing lithium (Li) is provided at the positive electrode, and an active material layer composed of carbon (C) is provided at the negative electrode.

[0003] So far, in the technical field of secondary batteries, it is a general technical understanding that the active material layer of the electrode has a great influence on the battery performance. In order to improve the battery performance of secondary batteries, various active material layers have been continuously studied. As an example of the research results, for example, it has been found that in lithium-ion secondary batteries, when the active material layer of the negative electrode is composed of graphite as in Patent Document 1, the battery performance is further improved when the active material layer of the negative electrode is composed of carbon nanowalls as in Patent Document 2.

[0004] [Prior art literature]

[0005] [Patent Document]

[0006] Patent Document 1: Japanese Patent No. 2668678

[0007] Patent document 2: Japanese Patent Application Publication No. 2010-9980. Summary of the invention

[0008] [Problems to be solved by the invention]

[0009] However, as mentioned above, even if the active material layer of carbon nanowall is applied to lithium ion secondary batteries, its battery performance still cannot fully achieve the high battery performance required for secondary batteries. The same is true for secondary batteries other than lithium ion secondary batteries when other materials other than carbon nanowall are applied as active materials.

[0010] In addition, depending on the type of active material layer, it may be difficult to mass-produce electrodes for secondary batteries. For example, in the manufacturing process of lithium-ion secondary batteries, when the electrode with the active material layer of carbon nanowall is rolled into a roll for transportation and storage, the carbon nanowall may be damaged or fall off due to compression stress, shear stress, etc.

[0011] The above-mentioned problems are not limited to lithium ion secondary batteries but are common to various secondary batteries. An object of the present invention is to provide a secondary battery electrode which can achieve high battery performance and has a simple structure and is easy to manufacture, and a secondary battery having the secondary battery electrode.

[0012] [Methods used to solve the problem]

[0013] The inventor of the present invention has been continuously researching electrodes for power storage devices, and finally obtained a discovery that overturned the general technical understanding of the above-mentioned active material layer, and successfully developed a secondary battery electrode that has a simpler structure than before, is easy to manufacture, and can significantly improve battery performance. The present invention can be implemented in the following forms, for example.

[0014] One form of the present invention is provided as a secondary battery. This form of secondary battery comprises: a container filled with an electrolyte; a separator having electrical insulation and ion conductivity, which divides the internal space of the container into a first electrode chamber and a second electrode chamber; a first electrode, which is composed of a metal substrate and is accommodated in the first electrode chamber; and a second electrode, which is accommodated in the second electrode chamber and contains metal atoms that will ionize and move to the first electrode. The outer surface of the metal substrate has a fine concave-convex structure composed of a plurality of convex portions, the plurality of convex portions are composed of metal particles and the maximum width is greater than 0.5 μm and less than 30.0 μm; when charging, the metal atoms will precipitate on the surface of the convex portions.

[0015] The inventor of the present invention has found that if the first electrode is formed by forming a metal substrate with a concave-convex structure having convex portions of the above-mentioned size on the outer surface, even if there is no active material layer on the surface, the battery performance of the secondary battery can be further improved compared to the case where there is an active material layer. According to the secondary battery of this type, the charging capacity, battery performance, etc. can be improved by the novel structure of not setting an active material layer on the first electrode. In addition, according to the secondary battery of this type, since the active material layer can be set on the first electrode, the manufacturing steps of the secondary battery can be made easier accordingly.

[0016] The present invention can be implemented in various forms other than secondary batteries. For example, the present invention can be implemented in the form of an electrode for a secondary battery, a method for manufacturing a secondary battery, a method for manufacturing an electrode for a secondary battery, a manufacturing device for executing these manufacturing methods, etc. In addition, the present invention can be implemented in the form of a device, system, etc. driven by the power of a secondary battery, a power generation device equipped with a secondary battery, a power generation system, etc. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram showing the structure of a secondary battery.

[0018] Figure 2 This is a schematic cross-sectional view schematically showing a first embodiment of the protrusion of the metal substrate.

[0019] Figure 3 This is a schematic cross-sectional view schematically showing a second embodiment of the protrusion of the metal substrate.

[0020] Figure 4 is a step flow chart showing the manufacturing steps of a secondary battery.

[0021] Figure 5 This is a schematic diagram showing the structure of a surface treatment device.

[0022] Figure 6 It is an explanatory diagram showing a photographic image of the embodiment.

[0023] Figure 7 It is an explanatory diagram showing a photographic image of a comparative example.

[0024] Figure 8 It is an explanatory diagram showing the evaluation test results of the battery performance of the first embodiment.

[0025] Fig. 9 It is an explanatory diagram showing the evaluation test results of the battery performance of the second example.

[0026] Fig.10 It is an explanatory diagram showing the evaluation test results of the battery performance of the first comparative example.

[0027] Fig.11 It is an explanatory diagram showing the evaluation test results of the battery performance of the second comparative example.

[0028] Fig.12 It is an explanatory diagram showing the evaluation test results of the battery performance of the third comparative example.

[0029] Fig.13 It is an explanatory diagram showing the evaluation test results of the battery performance of Examples and Comparative Examples. DETAILED DESCRIPTION

[0030] Embodiments of a secondary battery, a secondary battery electrode, a method for producing a secondary battery, and a method for producing an electrode for a secondary battery according to the present invention will be described below with reference to the drawings.

[0031] 1. Implementation Method

[0032] 1-1. Composition of secondary batteries:

[0033] Figure 1 1 is a schematic diagram showing the structure of a secondary battery 10 of this embodiment. The secondary battery 10 of this embodiment is a lithium ion secondary battery in which lithium (Li) 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 1In the figure, the container 11 is appropriately illustrated by a dotted chain line, and the partition 15 is illustrated by a dotted line.

[0034] The container 11 has an internal space filled with an electrolyte 12. The container 11 is liquid-tightly constructed of a material that is not easily reactive with the electrolyte 12. The electrolyte 12 has the property of transferring 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 a solution formed by dissolving a lithium salt in an organic solvent, and can transfer lithium ions. As for the lithium salt of the electrolyte 12, for example, lithium hexafluorophosphate (LiPF6) can be used. In addition, as for the organic solvent, for example, dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), etc. can be used.

[0035] 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 is composed of a film-like member such as a resin film or non-woven fabric having a porous structure, and has electrical insulation and ion conductivity. The separator 15 electrically insulates the first electrode 20 from the second electrode 30 and allows metal ions transmitted via the electrolyte 12 to penetrate.

[0036] The first electrode 20 corresponds to the secondary battery electrode of this embodiment. In the following description, the first electrode 20 is also simply referred to as “electrode 20 .” In the secondary battery 10 of this embodiment, the electrode 20 constitutes a negative electrode. The electrode 20 is constituted by a metal substrate 21 .

[0037] In the present embodiment, the metal substrate 21 is made of a copper (Cu) metal foil. If it is Cu, it is easy to form the concave-convex structure described later on the outer surface and it is easy to improve the battery performance of the secondary battery 10. In addition, if it is Cu, it is easy to obtain and easy to process. The metal substrate 21 may also be made of a Cu alloy. Here, the metal substrate 21 may not be made of metal foil, for example, it may be made of a metal thin plate. The metal substrate 21 may not be formed in a flat plate shape, but may be bent into various shapes such as a cylindrical or wavy shape.

[0038] The metal substrate 21 functions as a current collector of the electrode 20. In a well-known secondary battery, an active material layer composed of a substance that participates in charging and discharging is usually provided on the surface of the current collector. In contrast, such an active material layer is not formed on the surface of the metal substrate 21 of the present embodiment. Instead, a fine concavo-convex structure 23 is formed on the outer surface of the metal substrate 21 of the present embodiment. The concavo-convex structure 23 is respectively provided on both sides of the first surface 21a and the second surface 21b of the metal substrate 21.

[0039] The concave-convex structure 23 includes a plurality of convex portions 24 having a maximum width Wmax of not less than 0.5 μm and not more than 30.0 μm. The convex portion 24 is a portion protruding along the thickness direction of the metal substrate 21. As described later, the convex portion 24 is composed of one or more metal particles. "Metal particles" refer to metal blocks having a particle-like shape. The metal particles are composed of the same type of metal as the metal constituting the metal substrate 21. When the metal substrate 21 is composed of an alloy, the metal particles are composed of the same type of metal as the metal of the main body of the alloy.

[0040] The maximum value Wmax of the width of the convex portion 24 corresponds to, for example, the maximum value of the widths of the convex portion 24 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. The direction “directly on the surface of the metal substrate 21” corresponds to the thickness direction of the metal substrate 21. “All directions” correspond to all directions perpendicular to the thickness direction of the metal substrate 21. These definitions are also the same in the following description.

[0041] The lower limit of the maximum value Wmax of the width of the convex portion 24 is preferably 0.6 μm or more, and more preferably 0.8 μm or more. The upper limit of the maximum value Wmax of the width of the convex portion 24 is preferably 28.0 μm or less, and more preferably 25.0 μm or less. Here, in addition to the convex portion 24 included in the numerical range of the maximum value Wmax of the width described above, the concavo-convex structure 23 may also include a convex portion having a width smaller than the lower limit of the numerical range of the maximum value Wmax of the width described above.

[0042] As described above, the metal substrate 21 does not form an active material layer, and each convex portion 24 of the concavo-convex structure 23 is directly immersed in the electrolyte 12 in the secondary battery 10 before charging. "Before charging" here refers to a state that has not been charged even once after manufacturing. As described later, when the secondary battery 10 is charged, metal atoms ionized and moved from the second electrode 30 will be precipitated on the surface of the convex portion 24 of the concavo-convex structure 23, and in this embodiment, Li will be precipitated.

[0043] The details of the structure of the protrusion 24 and the method of forming the concavo-convex structure 23 of the metal substrate 21 will be described later.

[0044] The second electrode 30 constitutes the positive electrode of 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 composed of, for example, a metal foil such as aluminum (Al) or titanium (Ti). The positive electrode collector 31 may also be composed 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, a wavy shape, etc.

[0045] 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 collector 31. The positive electrode active material layer 32 contains a conductive auxiliary agent, a binder, and a positive electrode active material containing Li atoms. The positive electrode active material layer 32 may also include a thickener. As for the positive electrode active material, for example, a ternary substance can be used, and lithium cobalt oxide (LiCoO2), lithium manganese oxide (LMO), lithium nickel oxide (NCA), etc. can also be used. 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.

[0046] Reference Figure 2 and Figure 3 An example of the structure of the convex portion 24 constituting the concavo-convex structure 23 included in the metal substrate 21 will be described. Figure 2 and Figure 3 This is a schematic cross-sectional view schematically showing a part of the cross-sectional structure of the metal substrate 21 in an arbitrary cross-section along the thickness direction.

[0047] Figure 2 and Figure 3 Examples of the types of the protrusions 24 having different shapes are shown in FIG. Figure 2 The protrusion 24 a is shown in the figure as a first example of the convex portion 24 . Figure 3 2 shows a first granular body 24b as a second type example of the projection 24 and a second granular body 24c as a third type example. The type examples of the projection 24 will be described below in order.

[0048] Reference Figure 2 The protrusion 24a of the first type example of the convex portion 24 is composed of a plurality of tiny metal particles 25 with a particle size Rp of 0.5 μm or more and 5.0 μm or less, which are densely stacked and aggregated. The protrusion 24a has a structure in which a plurality of tiny metal particles 25 are aggregated into a bead-like stack, and a concave-convex structure formed by densely arranged fine metal particles 25 is formed on the surface, and the whole has a structure protruding from the surrounding.

[0049] In this specification, "particle" refers to the concept of tiny blocks of various shapes, which is not necessarily limited to a roughly spherical shape, and also includes the concept of a shape with an irregular concave-convex structure on the surface. In addition, in this specification, "particle size" refers to the maximum value among the diameters of particles in all directions measured in multiple images taken directly on the metal substrate 21 by, for example, a scanning electron microscope.

[0050] In the protrusion 24a, the maximum width Wmax of the convex portion 24 corresponds to the maximum value of the distances between the ends of the plurality of metal particles 25 constituting the protrusion 24a in the direction perpendicular to the thickness direction of the metal substrate 21. The lower limit of the particle size Rp of each metal particle 25 constituting the protrusion 24a is preferably 0.6 μm or more, more preferably 0.8 μm or more. In addition, the upper limit of the particle size Rp of the metal particle 25 is preferably 4.0 μm or less, more preferably 3.0 μm or less.

[0051] The protrusion 24a has a height Hp of 1.0 μm or more and 15.0 μm or less. The height Hp of the protrusion 24a corresponds to the distance in the thickness direction of the metal substrate 21 between the lowermost end and the uppermost end of the protrusion 24a measured in a photographic image taken from a direction perpendicular to the thickness direction of the metal substrate 21 by a scanning electron microscope, for example. The lower limit of the height Hp of the protrusion 24a is preferably 2.0 μm or more, more preferably 4.0 μm or more. The upper limit of the height Hp of the protrusion 24a may be 12.0 μm or less, or 10.0 μm or less.

[0052] Reference Figure 3 The first granular body 24b of the second type example of the convex portion 24 and the second granular body 24c of the third type example are commonly composed of metal particles 25 regarded as a single body, but have different sizes and shapes. The first granular body 24a and the second granular body 24b are different in height. The height of the granular bodies 24b and 24c is equivalent to the distance in the thickness direction of the metal substrate 21 between the lower end and the upper end of the granular bodies 24b and 24c measured in a photographic image taken from a direction perpendicular to the thickness direction of the metal substrate 21 by a scanning electron microscope, for example.

[0053] The particle size Rq of the first granular body 24b is greater than or equal to 0.5 μm and less than or equal to 5.0 μm, and its height Hq is approximately less than or equal to its particle size Rq. For the first granular body 24b, its particle size Rq is equivalent to the maximum width Wmax of the convex portion 24. The lower limit of the particle size Rq of the first granular body 24b is preferably greater than or equal to 0.6 μm, and more preferably greater than or equal to 0.8 μm. The upper limit of the particle size Rq of the first granular body 24b may be less than or equal to 4.5 μm, or less than or equal to 4.0 μm.

[0054] The second granular body 24c has a longitudinal shape. The particle size Rr of the second granular body 24c is greater than 0.5 μm and less than 8.0 μm, and the second granular body 24c has a height Hr greater than its particle size Rr. The particle size Rr of the second granular body 24c is equivalent to the maximum value Wmax of the width of the convex portion 24. The lower limit of the particle size of the second granular body 24c is preferably greater than 0.6 μm, and more preferably greater than 0.8 μm. The upper limit of the particle size of the second granular body 24c can be less than 7.0 μm, and can also be less than 5.0 μm.

[0055] The height Hr of the second granular body 24c may be, for example, 1.0 μm or more and 12.0 μm or less. The lower limit of the height Hr of the second granular body 24c may be 2.0 μm or more, or 3.0 μm or more. In addition, the upper limit of the height Hr of the second granular body 24c may be 10.0 μm or less, or 8.0 μm or less.

[0056] The concavo-convex structure 23 may have, for example, a structure in which protrusions 24a are densely arranged on the surface of the metal substrate 21. The concavo-convex structure 23 may also have a structure in which first granules 24b, second granules 24c, etc. are arranged between the protrusions 24a. The concavo-convex structure 23 may also have a structure in which the first granules 24b or the second granules 24c are distributed over the entire surface of the metal substrate 21. The concavo-convex structure 23 may also have a structure in which protrusions 24a, second granules 24c, etc. are arranged between the first granules 24b arranged over the entire surface of the metal substrate 21. The concavo-convex structure 23 may also have a structure in which protrusions 24a, first granules 24b, and second granules 24c are mixed. The concavo-convex structure 23 may also have a structure in which, in addition to the protrusions 24, particle-shaped protrusions smaller than the first granules 24b and the second granules 24c are included.

[0057] The projection area of ​​the convex portion 24 including the protrusion 24a, the granular bodies 24b, 24c, etc., projected 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 convex portion 24 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 24 of such a size can be easily formed by surface treatment of the base material of the metal substrate 21 by electrolytic deposition.

[0058] 1-2. Battery reaction of secondary battery:

[0059] The chemical reaction during the charge and discharge of the secondary battery 10 can be represented by the following reaction formula, for example. When the positive electrode material is LiCoO2, the reaction formula of the second electrode 30 which is the positive electrode can be represented by the following formula (1). x represents the ratio of the atoms in the reaction, which is a real number greater than 0 but less than 1.

[0060]

[0061] On the other hand, the reaction formula of the electrode 20 which is the negative electrode can be expressed by the following formula (2). As shown in formula (2), when the secondary battery 10 is charged, Li is deposited on the surface of the protrusion 24 of the electrode 20 .

[0062]

[0063] As shown in the above formula (2), according to the secondary battery 10 of this embodiment, theoretically, as long as Li can be deposited in the electrode 20, charging can be performed and a high charging capacity can be obtained.

[0064] Here, the inventors of the present invention have found that if a concavo-convex structure 23 having convex portions 24 of the above-mentioned size is formed on the outer surface of the metal substrate 21 constituting the electrode 20, the precipitation of Li on the surface of the metal substrate 21 can be promoted. Thus, when considering based on the observation based on the nucleation theory, the reason for promoting the precipitation of Li can be inferred that Li is easily precipitated from the convex portions 24 of the concavo-convex structure 23 as the starting point.

[0065] Thus, according to the secondary battery 10 of this embodiment, even if there is no active material layer in the electrode 20, the presence of the convex portion 24 of the concavo-convex structure 23 of the metal substrate 21 promotes the precipitation of Li on the surface of the metal substrate 21, so that the battery performance such as the charging capacity and the specific capacity can be improved. In addition, according to the secondary battery 10 of this embodiment, the active material layer on the surface of the electrode 20 can be omitted, and the structure of the secondary battery 10 can be simplified, and the materials used in the manufacture of the secondary battery 10 can be reduced.

[0066] In addition, according to the secondary battery 10 of this embodiment, the convex portions 24 of the concavo-convex structure 23 are uniformly distributed on the surface of the metal substrate 21, so that Li can be uniformly deposited on the surface of the metal substrate 21. Accordingly, the formation of dendrites in the electrode 20 can be suppressed, and damage and degradation of the secondary battery 10 caused by dendrites can be suppressed.

[0067] Here, for example, in the manufacturing process of a well-known secondary battery having an active material layer of a carbon nanowall, when the electrode having the active material layer is rolled into a roll for transportation, storage, etc., a portion of the carbon nanowall may be damaged or fall off. In contrast, according to the electrode 20 of this embodiment, in the manufacturing process of the secondary battery 10, even if it is rolled into a roll for transportation, storage, etc., such degradation or falling of the active material layer will not occur. Accordingly, according to the electrode 20 of this embodiment, it is easy to handle, so the mass production of the electrode 20 becomes easy.

[0068] 1-3. Method for manufacturing secondary battery:

[0069] Figure 4 1 is a flowchart showing the steps of manufacturing the secondary battery 10. Steps P1 and P2 are steps of manufacturing the electrode 20.

[0070] In step P1, a base material BM of the metal substrate 21 is prepared. The base material BM is, for example, a metal foil, a metal thin plate, etc., and has a flat surface. In this embodiment, the base material BM is a copper foil. In step P2, the base material BM is surface treated by electrolytic deposition, thereby forming the above-mentioned concavo-convex structure 23 on both sides.

[0071] Figure 5 : is a schematic diagram showing the structure of the surface treatment device 50 used in step P2. 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.

[0072] 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.

[0073] The electrolyte 56 in the electrolytic bath 55 is a solution that can dissolve metal atoms of the same type as the metal constituting the substrate BM, and sulfuric acid (H2SO4) can be used, for example. The electrolyte 56 can have a concentration of, for example, about 0.5 to 2.0 M (volume molar concentration mol / L).

[0074] 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. The distance between the electrode plate 58 and the substrate BM can be, for example, about 2.0 to 6.0 cm.

[0075] During the conveyance 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, so that current flows. The applied voltage may be, for example, about 0.5 to 2.0 V. The current may be, for example, about 80.0 to 200.0 mA, and the current density may be 15.0 to 30.0 mA / cm 2In addition, the ambient temperature may be room temperature or a temperature in the range of 10 to 30° C. The processing 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 may be appropriately adjusted so that the convex portion 24 of the above-mentioned size can be formed.

[0076] In the electrolytic deposition in the surface treatment device 50, 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. The convex portions 24 are formed continuously on the surface of the substrate BM by the precipitated Cu particles. The convex portions 24 are formed so as to be distributed over the entire surface of the substrate BM.

[0077] 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 multi-stage structure for conveying the substrate BM to be repeatedly immersed in the electrolyte 56 of each electrolytic bath 55. At this time, the processing conditions such as the type, concentration, energization voltage, and conveying speed of the substrate BM of the electrolyte 56 in each electrolytic bath 55 may also be appropriately adjusted so that the convex portion 24 of the above-mentioned size can be formed.

[0078] The surface treatment of step P2 is preferably performed on both sides of the substrate BM. In the surface treatment device 50, a winding roller 53 on which the substrate BM with one side surface treated is wound is set as a delivery roller 51, and the substrate BM is transported to the electrolytic bath 55 again, thereby performing the surface treatment on the other side. In this way, the metal substrate 21 having fine concavo-convex structures 23 on both sides is completed.

[0079] Reference Figure 4 In the subsequent step P3, a second electrode 30 serving as a positive electrode is manufactured. In step P4, as Figure 1 As shown, the first electrode 20 and the second electrode 30 are assembled in the container 11 filled with the electrolyte 12. The metal substrate 21 constituting the first electrode 20 is accommodated in the container 11 in a state where the convex portions 24 of the concavo-convex structure 23 are directly immersed in the electrolyte 12. The secondary battery 10 is completed through the above steps.

[0080] In summary, according to the manufacturing steps of the secondary battery 10 of this embodiment, the metal substrate 21 having the concave-convex structure 23 on both sides can be efficiently manufactured by surface treatment through electrolytic deposition. In addition, since the metal substrate 21 is not provided with an active material layer, the number of steps can be reduced accordingly, and the manufacturing cost of the secondary battery 10 can be reduced.

[0081] As described above, even if the electrode 20 prepared in steps P1 and P2 is rolled into a roll for transportation, the active material layer will not be damaged or fall off, so it is easy to handle. Therefore, the mass production of the electrode 20 can be improved, and the manufacture of the secondary battery 10 using the electrode 20 becomes easy.

[0082] [Example]

[0083] Reference Figure 6 and Figure 7 Examples E1 and E2 of the electrode 20 according to the present embodiment and comparative examples C1, C2, and C3 thereof will be described.

[0084] Figure 8 Parts (a) and (b) of FIG. 1 show photographic images of the concavo-convex structure 23 of the metal substrate 21 of Example E1. Figure 8 Parts (c) and (d) respectively show photographic images of the surface of the concavo-convex structure 23 of Example E2. Figure 8 Part (a) and Figure 8 Part (c) is an image of the protrusion 24 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 Figure 8 Part (d) 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 Figure 8 The image of the portion (d) corresponds to an image of a projection region where the projection 24 is projected in the thickness direction of the metal substrate 21 .

[0085] The metal substrate 21 of Examples E1 and E2 uses copper foil as a substrate and is manufactured by performing the above-mentioned surface treatment by electrolytic deposition. In the electrolytic deposition of Example E2, a 1.5M H2SO4 solution is used as an electrolyte, a DC voltage of 1.0V is applied to the substrate in the electrolyte, and a current of 128ma flows. The distance between the substrate and the electrode is 3.5cm. This electrolytic deposition is performed at room temperature. The conveying speed of the substrate in the electrolyte is appropriately adjusted according to the target size of the protrusion 24 based on the previous experimental results.

[0086] like Figure 8As shown in parts (a) and (b), the concavo-convex structure 23 of Example E1 has a plurality of protrusions 24a formed by densely agglomerated metal particles 25 as protrusions 24. In Example E1, the plurality of protrusions 24a are distributed adjacent to each other and cover the entire surface of the metal substrate 21. The maximum value Wmax of the width of each protrusion 24a is approximately in the range of 1.0 to 30.0 μm. The height Hp of each protrusion 24a is approximately in the range of 1.0 to 15.0 μm. The particle size Rp of the metal particles 25 constituting the protrusion 24a is approximately in the range of 0.5 to 5.0 μm.

[0087] like Figure 8 As shown in parts (c) and (d) of the embodiment E2, the concavo-convex structure 23 has first granular bodies 24b and second granular bodies 24c as the convex parts 24. In the embodiment E2, the first granular bodies 24b distributed over the entire surface of the metal substrate 21 are mixed with the second granular bodies 24c.

[0088] The particle diameter Rq of the first granular body 24b is generally within the range of 0.5 to 5.0 μm. The height Hq of the first granular body 24b is generally within the range of 0.1 to 5.0 μm.

[0089] The particle diameter Rr of the second granular body 24c is generally within the range of 0.5 to 8.0 μm. The height Hr of the second granular body 24c is generally within the range of 1.0 to 15.0 μm. The second granular body 24c includes a plurality of granular bodies having a vertically elongated ellipsoidal shape.

[0090] The projection area of ​​the projection of the convex portion 24 in either embodiment E1 or E2 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 convex portion 24 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 within the range.

[0091] Figure 7 Parts (a) and (b) of FIG. 1 show photographic images of the surface of the metal substrate constituting the electrode of Comparative Example C1. Figure 7 Part (a) is an image obtained by photographing the surface of the metal substrate of Comparative Example C1 using a scanning electron microscope. Figure 7 Part (b) is higher than Figure 7 The image is captured at a magnification of the photographic image of part (a).

[0092] The electrode of Comparative Example C1 does not have an active material layer like Examples E1 and E2, but is composed of a metal substrate that constitutes a current collector. The metal substrate of Comparative Example C1 has substantially the same structure as the metal substrates of Examples E1 and E2, except that the surface treatment of electrolytic deposition as in Examples E1 and E2 is not performed. Figure 7 As shown in the images of parts (a) and (b), the metal substrate of Comparative Example C1 has a flat surface with almost no irregularities.

[0093] Figure 7 Part (c) shows a photographic image of the electrode of Comparative Example C2. Figure 7 Part (c) is an image taken with a scanning electron microscope directly on the surface of the active material layer of Comparative Example C2. The electrode of Comparative Example C2 has a structure in which a graphite active material layer is provided on the surface of a metal substrate having a flat surface similar to Comparative Example C1. Figure 7 Part (c) shows graphite particles constituting the active material layer.

[0094] Figure 7 Parts (d) and (e) show photographic images of the electrode of Comparative Example C3. Figure 7 Part (d) is an image of the surface layer of the electrode of Comparative Example C1, taken from a direction perpendicular to the thickness direction of the electrode using a scanning electron microscope. Figure 7 Part (e) is an image obtained by photographing the surface of the electrode of Comparative Example C1 using a scanning electron microscope.

[0095] The electrode of Comparative Example C3 has a structure in which a carbon nanowall is provided as an active material layer on the surface of a metal substrate having a flat surface similar to that of Comparative Example C1. Figure 7 The wrinkled white image in the image of part (d) and Figure 7 The mesh-like white streak-like image in the image of part (e) is a carbon nanowall. The carbon nanowall is formed in an irregular mesh shape with a substantially uniform height of about 1.0 μm over the entire surface of the metal substrate by CVD.

[0096] Figures 8 to 13 An explanatory diagram showing the results of a test for evaluating the battery performance of secondary batteries using the electrodes of Examples E1 and E2 and Comparative Examples C1, C2, and C3 as negative electrodes. Figure 8 and Fig. 9 The graphs obtained by using the secondary batteries of the electrodes of Examples E1 and E2 are shown in FIG. Fig.10 , Fig.11 ,and Fig.12 Graphs obtained from secondary batteries using electrodes of Comparative Examples C1, C2, and C3 are shown respectively. Figures 8 to 12In 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.13 The charge capacity and specific capacity of the secondary batteries using Example E1 and Comparative Examples C2 and C3 are shown in bar graphs, respectively. In this evaluation test, both the charge current and the discharge current were set to 0.5 mA.

[0097] The secondary batteries used in Examples E1 and E2 and Comparative Examples C1, C2, and C3 were lithium ion secondary batteries, and were produced in the configurations shown in Table 1 below.

[0098] Table 1

[0099]

[0100] like Fig.10 As shown, the secondary battery using the electrode composed of the metal substrate with a flat surface of Comparative Example C1 as the negative electrode cannot be charged or discharged. From this result, it can be seen that the metal substrate without a concavo-convex structure on the outer surface cannot function as an electrode of a secondary battery.

[0101] like Fig.11 and Fig.13 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, Fig.12 and Fig.13 As shown, the secondary battery of Comparative Example C3 using an active material layer having the same thickness of carbon nanowall has a charge capacity of 12.6 [mAh] and a specific capacity of 9.4 [mAh / cm 2 ].

[0102] From the results of Comparative Examples C1, C2, and C3, it can be seen that by providing an active material layer on a flat metal substrate, the function of an electrode of a secondary battery can be exerted. In addition, it can be seen that applying carbon nanowalls to the active material layer of the negative electrode can significantly improve the battery performance of the secondary battery compared to the case where graphite is applied to the active material layer.

[0103] However, if Figure 8 and Fig. 9 As shown in FIG. 1 , the charging capacity of the secondary batteries of Examples E1 and E2 is approximately 14.0 [mAh]. Fig.13 As shown, the specific capacity of the secondary battery using Example E1 is 10.5 [mAh / cm 2 ]. Fig.13 Although not shown in the figure, the secondary battery of Example E2 also achieved the same specific capacity.

[0104] Thus, compared to the secondary batteries of Comparative Examples C2 and C3 using active material layers, the battery performance of any of Examples E1 and E2 is clearly significantly improved. The cause of this result can be inferred that the convex portion 24 of the concave-convex structure 23 formed on the metal substrate 21 of Examples E1 and E2 promotes the precipitation of Li more than the active material layer. This result can be said to subvert the well-known general view that an active material layer is required for electrodes for secondary batteries, and this result can be said to be a new discovery that the absence of an active material layer can improve battery performance, which cannot be easily thought of from the well-known technical common sense.

[0105] In summary, the secondary battery electrode and the secondary battery using the secondary battery electrode according to the present invention can significantly improve the battery performance of the secondary battery. In addition, the secondary battery electrode according to the present invention has a simple structure without an active material layer, so the manufacture of the secondary battery electrode and the manufacture of the secondary battery becomes easy.

[0106] 2. Other implementation methods

[0107] The present invention is not limited to the configurations of the above-mentioned embodiments or examples, and can also be implemented by, for example, the following forms. The configurations described below in other embodiments are all considered as one form example for implementing the present invention in the same manner as the above-mentioned embodiments, the configurations described in other embodiments in the above-mentioned embodiments, and examples.

[0108] 2-1. Other implementation methods 1:

[0109] The metal substrate 21 of the above embodiment may be made of a metal other than Cu. The metal substrate 21 may be made of, for example, any one of Cu alloy, Al, and Al alloy.

[0110] 2-2. Other implementation methods 2:

[0111] 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.

[0112] 2-3. Other implementation methods 3:

[0113] The convex portion 24 of the concavo-convex structure 23 may have a structure different from the protrusion 24a, the granular bodies 24b, 24c, etc. The convex portion 24 of the concavo-convex structure 23 may be configured in a shape such as a substantially semicircular shape or a substantially conical shape.

[0114] 2-4. Other implementation methods 4:

[0115] In step P2 of the method for manufacturing the secondary battery 10 described in the above embodiment, the concavo-convex structure 23 may be formed on the base material BM of the metal substrate 21 by a method other than electrolytic deposition. The concavo-convex structure 23 of the metal substrate 21 may also be formed by, for example, surface treatment by CVD, oxidation treatment of the metal substrate, etc.

[0116] 3. Type Example

[0117] The present invention can be implemented in the following aspects.

[0118] [First Form]

[0119] The first type provides a secondary battery. The first type of secondary battery comprises: a container filled with an electrolyte; a separator having electrical insulation and ion conductivity, dividing the internal space of the container into a first electrode chamber and a second electrode chamber; a first electrode composed of a metal substrate and housed in the first electrode chamber; and a second electrode housed in the second electrode chamber, comprising metal atoms that are ionized and move to the first electrode; the outer surface of the metal substrate has a fine concave-convex structure composed of a plurality of convex portions, the plurality of convex portions are composed of metal particles and the maximum width is greater than 0.5 μm and less than 30.0 μm; during charging, the metal atoms are precipitated on the surface of the convex portions.

[0120] According to the first type of secondary battery, the charging capacity and battery performance can be improved by providing a novel and simple structure in which a concave-convex structure including convex portions composed of metal particles is provided on a metal substrate and an active material layer is not provided on the first electrode. In addition, according to the first type of secondary battery, since an active material layer is not provided on the first electrode, the manufacturing steps of the secondary battery can be simplified accordingly and the manufacturing cost of the secondary battery can be reduced.

[0121] [Second Form]

[0122] In the secondary battery of the first type, the convex portion may include a protrusion, and the protrusion is formed by densely agglomerating a plurality of metal particles having a particle size of 0.5 μm or more and 5.0 μm or less.

[0123] According to the secondary battery of the second embodiment, the convex portion can be easily formed by a protrusion formed by dense aggregation of fine metal particles, thereby improving the battery performance.

[0124] [Third Form]

[0125] In the above-mentioned second type of secondary battery, the above-mentioned protrusion may have a height of not less than 1.0 μm and not more than 15.0 μm.

[0126] According to the third type of secondary battery, the protrusions can further promote the precipitation of metal atoms that participate in the battery reaction at the first electrode, so the battery performance can be further improved.

[0127] [Fourth Form]

[0128] In the secondary battery described in any one of the first to third aspects, the protrusions may include longitudinally elongated particles having a particle size of 0.5 μm to 5.0 μm and a height greater than the particle size.

[0129] According to the secondary battery of the fourth embodiment, the battery performance can be further improved by having the granular body constituting the protrusions.

[0130] [Fifth Form]

[0131] In the secondary battery described in any one of the first to fourth aspects, the projection area of ​​the convex portion 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 convex portion 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 .

[0132] According to the fifth type of secondary battery, since a plurality of protrusions can be present on the electrode surface, the battery performance can be further improved.

[0133] [Sixth Form]

[0134] In the secondary battery described in any one of the first to fifth aspects, the metal substrate may be made of copper or a copper alloy.

[0135] According to the sixth type of secondary battery, the concave-convex structure can be easily formed on the outer surface of the metal substrate, which can easily improve the battery performance.

[0136] [Seventh Form]

[0137] A seventh aspect provides a metal substrate for use as an electrode of a secondary battery. The metal substrate of the seventh aspect has a fine concave-convex structure consisting of a plurality of convex portions, the plurality of convex portions being composed of metal particles and having a maximum width of 0.5 μm or more and 30.0 μm or less; the metal substrate is contained in a container of the secondary battery filled with an electrolyte in a state where the convex portions are directly immersed in the electrolyte.

[0138] According to the seventh embodiment, the metal substrate can be used as a secondary battery electrode having no active material layer provided on the outer surface, and a secondary battery with high battery performance can be realized.

[0139] [Eighth Form]

[0140] The eighth aspect provides a method for manufacturing a secondary battery. The eighth aspect of the manufacturing method comprises: forming a fine concavo-convex structure on the surface of a metal substrate, the fine concavo-convex structure having a plurality of convex portions with a maximum width of 0.5 μm or more and 30.0 μm or less formed by metal particles; and assembling the metal substrate as an electrode of the secondary battery in a container filled with an electrolyte, and immersing the convex portions in the electrolyte.

[0141] According to the eighth aspect of the manufacturing method, a secondary battery having high battery performance can be obtained through a simple manufacturing process that does not include a step of providing an active material layer on the outer surface of the metal substrate.

[0142] [Ninth Form]

[0143] In the eighth aspect of the manufacturing method, the step of forming the concavo-convex structure may include the step of depositing metal particles on the outer surface of the metal substrate by electrolytic deposition to form the convex portions.

[0144] According to the manufacturing method of the ninth aspect, it is easy to form a concave-convex structure that helps the charge and discharge of the secondary battery on both sides of the metal substrate, thereby making it easier to manufacture a secondary battery with high battery performance.

[0145] [Tenth Form]

[0146] The tenth type of manufacturing method for an electrode for a secondary battery comprises: a step of preparing a substrate of a metal substrate constituting the aforementioned electrode; and a step of immersing the aforementioned substrate in an electrolyte in an electrolytic bath, and forming a fine concave-convex structure on the aforementioned substrate by electrolysis, wherein the fine concave-convex structure is configured with a plurality of convex portions with a maximum width of 0.5 μm or more and 30.0 μm or less, which are composed of metal particles; the aforementioned metal substrate is housed in the container of the aforementioned secondary battery in a state where the aforementioned convex portions are directly immersed in the aforementioned electrolyte.

[0147] According to the tenth embodiment of the manufacturing method, a concavo-convex structure that helps charge and discharge of the secondary battery can be easily formed on the outer surface of the metal substrate.

[0148] Description of Reference Numerals

[0149] 10 Secondary batteries

[0150] 11 Container

[0151] 12 Electrolyte

[0152] 15 Isolation

[0153] 16. First electrode chamber

[0154] 17. Second electrode chamber

[0155] 20 electrode (first electrode)

[0156] 21 metal substrate

[0157] 21a First surface

[0158] 21b Second surface

[0159] 23 Concave and convex structure

[0160] 24 convex part

[0161] 24a Protrusion

[0162] 24b First granule

[0163] 24c Second granule

[0164] 25 Metal Particles

[0165] 30 Second electrode

[0166] 31. Positive electrode collector

[0167] 32 Positive electrode active material layer

[0168] 50 Surface treatment device

[0169] 51 Delivery roller

[0170] 52 Guide roller

[0171] 53 Winding roller

[0172] 55 Electrolytic bath

[0173] 56 Electrolyte

[0174] 58 Electrode Plate

[0175] BM substrate.

Claims

1. A secondary battery comprising: a container filled with electrolyte; A separator having electrical insulation and ion conductivity, and dividing the internal space of the container into a first electrode chamber and a second electrode chamber; A first electrode, formed of a metal substrate and housed in the first electrode chamber; and A second electrode, housed in the second electrode chamber, comprising metal atoms that are ionized and move to the first electrode; The outer surface of the metal substrate has a fine concavo-convex structure composed of a plurality of convex portions, the plurality of convex portions are composed of metal particles and the maximum width thereof is not less than 0.5 μm and not more than 30.0 μm; During charging, the metal atoms are deposited on the surface of the protrusions.

2. The secondary battery according to claim 1, wherein The convex portion includes a protrusion, and the protrusion is composed of a plurality of metal particles having a particle size of 0.5 μm or more and 5.0 μm or less densely aggregated.

3. The secondary battery according to claim 2, wherein: The protrusion has a height of not less than 1.0 μm and not more than 15.0 μm.

4. The secondary battery according to any one of claims 1 to 3, wherein The convex portion includes a longitudinally long granular body having a particle size of 0.5 μm or more and 5.0 μm or less and a height greater than the particle size.

5. The secondary battery according to any one of claims 1 to 4, wherein The projection area of ​​the convex portion 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 convex portion 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 .

6. The secondary battery according to any one of claims 1 to 5, wherein The metal substrate is made of copper or a copper alloy.

7. A metal substrate for use as an electrode of a secondary battery, the metal substrate having a fine concavo-convex structure consisting of a plurality of convex portions, the plurality of convex portions being composed of metal particles and having a maximum width of 0.5 μm or more and 30.0 μm or less; The metal substrate is housed in a container of the secondary battery filled with an electrolyte solution in a state where the protrusions are directly immersed in the electrolyte solution.

8. A method for manufacturing a secondary battery, comprising: The step of forming a fine concavo-convex structure on the outer surface of the metal substrate, wherein the fine concavo-convex structure is provided with a plurality of convex portions having a maximum width of 0.5 μm or more and 30.0 μm or less, which are formed of metal particles; and The step of assembling the metal substrate as an electrode of the secondary battery in a container filled with an electrolyte solution and immersing the protrusions in the electrolyte solution.

9. The method for manufacturing a secondary battery according to claim 8, wherein: The step of forming the concavo-convex structure includes the step of depositing metal particles on the outer surface of the metal substrate by electrolytic deposition to form the convex portions.

10. A method for manufacturing an electrode for a secondary battery, comprising: A step of preparing a base material of a metal substrate constituting the aforementioned electrode; and The step of immersing the substrate in an electrolyte of an electrolytic bath to form a fine concavo-convex structure on the substrate by electrolysis, wherein the fine concavo-convex structure is provided with a plurality of convex portions having a maximum width of 0.5 μm or more and 30.0 μm or less, which are formed by metal particles; The metal substrate is housed in the container of the secondary battery in a state where the protrusions are directly immersed in the electrolyte.

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