Active material, method for producing active material, positive electrode, and secondary battery

Abstract

To provide an active material, capable of enlarging an interface with an electrolyte, for allowing ions to easily move to the electrolyte, a manufacturing method of the same, an electrode using the same, and a battery.SOLUTION: An active material has protrusions precipitated in a plurality of directions.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to an active material, a method for producing an active material, an electrode, and a battery. [Background technology]

[0002] In general, a secondary battery is composed of electrodes (positive and negative electrodes) and an electrolyte, and is charged and discharged by the movement of ions between the electrodes via the electrolyte. Such secondary batteries are used in a wide range of applications, from small devices such as mobile phones to large devices such as electric vehicles. Therefore, there is a demand for further improvement in the performance of secondary batteries. In particular, there is a demand for enlarging the interface between the active material in the electrodes and the electrolyte in order to facilitate the movement of ions between the electrodes via the electrolyte. Here, the active material refers to a substance involved in a reaction that generates electricity.

[0003] Lithium cobalt oxide (LiCoO) as the active material in the positive electrode 2 In order to increase the interface between the lithium ion battery and the electrolyte and improve the charge-discharge efficiency, LiCoO was crystallized by the flux method. 2 (See Non-Patent Document 1.) It is also described that when the charge / discharge rate of a sample structure using lithium as the active material in the electrode and a solid electrolyte as the electrolyte is increased, needle-shaped active material is precipitated from the solid electrolyte (See Non-Patent Document 2.) [Prior art documents] [Non-patent literature]

[0004] [Non-Patent Document 1] Journal of Materials Chemistry A,2013,00,1-3,p.1-6 [Non-Patent Document 2] "Special feature: Functionalization of powders and development of new materials through nanotechnology", Toyota Central R&D Labs., pp.21-24 Summary of the Invention [Problem to be solved by the invention]

[0005] LiCoO crystallized by the flux method described in Non-Patent Document 1 2 As an active material in the positive electrode, the study was carried out. As a result, it was found that although ions moved to the electrolyte because the electrode resistance, which is an index showing the ease of ion movement to the electrolyte, was relatively small, there was room for further improvement. In addition, even when the sample structure in which needle-shaped active material was precipitated from the solid electrolyte described in Non-Patent Document 2 was used, the electrode resistance was not sufficiently small, so that ions did not easily move to the electrolyte.

[0006] Therefore, an object of the present invention is to provide an active material that can enlarge the interface with an electrolyte and facilitate the transfer of ions to the electrolyte, and a method for producing the active material. Another object of the present invention is to provide an electrode and a battery using the active material. [Means for solving the problem]

[0007] An active material according to one aspect of the present invention is an active material that is applied to a secondary battery together with a electrolyte, the active material including a core portion and a plurality of layer-like gap portions disposed outside the core portion. of layer state A particle portion having a shell portion and protrusions protruding in multiple directions from the shell portion. output The present invention is characterized by having a part.

[0010] The method for producing an active material according to one aspect of the present invention is applied to a secondary battery together with an electrolyte, and protrusions precipitated in multiple directions are formed. output A method for producing an active material having a part, A first step of forming a material layer by arranging particulate lithium cobalt oxide having a softening point temperature higher than the thermal decomposition temperature of the resin substrate on a resin substrate, a second step of laminating a plurality of the material layers to form a laminate, and a second step of firing the laminate at a temperature higher than the thermal decomposition temperature in an atmosphere containing oxygen gas to sinter the lithium cobalt oxide, thereby forming protrusions in a plurality of directions from the particulate lithium cobalt oxide. output The method has a third step of precipitating a part. [Effect of the Invention]

[0011] According to the present invention, it is possible to provide an active material capable of increasing the interface with an electrolyte and facilitating the movement of ions into the electrolyte, a method for manufacturing the active material, an electrode using the active material, and a battery. [Brief Description of the Drawings]

[0012]

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Mode for Carrying Out the Invention

[0013] As a result of the study by the present inventors, it was found that in order to increase the interface between the active material and the electrolyte, it is important to increase the surface area of the active material. Therefore, an active material having protrusions deposited in a plurality of directions was used. As a result, it is considered that the surface area of the active material increases and the interface with the electrolyte increases, and ions move easily from the active material to the electrolyte. In the present invention, the increase in the interface with the electrolyte and the ease of ion movement from the active material to the electrolyte are evaluated using the index of "electrode resistance" for convenience.

[0014] <Active material> Protrusions deposited from the particle portion of the active material may include needle-like, dendritic that protrude like trees, pleated that protrude like a curtain, etc., and may be paraphrased as protrusions protruding from the particle portion. Examples of the active material include a positive electrode active material and a negative electrode active material. Among them, the active material is preferably a positive electrode active material. The positive electrode active material preferably contains an oxide having Li, and the oxide having Li preferably further contains Co. The positive electrode active material preferably contains lithium cobaltate (LiCoO 2 ).

[0015] In addition, the protrusions deposited in a plurality of directions preferably contain an oxide having Li, and the oxide having Li preferably further contains Co. Thus, it is preferable that the protrusions and the portions other than the protrusions in the active material contain the same material.

[0016] <Method for manufacturing active material> Hereinafter, with reference to the drawings, an example of the method for manufacturing the active material will be described in detail. Hereinafter, the case where a positive electrode active material is used as the active material will be described as an example, but the method for manufacturing the active material described below can also be used when a negative electrode active material is used.

[0017] The method for manufacturing the positive electrode active material of the present invention has the following three steps (the first step, the second step, and the third step). (1) First step (S101 in FIG. 1) of forming a material layer in which a positive electrode active material is disposed on a substrate (2) Second step (S102 in FIG. 1) of forming a laminate by laminating a plurality of material layers (3) Third step (S103 in FIG. 1) of sintering the laminate to manufacture a positive electrode active material

[0018] (First step) The first step is a step of forming a material layer in which a positive electrode active material is disposed on a substrate. In the first step, a material layer is formed on the substrate using a material layer forming apparatus. Hereinafter, the material layer forming apparatus will be described in order with respect to the material layer forming apparatus 1 and the material layer forming apparatus 2 that can be used.

[0019] [Material Layer Forming Apparatus 1] FIG. 2 is a diagram schematically showing the configuration of the material layer forming apparatus 1. Hereinafter, both the first particle P1 and the second particle P2 refer to the above-described positive electrode active material. The first particle P1 and the second particle P2 are preferably composed of the same kind of elements.

[0020] The material layer forming apparatus 1 includes a first storage container 21a for storing and supplying the first base material 11a, a first belt device 22a for transporting the first base material 11a, and a pattern forming device 23 for forming an uneven pattern on the first base material 11a. The material layer forming apparatus 1 includes a first filling device 24a for disposing the first particles P1 in the concave portions of the uneven pattern formed on the first base material 11a. The material layer forming apparatus 1 includes a second storage container 21b for storing and supplying the second base material 11b, and a second belt device 22b for transporting the second base material 11b. The material layer forming apparatus 1 has a transfer portion 25a in which rollers 223 included in the first belt device 22a and the second belt device 22b face each other, and the first particles P1 are transferred from the first base material 11a to the second base material 11b at the transfer portion 25a. Further, the material layer forming apparatus 1 includes a second filling device 24b for disposing the second particles P2 in a non-transfer portion on the second base material 11b. Note that devices having low relevance in explaining the effects of the present case, such as a peeling and recovery device for peeling and recovering the first base material 11a after transfer from the first belt device 22a and each cleaning device, are omitted from the illustration and detailed description.

[0021] In the material layer forming apparatus 1, the pattern forming device 23, the first filling device 24a, and the transfer portion 25a correspond to a first arranging means for arranging the first particles P1 in a pattern on the second base material 11b. Further, the second filling device 24b corresponds to a second arranging means for arranging the second particles P2 in a region where the first particles P1 are not arranged on the second base material 11b.

[0022] Hereinafter, a method for forming the material layer 12 on the base material 11 by the material layer forming apparatus 1 will be described along the flow for each process.

[0023] First, a first base material 11a is supplied from a first storage container 21a to a first belt device 22a by a supply means (not shown).

[0024] When an ultraviolet curable liquid is applied by a pattern forming device 23 (described later), at least the surface material of the first base material 11a is preferably composed of a material with high wettability to the ultraviolet curable liquid. Also, the surface of the first base material 11a is preferably smooth. As the first base material 11a, a resin sheet such as polyester that has been subjected to hydrophilic treatment or lipophilic treatment according to the ultraviolet curable liquid (aqueous or oil-based) to be used can be used. Note that the first base material 11a may be a base material that is individually cut like cut paper, or a continuous base material wound in a roll like roll paper, or a continuous base material that is alternately folded like continuous paper.

[0025] The first belt device 22a conveys the supplied first base material 11a to the pattern forming position of the pattern forming device 23. The first belt device 22a includes drive rollers 221a, 222a, a pressure roller 223a, and a belt-shaped conveying member 224a suspended therefrom. At that time, the pressure roller 223a rotates in a driven manner.

[0026] The conveying member 224a is preferably selected from resin, metal, etc. For example, a resin belt made of polyimide can be used. The drive rollers 221a, 222a are preferably metal rollers made of metal. For example, metal rollers made of stainless steel can be used. The pressure roller 223a is preferably a soft roller having an elastic layer on its surface. For example, a soft roller in which a silicone rubber elastic layer is provided on the surface of a stainless steel core can be used.

[0027] Note that although the first belt device 22a is used as the conveying device for conveying the first base material 11a, a roller device can also be used instead of the belt device. The same applies to the second belt device 22b described later.

[0028] The pattern forming device 23 forms a fine concavo-convex pattern on the first substrate 11a conveyed to the pattern forming position. As a method for forming the concavo-convex pattern, a UV imprint method, a thermal imprint method, a UV inkjet method, a printing method, a laser etching method, etc. can be used. When the pattern forming device 23 forms a concavo-convex pattern by the UV imprint method, the pattern forming device 23 has a coating means for coating a UV curable liquid on the first substrate 11a. Further, the pattern forming device 23 has an imprinting means for imprinting a mold having a concavo-convex pattern formed on its surface onto the UV curable liquid on the first substrate 11a, and a light source for irradiating the UV curable liquid with ultraviolet rays. Typically, as the UV curable liquid, a UV curable liquid silicone rubber (PDMS) or a resin can be used, as the mold, a film mold can be used, and as the light source, a UV lamp can be used.

[0029] When the first filling device 24a fills the recesses with the first particles P1 using the carrier S1 carrying the first particles P1, the opening diameter of the recesses of the concavo-convex pattern on the first substrate 11a is preferably larger than the cumulative 50% particle size (median diameter) based on the volume of the first particles P1. Further, the opening diameter of the recesses is preferably smaller than the average size of the carrier S1. Here, the opening diameter of the recesses of the concavo-convex pattern is preferably the opening diameter in the short side direction of the recesses, and more preferably the maximum opening diameter in the short side direction of the recesses. Thereby, the first particles P1 can contact the bottom (typically the bottom surface) of the recesses of the concavo-convex pattern, and the carrier S1 cannot contact the bottom of the recesses. Thereby, the first particles P1 that have contacted the bottom of the recesses can be captured by the concavo-convex pattern, while on the other hand, the carrier S1 can be prevented from being captured by the concavo-convex pattern. In other words, it is preferable that the first particles P1 can contact the bottom of the recesses of the concavo-convex pattern and the first carrier S1 cannot contact the bottom of the recesses of the concavo-convex pattern.

[0030] Note that although the uneven pattern is formed on the first substrate 11a by the pattern forming device 23, a substrate with an uneven pattern pre-formed on its surface may be used as the first substrate 11a. Further, the uneven pattern may be directly formed on the surface of the conveying member 224a of the first belt device 22a by the pattern forming device 23, or a conveying member having an uneven pattern on its surface may be used as the conveying member 224a. In this case, in view of durability, a metal belt such as stainless steel or aluminum is used, and it is preferable to form an uneven pattern on the surface by a microfabrication technique such as laser etching, wet etching, or dry etching.

[0031] The first substrate 11a having an uneven pattern formed on its surface is conveyed by the first belt device 22a to the filling position of the first filling device 24a.

[0032] FIG. 3 is a diagram schematically showing the configuration of the filling device. Hereinafter, the configuration of the first filling device 24a will be described, but the same applies to the second filling device 24b.

[0033] The first filling device 24a includes a filling container 242a that stores the filler 241a, a stirring screw member 243a that stirs and conveys the filler 241a, a recovery member 244a that recovers the filler, and a magnetic member 247a.

[0034] The filler 241a includes first particles P1 and a carrier S1 that carries the first particles P1. The filler 241a is a mixture of a plurality of powders including a powder composed of a plurality of first particles P1 and a powder composed of a plurality of carriers S1. The filler 241a stored in the filling container 242a is sufficiently mixed and triboelectrically charged when being stirred and conveyed by the stirring screw member 243a. As a result, the first particles P1 are carried on the surface of the carrier S1.

[0035] The supporting material S1 is magnetic particles. The supporting material S1 is preferably particles obtained by coating the surface of ferrite core particles or resin particles in which a magnetic material is dispersed with a resin composition. The particle size and material of the supporting material S1 are appropriately selected according to the particle size and material of the first particles P1. Thereby, the first particles P1 can be stably supported.

[0036] The recovery member 244a has a roller 245a that can rotate in the direction of arrow d2 in the figure, and a magnet 246a that is disposed inside the roller 245a and fixed to the filling container 242a. Further, the magnetic member 247a is disposed to face the filling container 242a via the conveying member 224a, and has a magnet 248a inside thereof. The magnet 246a has a plurality of N poles and S poles alternately arranged along the rotation direction of the recovery member 244a. The magnet 248a has a plurality of N poles and S poles alternately arranged along the conveying direction of the conveying member 224a. Further, the magnet 246a has a magnetic pole of a different polarity (N1 pole in this embodiment) at a position closest to and facing the most downstream magnetic pole (S1 pole in this embodiment) of the magnet 248a, and an N2 pole of the same polarity as the N1 pole is arranged at the most downstream position. Note that the magnet 246a and the magnet 248a may be composed of a plurality of magnets, and the types of magnets constituting the magnet 246a and the magnet 248a are not particularly limited. For example, permanent magnets such as ferrite magnets, neodymium magnets, rare earth magnets such as samarium cobalt magnets, and plastic magnets, or means for generating a magnetic field such as an electromagnet can be used. Note that the magnet 248a may be configured to be movable in the conveying direction of the first base material 11a or the opposite direction.

[0037] Note that a regulating member for regulating the filler 241a on the first base material 11a, or a recovery member for recovering again the filler 241a that cannot be completely recovered by the recovery member 244a, may be provided upstream or downstream of the recovery member 244a in the conveying direction of the conveying member 224a. As the recovery member for recovering again, in addition to a member similar to the recovery member 244a, a recovery member that performs recovery by air blowing using a simple member such as a fixed magnet or a regulating member can be used.

[0038] Next, a process of filling the recesses on the first base material 11a with the first particles P1 by the first filling device 24a will be described with reference to FIGS. 3 to 5.

[0039] When the first conveying member 224a moves in the direction of the solid arrow d1 in FIG. 3, the first base material 11a carried and conveyed by the first conveying member 224a is conveyed and conveyed to the filling position of the first filling device 24a.

[0040] The filler 241a is conveyed by the stirring screw member 243a and supplied onto the first base material 11a (dotted line a in FIG. 3). At this time, a magnetic field is formed by the magnetic member 248a and the recovery member 244a, and the filler 241a containing the carrier S1 which is a magnetic particle forms a plurality of magnetic spikes on the first base material 11a by the magnetic field. The filler 241a supplied onto the first base material 11a is conveyed on the first base material 11a in a state where magnetic spikes are formed as the first base material 11a moves (dotted line b in FIG. 3).

[0041] FIG. 4 is a schematic diagram of the filler 241a conveyed on the first base material 11a. For the sake of explanation, the filler 241a other than the filler forming one magnetic spike is not shown. The filler 241a on the first base material 11a forms magnetic spikes along the magnetic force lines of the formed magnetic field as described above, and is conveyed while changing the shape of the magnetic spikes as shown in FIGS. 4(a), 4(b), and 4(c) as the first base material 11a moves. At this time, since a particularly strong magnetic force acts in the vicinity of the magnet 248a, the conveying speed v2 of the filler 241a is smaller than the moving speed v1 of the first base material 11a when the filler 241a moves away from the magnetic pole, and is larger in the opposite case. That is, the filler 241a on the first base material 11a has a non-zero relative speed with respect to the first base material 11a.

[0042] FIG. 5 is an enlarged view of the vicinity of the surface of the first base material 11a in FIG. 4. Although not shown in FIG. 4, as shown in FIG. 5, an uneven pattern 111a is formed on the first base material 11a. The filler 241a contacts the uneven pattern 111a and is conveyed together with the first base material 11a while having a non-zero relative speed with respect to the first base material 11a while receiving a magnetic force (solid line Fm in the figure) in a direction perpendicular to the surface of the first base material 11a. Thereby, the first particles P1 carried on the carrier S1 are conveyed while being rubbed against the uneven pattern 111a on the surface of the first base material 11a. At this time, since the particle size of the first particles P1 is smaller than the opening diameter of the concave portion of the uneven pattern 111a and the particle size of the first carrier S1 is larger than the opening diameter of the concave portion, the first particles P1 can contact the bottom surface (bottom portion) of the concave portion of the uneven pattern 111a, but the carrier S1 cannot contact. That is, only the first particles P1 in the filler 241a selectively contact the bottom surface of the concave portion. The first particles P1 that have contacted the bottom surface of the concave portion are strongly constrained by the physical restraining force due to the structure of the uneven pattern 111a and the electrostatic adhesion force and adhesive force with the structural material constituting the first base material 11a and the uneven pattern 111a, and are detached from the carrier S1.

[0043] Downstream of the magnetic member 247a, as shown in FIG. 3, a recovery member 244a is arranged with a gap from the first conveying member 224a. As the first base material 11a moves, the filler 241a conveyed near the most downstream magnetic pole (S1 pole) of the magnet 248a is affected by the magnetic field formed by the magnet 246a and moves from the first base material 241a to the recovery member 244a and is recovered (dotted line c in FIG. 3).

[0044] As described above, in the conveying process (dotted lines a, b, c in FIG. 3), the concave portions of the uneven pattern 111a on the surface of the first base material 11a are in sufficient contact with a plurality of fillers 241a. Therefore, the first particles P1 are selectively and densely arranged in the concave portions of the uneven pattern 111a after the filler 241a is recovered by the recovery member 244a.

[0045] In FIGS. 4 and 5, all the first particles P1 are illustrated with the same particle size. However, in reality, there is a particle size distribution, and furthermore, depending on the material, secondary particles formed by aggregation may exist. Even in such cases, only the particles that can contact the bottom surface of the concave portion of the uneven pattern 111a are selectively and densely filled, so coarse powders and secondary particles that may have an adverse effect on the formation of the material layer are excluded.

[0046] Thus, the filling amount of the first particles P1 into the concave portion of the uneven pattern 111a can be controlled by the size (area, width, depth) of the concave portion and the particle size of the first particles P1. Specifically, the area of the concave portion becomes the substantially filling area, and the layer thickness of the filled first particles P1 is determined by the depth of the concave portion. For example, in order to obtain a thin layer (single layer) of 50% with respect to the substrate area, the area ratio of the concave portion (the area ratio of the concave portion to the entire uneven pattern) may be controlled to 50%, and the depth of the concave portion may be controlled to be equal to or less than the particle size of the first particles P1. At this time, the opening width of the concave portion is made larger than the median diameter of the first particles P1 and smaller than the average size (here, the average particle size) of the carrier S1. Note that the first particles P1 may have a broad particle size distribution, but the carrier S1 preferably has a narrow particle size distribution, and more preferably is monodisperse. Thereby, it is easy to prevent the carrier S1 from contacting the bottom (or bottom surface) of the concave portion. If the carrier S1 can contact the bottom of the concave portion, there is a risk that the carrier S1 will also be restricted and filled in the concave portion.

[0047] Furthermore, it is preferable that the opening width of the concave portion of the uneven pattern 111a is smaller than four times the particle diameter of the first particles P1. By making the opening width smaller than four times the particle diameter of the first particles P1, the probability that the first particles P1 come into contact with both the bottom surface and the side wall surface of the concave portion of the uneven pattern 111a can be increased. In this way, the first particles P1 that are in multi-point contact with the uneven pattern 111a are strongly constrained by the uneven pattern 111a, so that the filling efficiency of the first particles P1 into the uneven pattern 111a can be increased. The same applies to the particle diameter of the second particles P2 described later and the size of the concave portion of the uneven pattern formed by the first particles P1. Also, when brush fibers are used as the carrier, the "average particle diameter of the carrier" in the above description becomes the "average fiber diameter of the carrier".

[0048] The filler 241a recovered by the recovery member 244a is conveyed by the rotating roller 244a (dotted line d in FIG. 3). The filler 241a conveyed by the roller 244a falls into the filling container 242a under the influence of a magnetic field formed by two like-pole magnetic poles (N1, N2) that are adjacent and repel each other, and gravity (dotted line e in FIG. 3). Thereafter, it is again agitated and conveyed by the agitation screw member 243a, and this is repeated thereafter.

[0049] The weight ratio of the first particles P1 to the carrier S1 in the filler 241a in the filling container 242a is determined by an inductance sensor that measures using magnetic permeability, which is common in electrophotographic devices, a patch density sensor that measures and predicts the reflection density on a base material, or the like. Then, at least one of the first particles P1 and the carrier S1 is replenished by a replenishing means (not shown) as necessary. Thereby, stable filling over a long period becomes possible.

[0050] Here, a filling device that forms a so-called magnetic brush by using magnetic particles as a carrier and fills the concave portion with a particle material has been described, but the type of the filling device is not limited to this. Brush fibers can also be used as the carrier. Alternatively, an elastic material in which at least the surface is made of an elastic body can be used as the carrier.

[0051] FIG. 6(a) is a diagram schematically showing the configuration of the filling device 24c when brush fibers are used as the carrier material.

[0052] The filling device 24c has a roller 2410 having brush fibers on its surface. The roller 2410 is a so-called brush roller with brush fibers implanted on its surface. As the material of the fibers constituting the brush fibers of the roller 2410, for example, nylon, rayon, acrylic, vinylon, polyester, vinyl chloride, etc. can be used. For the purpose of adjusting the chargeability and rigidity, the surface of the fibers may be surface-treated.

[0053] The filling device 24c has a supply member for supplying the filler 241a to the roller 2410. The filler 241a contains a powder composed of a plurality of first particles P1 and is housed in a filling container 242a. Also in this example, the filler 241a does not contain the carrier material S1 which is magnetic particles. The filler 241a is agitated and conveyed by an agitation screw member 243a and supplied to the supply member 249.

[0054] The supply member 249 is a member for supplying the filler 241a to the roller 2410, and its configuration is not particularly limited. As the supply member 249, for example, a roller at least the surface of which is made of a porous foam material having elasticity can be used. Typically, an elastic sponge roller having a foam skeleton structure and formed with a relatively low-hardness polyurethane foam on a mandrel can be used. In addition, as the material of the foam material, various rubber materials such as nitrile rubber, silicone rubber, acrylic rubber, hydrin rubber, and ethylene propylene rubber can be used in addition to urethane.

[0055] The supplied filler 241a is filled into the foam material on the surface of the supply member 249 and conveyed to the supply part that contacts the roller 2410. At the supply part, the filler 241a filled into the foam material is charged by contact with the brush fibers of the roller 2410 and carried by the brush fibers of the roller 2410. Further, the supply member 249 may also have a function of scraping off and refreshing the filler 241a remaining on the roller 2410. The filler 241a supplied to the roller 2410 contacts the first base material 11a due to the movement of the brush fibers.

[0056] At this time, the first particles P1 in the filler 241a can contact the bottom surface of the recess of the concavo-convex pattern 111a on the surface of the first base material 11a, but the brush fibers are prevented from contacting. That is, the fiber diameter of the brush fibers is made larger than the opening width of the recess of the concavo-convex pattern 111a. The fiber diameter of the brush fibers can be measured from an image of the brush fibers obtained through the glass by applying the glass to the surface of the roller 2410 and using an optical microscope. At this time, the fiber diameters of about 100 brush fibers are measured, the fiber diameter distribution is measured, and the average diameter is calculated.

[0057] Due to the movement of the conveying member 224a and / or the rotation of the roller 2410, the brush fibers of the roller 2410 are rubbed against the surface of the first base material 11a. As a result, the first particles carried by the brush fibers are densely arranged in the recesses of the concavo-convex pattern 111a on the surface of the first base material 11a.

[0058] FIG. 6(b) is a diagram schematically showing the configuration of the filling device 24d when an elastic material is used as the carrier.

[0059] The filling device 24d has the same configuration as the filling device 24c, but is different in that a roller 2411 having an elastic material is used instead of a roller 2410 having brush fibers. The roller 2411 is a roller having an elastic layer formed on its surface. The elastic layer is formed of a material having elasticity such as a rubber material such as silicone rubber, acrylic rubber, nitrile rubber, urethane rubber, or fluororubber. The elastic layer may be formed by adding fine particles such as spherical resin to control the surface shape. When the elastic layer has convex portions on its surface, the size of the convex portions of the elastic layer is made larger than the size of the concave portions of the uneven pattern 111a on the surface of the first base material 11a. The size of the convex portions of the elastic layer can be measured in the same manner as the fiber diameter of the above-described brush fibers.

[0060] By the movement of the transport member 224a and / or the rotation of the roller 2411, the elastic material on the surface of the roller 2411 is rubbed against the surface of the first base material 11a. As a result, the first particles carried by the elastic material are densely arranged in the concave portions of the uneven pattern 111a on the surface of the first base material 11a.

[0061] By using brush fibers or an elastic material as the carrier material as shown in FIGS. 6(a) and 6(b), it is not necessary to include magnetic particles in the filler, and the configuration of the filling device can be simplified. On the other hand, when magnetic particles are used as the carrier material as shown in FIG. 3, the degree of freedom in the size and shape of the carrier material is higher than in the case of brush fibers or an elastic material. Also, in the case of magnetic particles, the degree of freedom in the movement of the carrier material on the base material is high. For these reasons, when magnetic particles are used as the carrier material, particles such as the first particles P1 can be supplied more efficiently onto the base material and filled more efficiently into the concave portions on the base material. Also, when a magnetic material is used as the carrier material, even if the carrier material deteriorates during the process, the carrier material can be replenished or replaced without stopping the process.

[0062] According to the method of filling the recesses with particles by rubbing a carrier material carrying the particles, compared with the filling method using a restricting member such as a blade, more dispersed particles can be supplied to the recesses, and filling can be performed stably and densely. This merit becomes more prominent as the particle size of the particles to be filled is smaller because the particles are more likely to aggregate.

[0063] The first base material 11a filled with the first particles 1 in the recesses of the concavo-convex pattern 111a by the first filling device 24a is conveyed to the transfer portion 25a by the first belt device 22a.

[0064] Here, as shown in FIG. 2, the second belt device 22b has drive rollers 221b and 222b, a pressure roller 223b, and a belt-like conveying member 224b suspended therefrom, similar to the first belt device 22a. At this time, the pressure roller 223b rotates in a driven manner. In the transfer portion 25a, the pressure roller 223a of the first belt device 22a and the pressure roller 223b of the second belt device 22b face each other.

[0065] The second base material 11b is supplied to the second belt device 22b from the second storage container 21b and conveyed in the direction of the arrow in FIG. 2. The supplied second base material 11b is conveyed in accordance with the timing when the first base material 11a is conveyed to the transfer portion 25a. In the transfer portion 25a, the first particles P1 filled in the first base material 11a are transferred to the second base material 11b. That is, the first base material 11a can also be referred to as a transfer base material for transferring the first particles P1 to the second base material 11b. Also, the concavo-convex pattern formed on the surface of the first base material 11a can also be referred to as a transfer concavo-convex pattern. Hereinafter, this transfer process will be described with reference to FIG. 7.

[0066] FIG. 7 is a diagram schematically showing the configuration of the transfer unit 25a. The transfer unit 25a is composed of a pressure roller 223a and a conveying member 224a of the first belt device 22a, and a pressure roller 223b and a conveying member 224b of the second belt device 22b. As described above, the pressure rollers 223a and 223b rotate passively, and the two rollers are in contact via the conveying members 224a and 224b. At least one of the pressure rollers 223a and 223b is a soft roller having an elastic layer on the surface layer, and a nip portion is formed at the portion where the two rollers are in contact.

[0067] The first substrate 11a filled with the first particles P1 by the first filling device 24a and the second substrate 11b are conveyed at substantially the same speed by their respective conveying members (224a, 224b), and enter the nip portion formed by the contact of the pressure rollers 223a and 223b. In the nip portion, the first particles P1 on the first substrate 11a come into contact with the second substrate 11b and are transferred onto the second substrate 11b.

[0068] The second substrate 11b is a substrate having an adhesive force to the first particles P1 greater than the adhesive force of the first substrate 11a to the first particles P1. In other words, the adhesive force of the first particles P1 to the second substrate 11b is greater than the adhesive force of the first particles P1 to the first substrate 11a. Thereby, in the nip portion, the first particles P1 on the first substrate 11a are transferred onto the second substrate 11b.

[0069] The material of the second substrate 11b is not particularly limited, and a substrate of the same material as the first substrate 11a can be used. Note that the second substrate 11b may also be a substrate that is individually cut off like cut paper, similar to the first substrate 11a, or a continuous substrate wound in a roll like roll paper, or a continuous substrate alternately folded like continuous paper.

[0070] The second substrate 11b is preferably subjected to a surface treatment for enhancing the adhesive force in order to transfer the contacted first particles P1. For example, the second substrate 11b preferably has an adhesive layer with an adhesive applied to its surface. Further, the back surface of the second substrate 11b (the surface where the material layer is not formed) preferably also has an adhesive layer with the same adhesive as the surface applied thereto. Thereby, it is possible to prevent displacement between the substrates during lamination, and since the positive electrode active material on the substrate is sandwiched between the same materials on the upper and lower surfaces (lamination direction), variations in the deposition state (direction and length) of the protrusions deposited from the positive electrode active material are reduced.

[0071] The adhesive may be an acrylic adhesive, a rubber adhesive, a silicone adhesive, or may be a thermoplastic resin or a photocurable resin whose adhesive force changes due to disturbances such as heat or light. Note that the adhesive may be applied to both surfaces of the second substrate 11b.

[0072] Further, the material layer forming apparatus 1 may have an application means such as a dispenser or an inkjet head for applying an adhesive to the surface of the second substrate 11b during conveyance.

[0073] The type and application amount of the adhesive are appropriately adjusted according to the shape and material of the uneven pattern to be used, the particle diameters and materials of the first particles P1 and the second particles P2, etc., but it is preferable that the adhesive force of the adhesive is greater than that of the uneven pattern 111a. The comparison of the adhesive force can be measured by a general method using a nanoindenter.

[0074] In the nip portion, the first particles P1 are constrained by the adhesive force generated between the first particles P1 and the second substrate 11b. When the two conveying members 224a and 224b are separated after passing through the nip portion, the first particles P1 on the first substrate 11a are transferred to the second substrate 11b.

[0075] The second substrate 11b onto which the first particles P1 are transferred is conveyed by the conveying member 224b to the filling position of the second filling device 24b.

[0076] The second filling device 24b has the same configuration and function as the first filling device 24a, except that a filler 241b having second particles P2 and a carrier S2 is accommodated in the filling container 242a instead of the filler 241a having first particles P1 and a carrier S1.

[0077] The second filling device 24b fills the second particles P2 in a portion of the second substrate 11b where the first particles P1 are not disposed. As described above, the first particles P1 are disposed on the second substrate 11b that has passed through the transfer unit 25a, but a recess is formed in a portion where the first particles P1 are not disposed. The second filling device 24b fills the second particles P2 into this recess by the same process as the first filling device 24a. In this way, by selectively filling the second particles P2 that can be filled into the voids where the first particles P1 are not disposed on the substrate 11b, the coverage rate of the substrate by the particles is improved. The second particles P2 preferably have a median diameter that is equal to or less than the opening width of the voids between the first particles P1. Here, the case where magnetic particles are used as the carrier is described, but similar to the first filling device 24a, brush fibers or elastic materials may be used as the carrier.

[0078] The filler 241b has second particles P2 and a carrier S2 that supports the second particles P2. The filler 241b is a mixture of a plurality of powders including a powder composed of a plurality of second particles P2 and a powder composed of a plurality of carriers S2. As the carrier S2, the same one as the carrier S1 can be used.

[0079] FIG. 8 is an enlarged view of the vicinity of the surface of the second substrate 11b in the filling process by the second filling device 24b. On the second substrate 11b, there is formed an uneven pattern having convex portions formed by arranging the first particles P1 and concave portions where the first particles P1 are not arranged. The filler 241b contacts this uneven pattern and, while receiving a magnetic force (solid line Fm in the figure) in a direction perpendicular to the surface of the second substrate 11b, has a non-zero relative velocity with respect to the second substrate 11b and is conveyed together with the second substrate 11b. As a result, the second particles P2 carried on the carrier S2 are conveyed while being rubbed against the uneven pattern on the surface of the second substrate 11b. At this time, the opening width of the concave portion of the uneven pattern formed on the second substrate 11b is set to a size such that the second particles P2 can contact the bottom surface (second substrate 11b) of the concave portion, but the carrier S2 cannot contact it. Thereby, only the second particles P2 in the filler 241b selectively contact the bottom surface (second substrate 11b) of the concave portion. The second particles P2 that have contacted the bottom surface of the concave portion are strongly constrained by the physical restraint force due to the structure of the uneven pattern and the electrostatic adhesion force and adhesive force with the second substrate 11b and the structural material (here, the first particles P1) constituting the uneven pattern, and are detached from the carrier S2.

[0080] FIG. 9(a) is a diagram schematically showing the second substrate 11b after the first particles P1 are transferred by the transfer portion 25a, and is a view of the second substrate 11b seen from a direction perpendicular to the substrate surface. As shown in FIG. 9(a), on the second substrate 11b, there is formed a honeycomb pattern in which arrangement regions where the first particles P1 are arranged in a regular hexagonal shape are aligned. The first particles P1 are densely arranged within this regular hexagonal region, and the first particles P1 are not arranged in the other portions (the white portions in FIG. 9(a)), and the surface of the second substrate 11b is exposed. The regular hexagonal region where such first particles P1 are held is the first pattern portion, and the region of the honeycomb pattern where the second particles P2 are held and which corresponds to the gaps between the first pattern portions is the second pattern portion.

[0081] FIG. 9(b) is a diagram schematically showing the second base material 11b after the second particles P2 are filled by the second filling device 24b, and is a view of the second base material 11b seen from a direction perpendicular to the base material surface. As shown in FIG. 9(b), the second particles P2 are densely arranged in the region where the first particles P1 are not arranged. Also, the first particles P1 and the second particles P2 are densely arranged at the boundary between the region where the first particles P1 are arranged and the region where the second particles P2 are arranged. Note that particles can be filled in a similar manner even in the slight gaps between the first particles P1. In this case, it is possible to fill using a filler containing particles having a particle size corresponding to the gaps between the first particles P1 by the same method as described above, and a denser thin film can be formed.

[0082] It is preferable that a liquid containing a material to which the positive electrode active material can adhere is applied to the base material 11. Further, it is preferable to use the base material 11 containing a material to which the positive electrode active material can adhere.

[0083] [Material layer forming apparatus 2] FIG. 10 is a diagram schematically showing the configuration of the material layer forming apparatus 2. The material layer forming apparatus 2 is an apparatus for forming a material layer 12 on the base material 11, and includes a storage container 21 for storing and supplying the base material 11, and a belt device 22 for transporting the base material 11. The material layer forming apparatus 2 also includes a liquid application device 201 for disposing a liquid on the base material 11. At that time, in order to densely arrange the positive electrode active material on the base material 11, it is preferable to dispose the liquid on the base material 11 in a pattern.

[0084] As the liquid application device 201, a device that discharges a liquid by an inkjet method or a device that applies a liquid can be used, but a plate method such as a flexographic plate can also be used. Among them, as the liquid application device, it is preferable to use a device that discharges a liquid by an inkjet method.

[0085] As the device that discharges a liquid by an inkjet method, for example, devices with various discharge methods such as a thermal type, a piezo type, an electrostatic type, and a continuous type can be used.

[0086] As the liquid applied by the liquid application device 201, it may be aqueous or oily as long as it contains a material capable of adhering the positive electrode active material. Further, the liquid application device 201 may form the pattern L1 with a plurality of types of liquids. For example, the liquid application device 201 may apply two types of liquids that react with the base material 11 to enhance adhesiveness. Examples of the material capable of adhering the positive electrode active material include resins such as acrylic resin.

[0087] The powder application device 202 applies a powder containing a positive electrode active material to the base material 11 on which the liquid is arranged in a pattern. Thereby, the positive electrode active material is fixed by the material capable of adhering the positive electrode active material in the liquid on the base material 11, and the positive electrode active material is fixed in a pattern corresponding to the pattern L1.

[0088] As the means for applying the powder by the powder application device 202, means for spraying the powder toward the base material 11 or means for sprinkling can be used. The powder application device 202 may further include means for removing the positive electrode active material that has not been fixed to the base material 11 by the liquid by means such as vibration, blowing, or suction.

[0089] The material layer forming device 2 may further include a drying device that evaporates at least a part of the liquid applied by the liquid application device 201 to control the amount of the liquid on the base material 11, the thickness of the pattern L1, and the like. This drying device may be provided on the downstream side of the liquid application device 201 and on the upstream side of the powder application device 202.

[0090] Further, the material layer forming device 2 may further include heating means for heating the base material 11 to which the positive electrode active material has been applied by the powder application device 202. As the heating method of the heating means, a contact type heat roller may be used, or a non-contact type method of irradiating infrared rays or microwaves may be used. In addition, it is also possible to heat by scanning an energy ray such as a laser beam. Note that the heating means may be provided on the back side of the belt 224 included in the belt device 22, or may be provided on the front side (the side on which the base material 11 is supported).

[0091] In order to densely arrange particles on the substrate, it is preferable to apply a liquid to the entire surface of the substrate and arrange the second particles P2 in the region where the first particles P1 are not arranged using the second filling device 24. Similarly to the material layer forming device 1, the material layer forming device 2 preferably has a transfer portion. Transfer the first particles P1 from the substrate 11 to another substrate having an adhesive layer, and in the substrate onto which the first particles P1 are transferred, use the second filling device 24 in the region where the first particles P1 are not arranged. Thus, the second particles P2 can be arranged. As a result, it becomes possible to densely arrange particles on the substrate.

[0092] In the material layer forming devices 1 and 2, the coverage rate of the substrate by the active material is preferably 60% or more, more preferably 70% or more, and even more preferably 80% or more. The coverage rate of the substrate by the active material can be measured by photographing the region where the material layer is formed from the vertical direction of the substrate with an optical microscope and calculating the area ratio of the positive electrode active material in the region using image processing software.

[0093] In this way, by increasing the coverage rate of the substrate by the active material, it is easy to manufacture an active material having protrusions deposited in a plurality of directions. The reason is presumed as follows. During the sintering process in the third step described later, the substrate gasifies. It is considered that the more easily the active material comes into contact with the gas, the more easily the active material deposits protrusions. When the coverage rate of the substrate by the active material is high, the active materials are densely arranged, the gaps between the active materials become small, and the active materials are more likely to come into contact with the gas. On the other hand, when the coverage rate of the substrate by the active material is low, the active materials are sparsely arranged, the gaps between the active materials become large, and the active materials are less likely to come into contact with the gas.

[0094] (Second Step) The second step is a step of forming a laminate by laminating a plurality of material layers. The laminate is preferably formed by laminating three or more material layers.

[0095] FIG. 11 is a diagram schematically showing the configuration of a laminate forming apparatus. The laminate forming apparatus includes a transfer device 31 that transfers a substrate 11 on which a material layer 12 is formed, and a stage 32 that can move vertically forward and backward by an actuator (not shown).

[0096] The transfer device 31 receives the substrate 11 having the material layer 12 formed using a material layer forming device and transfers it to the stage 32. Examples of the transfer device 31 capable of transferring the substrate 11 include a belt conveyor, rollers, a robot arm, and the like.

[0097] When the substrate 11 is transferred to the stage 32 by the transfer device 31, the stage 32 moves vertically by the thickness of the substrate 11 and the material layer 12. By repeating the transfer by the transfer device 31 and the movement of the stage 32, a plurality of substrates 11 each having the material layer 12 formed thereon are laminated to form a laminate 13.

[0098] It is preferable to have a static elimination step of eliminating static electricity from the substrate between the first step and the second step. In the first step, the substrate and the particles on the substrate are easily charged, and an electrostatic repulsive force is generated between the substrates when laminating. Therefore, when laminating in the second step, the substrate is likely to peel off, or a gap is likely to form between the substrates. As a result, it is considered that the active material is less likely to come into contact with the gas, and the active material is less likely to deposit on the protrusions. In the static elimination step, it is preferable to perform non-contact static elimination using an electrostatic elimination blower or the like.

[0099] (Third Step) The third step is a step of sintering the laminate to produce a positive electrode active material.

[0100] FIG. 12 is a diagram schematically showing the configuration of a sintering apparatus. The sintering apparatus includes a transfer device 41 that transfers the laminate 13, and a heating furnace 42 that heats the laminate 13.

[0101] The transfer device 41 receives the laminate 13 from the laminate forming device and transfers it to the heating furnace 42. The transfer device 41 is preferably a device capable of transferring the laminate 13, similar to the transfer device 31. Examples of devices capable of transferring the laminate 13 include a belt conveyor, rollers, and a robot arm.

[0102] The heating furnace 42 is a furnace for heating the laminate 13. The heating furnace 42 includes a heating means 421, a pressing means 422, and an atmosphere adjusting means 423. As the heating furnace 42, a firing furnace used for firing ceramics or the like can be used. The pressing means 422 presses the laminate 13 being heated in the heating furnace 42 or presses the laminate 13 before and after heating. Note that the pressing portion of the pressing means 422 for pressing the laminate 13 is preferably formed of a porous body that allows gas to pass through easily. The atmosphere adjusting means 423 includes an atmosphere gas supply means 423a and a pressure reducing means 423b, and adjusts the atmosphere gas in the processing space of the heating furnace 42.

[0103] When sintering the laminate, it is preferably heated at a temperature equal to or higher than the thermal decomposition temperature of the base material 11 in the laminate 13, and preferably heated at a temperature lower than the thermal decomposition temperature of each material layer in the laminate 13. The temperature for heating the laminate is preferably 300°C or higher and 1000°C or lower, and more preferably 400°C or higher and 800°C or lower. When the laminate 13 contains a plurality of types of base materials 11 made of different materials, the heating temperature may be set to a temperature equal to or higher than the highest thermal decomposition temperature among the thermal decomposition temperatures of the plurality of base materials.

[0104] Thereby, it becomes possible to selectively decompose the base material in the laminate to remove the base material and manufacture a positive electrode active material having protrusions deposited in a plurality of directions. Here, in the laminate before heating, the positive electrode active material does not have protrusions deposited in a plurality of directions. During the heating process, the positive electrode active material has protrusions protruding in a plurality of directions.

[0105] The thermal decomposition temperature refers to the temperature at which the weight loss of the material begins when the temperature is gradually increased under the atmosphere during heating in a sintering treatment apparatus. Therefore, by heating the laminate at a temperature equal to or higher than the thermal decomposition temperature of the base material 11, the base material 11 in the laminate can be decomposed to reduce its weight, and the base material 11 can be removed from the laminate. The heating temperature is preferably a temperature equal to or higher than the thermal decomposition temperature of the base material 11, but it is more preferably heated at a temperature even higher than the thermal decomposition temperature. Specifically, when performing thermogravimetric analysis by increasing the temperature from room temperature (25 °C) at a rate of 5 °C / min under the atmosphere (typically air) during heating in a sintering treatment apparatus, it is preferable to heat at a temperature equal to or higher than the temperature when it reaches 70% of the initial weight. Also, when performing the same thermogravimetric analysis, it is more preferable to heat at a temperature equal to or higher than the temperature when it reaches 50% of the initial weight, and even more preferably to heat at a temperature equal to or higher than the temperature when it reaches 20% of the initial weight. Thereby, the time required for removing the base material 11 can be shortened, or the removal rate of the base material 11 can be increased.

[0106] That is, when the sintering treatment apparatus removes the base material 11 by heating, the positive electrode active material preferably has a material with a thermal decomposition temperature higher than that of the base material 11. Generally, since inorganic materials tend to have a higher thermal decomposition temperature than organic materials, the positive electrode active material is an inorganic material, and the material of the base material 11 is preferably an organic material such as resin. Also, when the sintering treatment apparatus removes the base material 11 by heating, the positive electrode active material preferably has a softening point temperature higher than the thermal decomposition temperature of the base material 11.

[0107] The sintering treatment apparatus preferably causes 90% by weight or more of the base material in the laminate 13 to disappear by heating, more preferably 95% by weight or more to disappear, and even more preferably 97% by weight or more to disappear. At that time, the base material is preferably burned or gasified and released to the outside as a gas.

[0108] In order to deposit protrusions from the positive electrode active material in a plurality of directions, it is necessary for the gas to be in uniform contact with the positive electrode active material when the base material is gasified. For this purpose, it is preferable to densely arrange the positive electrode active material on the base material, reduce the thickness of the base material, and increase the density between particles in the stacking direction of the base material. Specifically, the thickness (μm) of the base material is preferably 10 times or less, more preferably 5 times or less, and even more preferably 2 times or less of the particle size (μm) of the positive electrode active material. Here, the thickness of the base material when it has an adhesive layer on its surface refers to the total thickness of the thickness of the adhesive layer and the thickness of the base material. Also, the particle size of the positive electrode active material refers to the cumulative 50% particle size (median diameter) based on volume. Note that the thickness of the base material can be measured using a digital thickness gauge or the like. The thickness of the adhesive layer can be measured by removing the adhesive layer on the base material with a solvent, measuring the base material with the digital thickness gauge, and measuring the difference. The particle size of the positive electrode active material can be measured using a laser diffraction / scattering particle size distribution measuring device (LA-960, manufactured by Horiba, Ltd.).

[0109] The thickness of the base material is preferably 1 μm or more and 1 mm or less. The particle size of the positive electrode active material is preferably 0.1 μm or more and 100 μm or less.

[0110] Note that by using a base material formed of an organic material such as resin as the base material, it is possible to easily remove the base material by heating. As materials constituting the base material, polyesters such as polyethylene (PE), polypropylene (PP), and polyethylene terephthalate (PET), and polyamides such as nylon can be used. Among them, from the viewpoints of decomposition temperature and low toxicity of the gas generated during thermal decomposition, it is preferable to use PET.

[0111] The sintering treatment apparatus preferably exhausts the released gas to the outside of the heating furnace 42 by the decompression means 423b. By setting the inside of the heating furnace 42 as an oxidizing atmosphere, that is, an atmosphere containing oxygen gas such as air, by means of the atmosphere gas supply means 423a or the like, the base material can be burned and removed.

[0112] When the base material is gasified by thermal decomposition and released as a gas from the laminate 13, each material layer in the laminate 13 may be pushed up and its shape may change. Therefore, when heating is performed in the heating furnace 42, the laminate 13 may be pressurized by the pressurizing means 422 before, during, or after heating, or during cooling or heat dissipation after heating. Also, after removing the base material with a sintering treatment apparatus, it may be pressurized separately with a pressurizing apparatus (for example, an isostatic pressure pressurizing apparatus) and then heated again with the sintering treatment apparatus.

[0113] It is preferable to have a pressurizing step of pressurizing the laminate between the second step and the third step. The pressurization is preferably performed at 5 MPa to 500 MPa. The state of the particles on each base material to be laminated becomes uniform, and the formation of the protrusions becomes stable. The specific pressurizing step is preferably performed by vacuum degassing, isostatic pressure pressurization, or a general hydraulic press or roller press. Among these, it is preferable to combine vacuum degassing and isostatic pressure pressurization. By performing isostatic pressure pressurization in a state where the air between the base materials forming the laminate has escaped, the voids between the active materials become smaller, the active materials are likely to come into contact with the gas, and the active materials are likely to deposit protrusions. Also, since the active materials are arranged densely, many active materials deposit protrusions, so that the active materials with deposited protrusions can be obtained in a high yield.

[0114] FIG. 13 is a diagram schematically showing the overall configuration of the additive manufacturing system. The additive manufacturing system 100 includes a control unit U1, a material layer forming unit U2, a laminating unit U3, a removing unit U4, and a post-processing unit U5. The control unit U1 is responsible for controlling each part of the additive manufacturing system 100. In the material layer forming unit U2, a material layer 12 is formed on a base material 11 using the above-described material layer forming apparatus (FIG. 2). The laminating unit U3 uses the above-described laminate forming apparatus (FIG. 11) to laminate a plurality of base materials 11 on which the material layers 12 are respectively formed in the material layer forming unit U2, and forms a laminate 13 including a plurality of material layers 12 and a plurality of base materials 11. The removing unit U4 uses the above-described sintering treatment apparatus (FIG. 12) to remove the base material 11 from the laminate 13 formed by the laminating unit U3 to form a three-dimensional object 14. The three-dimensional object 14 includes a positive electrode active material having protrusions deposited in a plurality of directions. The post-processing unit U5 performs post-processing on the three-dimensional object 14 formed by the removing unit U4. Note that the unit configuration shown in FIG. 13 is merely an example, and other configurations may be adopted. Hereinafter, the configuration and operation of each unit will be described.

[0115] [Control Unit] The control unit U1 is responsible for controlling each part of the additive manufacturing system 100, specifically, the material layer forming unit U2, the laminating unit U3, the removing unit U4, and the post-processing unit U5.

[0116] The control unit U1 may include a three-dimensional shape data input unit that receives input of three-dimensional shape data of a three-dimensional object (hereinafter sometimes referred to as a "modeling target object") to be formed by the additive manufacturing system 100 from an external device (such as a personal computer). As the three-dimensional shape data, data created and output by a three-dimensional CAD, a three-dimensional modeler, a three-dimensional scanner, etc. can be used. The file format is not limited, but for example, the STL (StereoLithography) file format can be preferably used.

[0117] The control unit U1 may include a slice data calculation unit that slices three-dimensional shape data at a predetermined pitch to calculate the cross-sectional shape of each layer, and generates image data (referred to as "slice data") used for image formation by the material layer formation unit U2 based on the cross-sectional shape. Further, the slice data calculation unit may analyze the three-dimensional shape data or the slice data of the upper and lower layers to determine the presence or absence of an overhang portion (a portion floating in the air), and add an image for the support material to the slice data as necessary.

[0118] As will be described in detail later, the material layer formation unit U2 of this embodiment uses a plurality of types of materials and can form a material layer in which each material is patterned. Therefore, data corresponding to the images of the respective materials may be generated as the slice data. As the file format of the slice data, for example, multi-value image data (each value represents the type of material) or multi-plane image data (each plane corresponds to the type of material) can be used.

[0119] Also, although not shown, the control unit U1 also includes an operation unit, a display unit, and a storage unit. The operation unit has a function of receiving instructions from the user. For example, it is possible to input power on / off, various settings of the device, operation instructions, etc. The display unit has a function of presenting information to the user. For example, it is possible to present various setting screens, error messages, operation status, etc. The storage unit has a function of storing three-dimensional shape data, slice data, various setting values, etc.

[0120] The control unit U1 can be configured by a computer that includes, in terms of hardware, a CPU (Central Processing Unit), a memory, an auxiliary storage device (such as a hard disk, flash memory, etc.), an input device, a display device, and various I / Fs. Each of the above functions is realized by the CPU reading and executing a program stored in an auxiliary storage device or the like and controlling the necessary devices. However, some or all of the above functions may be configured by circuits such as ASICs or FPGAs, or may be executed on other computers using technologies such as cloud computing or grid computing.

[0121] [Material layer forming unit] The material layer forming unit U2 is a unit that forms a material layer 12 on the base material 11. As the material layer forming unit U2, the above-described material layer forming apparatus 2 can be used.

[0122] The additive manufacturing system 100 may have a plurality of material layer forming units U2. Thereby, the formation of the material layer 12 on the base material 11 can be performed simultaneously in parallel, and the throughput of forming the laminate and the three-dimensional object can be further improved. Also, when there are a large number of types of materials constituting the three-dimensional object, by providing the material layer forming unit U2 for each material type or for each group of material types, it is also possible to omit the switching of the material type and the process within the material layer forming unit U2. Thereby, the manufacturing of the three-dimensional object can be performed continuously.

[0123] [Laminating unit] The laminating unit U3 is a unit that laminates a plurality of base materials 11 on which material layers 12 are respectively formed by the material layer forming unit U2 to form a laminate 13 including a plurality of material layers 12 and a plurality of base materials 11. The above-described laminate forming apparatus can be used.

[0124] The laminated unit U3 may further include a conveying device 33 that conveys the formed laminate 13 to a removing unit U4 or the like, and a pressing device (not shown) that presses the laminate 13 in the laminating direction. The conveying device 33 may have the same configuration as the conveying device 31.

[0125] [Removing Unit] The removing unit U4 is a unit that removes the base material 11 from the laminate 13 formed by the laminating unit U3 to form the three-dimensional object 14. The above-described sintering treatment apparatus can be used.

[0126] [Post-treatment Unit] The post-treatment unit U5 is a unit that performs post-treatment on the three-dimensional object 14 formed by the removing unit U4.

[0127] The type of post-treatment performed by the post-treatment unit U5 is not particularly limited. For example, a treatment of further heating and firing the three-dimensional object 14 can be mentioned. When the post-treatment unit U5 performs a heat treatment as a post-treatment, the removing unit U4 may also serve as that function. By firing the three-dimensional object 14, the materials such as the particulate materials in each material layer can be sintered together.

[0128] Note that the post-treatment unit U5 may also have a pressing means for heating the three-dimensional object 14, similar to the removing unit U4. The post-treatment unit U5 may press the three-dimensional object 14 by the pressing means before, during, or after the heating as a post-treatment, or during the cooling or heat dissipation after the heating.

[0129] <Electrode> The electrode contains an active material and an electrolyte, and the active material has protrusions deposited in a plurality of directions. The active material is preferably manufactured using the above-described manufacturing method. Also, the electrode can be manufactured by a method similar to the above-described manufacturing method of the active material, except that the first particles are the active material and the second particles are the electrolyte. The active material contained in the obtained electrode has protrusions deposited in a plurality of directions.

[0130] (Electrolyte) Examples of electrolytes include solid electrolytes and liquid electrolytes.

[0131] [Solid electrolyte] Examples of solid electrolytes include oxide-based solid electrolytes, sulfide-based solid electrolytes, complex hydride-based solid electrolytes, etc. Oxide-based solid electrolytes include NASICON-type compounds such as Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 and Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 ; garnet-type compounds such as Li 6.25 La 3 Zr 2 Al 0.25 O 12 ; perovskite-type compounds such as Li 0.33 Li 0.55 TiO 3 ; silicon-type compounds such as Li 14 Zn(GeO 4 ) 4 ; and acid compounds such as Li 3 PO 4 and Li 4 SiO 4 , Li 3 BO 3 . Specific examples of sulfide-based solid electrolytes include Li 2 S-SiS 2 , LiI-Li 2 S-SiS 2 , LiI-Li 2 S-P 2 S 5 , LiI-Li 2 S-P 2 O 5 , LiI-Li 3 PO 4 -P 2 S 5 , Li 2 S-P 2 S 5Examples include the like. The solid electrolyte may be crystalline, amorphous, or glass ceramics. Note that Li 2 S-P 2 S 5 such as the description of Li 2 S and P 2 S 5 means a sulfide-based solid electrolyte made using a raw material containing

[0132] [Liquid electrolyte] Examples of the liquid electrolyte include non-aqueous electrolytes. The non-aqueous electrolyte is a liquid in which about 1 mol of a lithium salt is dissolved in a non-aqueous solvent. Examples of the non-aqueous solvent include ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, and the like. Examples of the lithium salt include LiPF 6 LiBF 4 LiClO 4 and the like. An aqueous electrolyte using an aqueous solvent may also be used.

[0133] [Battery] The battery includes a positive electrode active material, a negative electrode active material, and an electrolyte. The positive electrode active material has protrusions deposited in a plurality of directions. The positive electrode active material is preferably manufactured using the above-described manufacturing method. Examples of the electrolyte include the above-described solid electrolyte and liquid electrolyte.

[0134] (Negative electrode active material) Examples of the negative electrode active material include metals, metal fibers, carbon materials, oxides, nitrides, silicon, silicon compounds, tin, tin compounds, and various alloy materials. Among them, from the viewpoint of capacity density, oxides, carbon materials, silicon, silicon compounds, tin, tin compounds, and the like are preferable. Examples of the oxide include, for example, Li 4 Ti 5 O 12(LTO: Lithium titanate) and the like can be mentioned. Examples of carbon materials include various natural graphites (graphite), coke, carbon in the process of graphitization, carbon fibers, spherical carbon, various artificial graphites, amorphous carbon, and the like. Examples of silicon compounds include silicon-containing alloys, silicon-containing inorganic compounds, silicon-containing organic compounds, solid solutions, and the like. Examples of tin compounds include SnO b (0 < b < 2), SnO 2 , SnSiO 3 , Ni 2 Sn 4 , Mg 2 Sn and the like. Further, the negative electrode material may contain a conductive assistant. Examples of the conductive assistant include graphites such as natural graphite and artificial graphite, carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black. Other examples of the conductive assistant include conductive fibers such as carbon fibers, carbon nanotubes, and metal fibers, metal powders such as carbon fluoride and aluminum, conductive whiskers such as zinc oxide, conductive metal oxides such as titanium oxide, and organic conductive materials such as phenylene dielectrics.

Example

[0135] In this example, lithium cobaltate, which is a positive electrode active material, was used as the active material. However, for other active materials, active materials having deposited protrusions can be produced by optimizing the base material and heating conditions in the same process.

[0136] Hereinafter, lithium cobaltate will be abbreviated as LCO, lithium borate as LBO, and Li 1.5 Al 0.5 Ge 1.5 (PO 4 ) 3 will be described abbreviated as LAGP.

[0137] [Manufacture of Positive Electrode Active Material] (Example 1) Using the above-described laminated manufacturing system 100, a positive electrode active material was manufactured. Specifically, in the material layer forming unit U2, the material layer forming apparatus 1 shown in FIG. 2 was used. By forming a material layer on a substrate and heating a laminate obtained by laminating the substrates on which the material layers were formed, the substrate was removed to manufacture the positive electrode active material.

[0138] As the first substrate 11a, a polyethylene terephthalate (PET) sheet was used. On the first substrate 11a, a lens array-shaped concavo-convex pattern was formed by the pattern forming apparatus 23. This lens array shape was a state in which lenses having a depth of 5.5 μm were arranged at a period of 7.5 μm.

[0139] First, an ultraviolet curable resin (ultraviolet curable liquid silicone rubber (PDMS), manufactured by Shin-Etsu Chemical Co., Ltd.) was applied onto the first substrate 11a. Thereafter, a film mold (standard mold, manufactured by Soken Chemical & Engineering Co., Ltd.) having a lens array-shaped convex pattern on the surface corresponding to the concavo-convex pattern to be formed was pressed against the ultraviolet curable resin on the first substrate 11a. While the film mold was pressed, ultraviolet rays were irradiated by a UV lamp to cure the ultraviolet curable resin, and the film mold was released.

[0140] As the second substrate 11b, a polyethylene terephthalate (PET) sheet having an acrylic adhesive applied to both the front surface (the surface on which the material layer is formed) and the back surface (the surface on which the material layer is not formed) was used. The thickness of the PET sheet was 20 μm, and the thickness of the acrylic adhesive applied to the surface of the PET sheet was 1 μm.

[0141] As the first particle and the second particle, LCO (Celsius C-5H, manufactured by Nippon Kasei Kogyo Co., Ltd.) was used. The cumulative 50% particle size (median diameter) based on the volume of LCO was 7 μm, and the median diameter was measured using a laser diffraction / scattering particle size distribution analyzer (LA-960, manufactured by Horiba, Ltd.). As the carrier S1 and the carrier S2, a standard carrier which is a magnetic particle (standard carrier P02, manufactured by The Japan Society for Imaging Science and Technology) was used. Thereby, the material layer 1 was formed. When forming the material layer 1, the ratio of the positive electrode active material in the fillers 241a and 241b was set to 17% by weight.

[0142] In the material layer 1, LCO was formed in a substantially single layer on the base material, and the coverage rate of the base material by LCO was 80%. The coverage rate of the base material by LCO was measured by photographing the region where the material layer was formed from the vertical direction of the base material with an optical microscope and calculating the area ratio of the positive electrode active material in the region using image processing software (Adobe Systems Incorporated's Photoshop (registered trademark)). Since the LCO on the base material was uniformly arranged in the in-plane direction of the base material and the stacking direction of the base material, the variation in the deposition state (direction and length) of the protrusions from the positive electrode active material was reduced. After forming the material layer on the base material, the base material was de-electrified using an electrostatic removal blower (manufactured by AS ONE Corporation).

[0143] Next, in the laminating unit U3, three second base materials 11b on which the material layer was formed were laminated on an aluminum foil (thickness: 20 μm). Thereafter, the aluminum foil on which the second base material 11b was laminated was placed in a laminate film (manufactured by Asahi Kasei Pax Co., Ltd.), subjected to vacuum lamination treatment using a vacuum packaging machine (manufactured by TOSEI Co., Ltd.), and pressurized at 200 MPa using an isostatic pressure pressurizing device (manufactured by Nikkiso Co., Ltd.). Thereby, a laminate in which three second base materials 11b on which the material layer was formed were laminated was obtained on the aluminum foil.

[0144] Next, in the removal unit U4, the substrate was removed from the laminate by heating. As the removal unit U4, an electric furnace (a tabletop muffle furnace manufactured by Yamada Denki Co., Ltd.) was used. The laminate was placed on the ceramic stage in the electric furnace and heated under non-pressure and in the atmosphere. Using a heating profile, the temperature was raised from room temperature (25°C) to 250°C at a rate of 2.5°C per minute, then from 250°C to 510°C at a rate of 0.5°C per minute. After reaching 510°C, it was maintained for 1 hour, and then cooled to room temperature (25°C).

[0145] Figure 14 is a diagram showing the thermogravimetric analysis results of PET coated with an acrylic adhesive, which is the second substrate 11b. The thermogravimetric analysis was performed using a differential thermal balance (TG-DTA, manufactured by Rigaku) with the temperature raised from room temperature (25°C) at a rate of 5°C per minute in the atmosphere. From Figure 14, the temperature when it reached 50% of the initial weight was about 400°C, and the temperature when it reached 20% of the initial weight was about 500°C. That is, it shows that if the substrate is heated at a temperature exceeding about 500°C, most of the substrate can be removed. Also, the thermal decomposition temperature of LCO was 510°C or higher.

[0146] Figure 15 is an image of the laminate after removing the substrate taken by an electron microscope. Figure 16 is an image of LCO heated under the same conditions as the above heating profile taken by an electron microscope. As shown in Figure 16, even when only LCO was heated, LCO did not have protrusions. On the other hand, as in Example 1, LCO was placed on the substrate, multiple substrates were laminated, and the LCO removed by heating had protrusions.

[0147] FIG. 17 is an image obtained by photographing a cross-section of the laminate after removing the substrate with an electron microscope. The cross-section sample was prepared using an ion milling device (manufactured by Leica). A plurality of protrusions 8 were deposited on the surface of the core portion 7 of LCO. In order to examine the composition of the protrusions 8, energy dispersive X-ray analysis (EDX) of a scanning electron microscope (SEM) or a transmission electron microscope (TEM) was performed. As a result, it was confirmed that the protrusions had the same Co and O peaks as the core portion. In addition, when a test piece obtained by solidifying the laminate after removing the substrate with resin and slicing it with FIB was observed with a cross-sectional TEM, a lattice-like texture corresponding to the crystal structure was observed in both the core portion and the protrusions. From the above, a positive electrode active material having protrusions deposited in a plurality of directions could be manufactured.

[0148] In addition, the cross-sections of the laminate before the heating step of removing the substrate (FIGS. 21(a) and (b)) and after the heating step of removing the substrate (FIGS. 21(c), (d), and (e)) were observed with a scanning electron microscope (SEM), respectively. As a result, a unique cross-sectional profile was observed in the cross-section of the laminate after the heating step of removing the substrate. Such a unique cross-sectional profile included the following features: <discontinuity inside the particles>, <core-shell-like gap structure 1>, <gap structure 2 between the core itself and the shell itself>, <protrusions observed in the outermost peripheral shell>, <dense regions and porous regions observed in each of the core and the shell>.

[0149] <discontinuity inside the particles> The cross-section of the particulate LCO visible in the SEM image of FIG. 21(b) shows a plane texture, whereas it can be read that the cross-section of the particulate LCO visible in the SEM images of FIGS. 21(d) and (e) shows a discontinuous texture inside the particles.

[0150] <core-shell-like gap structure 1> The cross-section of the particulate LCO in the SEM image of Fig. 21(b) shows a single-piece particle form, while the cross-sections of the particulate LCO in the SEM images of Figs. 21(d) and (e) show a core-shell structure with a core part C101 and a plurality of layered shell parts S111 and S121. That is, in the cross-sections of the particulate LCO in the SEM images of Figs. 21(d) and (e), a plurality of layered gaps LG111 and LG121 are observed along each shell part. The particle part of the positive electrode active material LCO is equivalently described as having a core part C101, shell parts S111 and S121, and layered gaps LG111 and LG121 located between such a core part and shell parts. In the particle part of the positive electrode active material LCO, it is equivalently described that a plurality of shell parts S111 and S121 and layered gaps LG111 and LG121 exist in the radial direction of the core part C101, respectively.

[0151] <Gap structure between the core itself and the shell itself 2> The cross-section of the particulate LCO in the SEM image of Fig. 21(b) shows a single-piece planar particle form as described above, while the cross-sections of the particulate LCO in the SEM images of Figs. 21(d) and (e) show radial gaps RG101 and RG111 extending in the directions of the core part C101 and the shell parts S111 and S121. The particle part of the positive electrode active material LCO has the radial gaps RG101 and RG111. Also, the particle part of the positive electrode active material LCO has a core part and a shell part, and it is equivalently described that the radial gaps exist at least in such a shell part S111.

[0152] <Protrusions observed on the outermost shell> From Fig. 21(e), protrusions P121 protruding outward are observed outside the outermost shell part S121. These protrusions P121 are considered to increase the contact probability between particulate positive electrode active materials LCO1000 or between a particulate positive electrode active material LCO1000 and an electrolyte (not shown).

[0153] The cross-section of the LCO particles contained in the laminate after the above heating process can be clearly read as having an increased specific surface area not only on the outer peripheral surface of the particles but also including the internal structure, compared to the LCO particles contained in the laminate before the heating process. The particle portion of the positive electrode active material LCO has a core portion C101 and shell portions S111, S121, and the protrusion P121 protrudes at least from the shell portion S121. There is also recognized a positive electrode active material LCO in which the protrusion protrudes from each of the shell portion and the core portion.

[0154] <Dense regions and porous regions recognized in each of the core and the shell> Such an increase in the specific surface area is presumed to be due to a part of the dense particles before heating being consumed in the radial growth of the shell portion and the core portion, crack generation, and growth of protrusions (whiskers). The core portion and the shell portion are considered to form a porous region by the generation of two types of gap structures, the increase in the diameter of the core portion and the shell portion, and the generation of protrusions. Similarly, it has been confirmed that the core portion C101 occurs in both the inner and outer directions in the radial direction of the core portion and the shell portion. It is considered that the portions not consumed by the generation of the two types of gap structures, the increase in the diameter of the core portion and the shell portion, and the generation of protrusions remain as dense regions extending in the circumferential direction. Also, the growth of the protrusions (whiskers) is considered to exhibit an effect of accelerating the gap formation action that separates the core portion and the shell portion, like icicles. Further, the diameter expansion action of the core-shell structure is considered to be realized by generating cracks in a metal oxide crystal with a low elastic modulus. Also, the generated cracks are considered to exhibit an effect of introducing oxygen contained in the firing atmosphere and a gas having a catalytic action into the layered gaps inside the particles.

[0155] (Example 2) An acrylic resin having adhesiveness (film thickness: 20 μm) was used as the second base material 11b. The coverage rate of the base material by LCO was 80%. Other conditions were the same as those in Example 1 to produce a positive electrode active material. As a result, a positive electrode active material having protrusions deposited in a plurality of directions could be produced in the same manner as in Example 1.

[0156] (Example 3) A lens array-shaped concavo-convex pattern was formed on the first substrate 11a. Different from Example 1, the lens array shape was a state in which lenses with a depth of 5.0 μm were arranged at a period of 12.0 μm. Also, different from Example 1, only the first particles were arranged on the substrate 11a without using the second particles (LCO). The coverage rate of the substrate by LCO was 60%. The positive electrode active material was produced under the same conditions as in Example 1 except for other conditions. As a result, a positive electrode active material having protrusions deposited in a plurality of directions could be produced in the same manner as in Example 1.

[0157] (Comparative Example 1) In the lamination unit U3, one substrate 11b on which a material layer was formed was attached onto an aluminum foil (thickness: 20 μm). The coverage rate of the substrate by LCO was 80%. The positive electrode active material was produced under the same conditions as in Example 1 except that the number of substrates to be laminated was changed to one. As a result, a positive electrode active material having protrusions deposited in a plurality of directions could not be produced.

[0158] [Manufacture of Positive Electrode] (Example 4) Using the above-described laminated manufacturing system 100, a positive electrode including a positive electrode active material having protrusions deposited in a plurality of directions was manufactured. Specifically, in the material layer forming unit U2, the material layer forming apparatus 1 shown in FIG. 2 was used. A material layer was formed on a substrate, and the substrate was removed by heating a laminate obtained by laminating the substrate on which the material layer was formed, thereby manufacturing a positive electrode.

[0159] As the first substrate 11a, a sheet made of polyethylene terephthalate (PET) was used. A lens array-shaped concavo-convex pattern was formed on the first substrate 11a by the pattern forming apparatus 23. This lens array shape was a state in which lenses with a depth of 5.5 μm were arranged at a period of 7.5 μm.

[0160] As the second base material 11b, a PET sheet with an acrylic adhesive applied to both the front surface (the surface on which the material layer is formed) and the back surface (the surface on which the material layer is not formed) was used. The thickness of the PET sheet was 5 μm, and the thickness of the acrylic adhesive applied to the front surface of the PET sheet was 1 μm.

[0161] As the first particles, the same LCO as in Example 1 was used. As the second particles, LBO (manufactured by Toyoshima Seisakusho), which is a solid electrolyte, was used. As the carrier materials S1 and S2, the same magnetic particles as in Example 1 were used. The volume-based cumulative 50% particle size of LBO was 5 μm. Thereby, the material layer 1 was formed. When forming the material layer 1, the ratio of LCO in the filler 241a was 17% by weight, and the ratio of LBO in the filler 241b was 15% by weight.

[0162] In the material layer 1, LCO and LBO were arranged on the base material, and the coverage rate of the base material by LCO and LBO was 80%. After forming the material layer on the base material, the base material was deelectrified using an electrostatic removal blower (manufactured by ASONE).

[0163] Next, in the lamination unit U3, the base material 11b with the material layer formed thereon was laminated in three layers on a separately prepared solid electrolyte sheet (thickness: 270 μm). The solid electrolyte sheet was produced by press-molding LAGP (manufactured by Toyoshima Seisakusho), which is a solid electrolyte, and sintering it in an electric furnace (850 °C / 12 h / air). Here, the volume-based cumulative 50% particle size of LAGP was 5 μm.

[0164] Thereafter, the solid electrolyte sheet with the base material 11b laminated thereon was placed in a laminate film (manufactured by Asahi Kasei Pax), subjected to vacuum lamination treatment using a vacuum packaging machine (manufactured by TOSEI), and pressurized at 200 MPa using an isostatic pressure pressurizing device (manufactured by Nikkiso). A laminate in which three base materials 11b with the material layer formed thereon were laminated on the solid electrolyte sheet was obtained.

[0165] Next, the base material was removed from the laminate by heating using the removal unit U4. As the removal unit U4, an electric furnace (a tabletop muffle furnace manufactured by Yamada Denki) was used. The laminate was placed on a ceramic stage inside the electric furnace and heated under no pressure and in the atmosphere. Using a heating profile, the temperature was raised from room temperature (25°C) to 250°C at a rate of 2.5°C per minute, then from 250°C to 510°C at a rate of 0.5°C per minute. After reaching 510°C, it was maintained for 1 hour and then cooled to room temperature (25°C). That is, it shows that most of the base material can be removed by heating the base material at a temperature exceeding about 500°C. Also, the thermal decomposition temperatures of LCO and LBO were both 510°C or higher. Thereby, a positive electrode including a positive electrode active material and a solid electrolyte was obtained.

[0166] Figure 18 is an image of the positive electrode surface of the positive electrode taken by an electron microscope. It was confirmed that the particle portion LBO10 of the electrolyte was filled in the gaps between the particle portions LCO9 of the positive electrode active material, and that it had protrusions LCO10 of the positive electrode active material precipitated in a plurality of directions from the particle portions LCO9 of the positive electrode active material. In other words, the particle portion LBO10 of the electrolyte was arranged between the particle portions of the particle portions LCO9 of the positive electrode active material.

[0167] To confirm the performance of the positive electrode as a battery, a battery was assembled. As the negative electrode, indium foil (thickness 50 μm) was fixed to the back surface (opposite side to the positive electrode surface) of the solid electrolyte sheet. As the positive electrode current collector, aluminum foil (thickness 10 μm) and as the negative electrode current collector, copper foil (thickness 10 μm) were fixed to the respective electrodes. A tab with a sealant was welded to the current collector, placed in an Al laminate film, subjected to vacuum lamination treatment with a vacuum packaging machine (manufactured by TOSEI), and pressurized with an isotropic pressure pressurizing device (manufactured by Nikkiso) to form an all-solid-state battery including a positive electrode, an electrolyte, and a negative electrode.

[0168] Figure 19 shows the results (Nyquist plot) of impedance measurement of the all-solid-state battery of Example 4. The horizontal axis Z’ of the Nyquist plot is the real axis of the impedance, and the vertical axis Z’’ is the imaginary axis of the impedance. The impedance measurement was performed using an electrochemical measurement device (manufactured by Solartron). A depressed semi-circle from a frequency of 1000 kHz to 10 kHz and a depressed semi-circle from a frequency of 1 kHz to 0.1 Hz were confirmed. The former semi-circle is the signal of the solid electrolyte, and the latter semi-circle is the resistance contributed by the electrode (mainly the electrode resistance). In Figure 19, LogZ from the electrode resistance Z (Ω) was 3. Here, the electrode resistance Z is a value calculated from the value of the diameter (Z’) of the latter semi-circle. The smaller the value of the electrode resistance, the easier it is for ions to move into the electrolyte.

[0169] Figure 20 shows the results of charge-discharge measurement (25 °C) of the all-solid-state battery of Example 4. The charge-discharge measurement was performed using a charge-discharge measurement system (manufactured by Biologic). The vertical axis is voltage (V), and the horizontal axis is the capacity (mAh) per gram of weight of LCO. The charge-discharge current (constant current) was 90 μA / cm 2 , the charge-discharge time was 2 hours, and the cut-off voltage was 3 V (lower limit) and 4.5 V (upper limit). At that time, the charge-discharge efficiency (the ratio of the discharge capacity to the charge capacity, %) was 94%. Here, the calculation method of the charge-discharge efficiency is a value obtained by dividing the discharge capacity at the end point in the discharge curve by the charge capacity at the end point in the charge curve. In Figure 20, the charge capacity at the end point of the charge curve was 107%, and the discharge capacity at the end point of the discharge curve was 100%.

[0170] (Comparative Example 2) In the laminated unit U3, one substrate 11b on which a material layer was formed was attached onto the solid electrolyte sheet. The coverage rate of the substrate by LCO and LBO was 80%. An anode electrode containing a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the anode electrode were produced in the same manner as in Example 4, except that the number of substrates to be laminated was changed to one.

[0171] (Example 5) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 300 °C, a positive electrode including a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode were produced in the same manner as in Example 4.

[0172] (Example 6) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 400 °C, a positive electrode including a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode were produced in the same manner as in Example 4.

[0173] (Example 7) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 600 °C, a positive electrode including a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode were produced in the same manner as in Example 4.

[0174] (Example 8) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 700 °C, a positive electrode including a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode were produced in the same manner as in Example 4.

[0175] (Example 9) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 800 °C, a positive electrode including a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode were produced in the same manner as in Example 4.

[0176] (Example 10) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 900 °C, a positive electrode including a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode were produced in the same manner as in Example 4.

[0177] (Example 11) As the removal unit U4, except that the reaching temperature of the heating profile of the electric furnace (tabletop muffle furnace manufactured by Yamada Denki) was changed from 510 °C to 1000 °C, in the same manner as in Example 4, a positive electrode electrode containing a positive electrode active material and a solid electrolyte, and an all-solid-state battery using the positive electrode electrode were fabricated.

[0178] 〔Evaluation method〕 · Protrusion: After performing the following impedance measurement and charge-discharge measurement, the all-solid-state battery was disassembled, the positive electrode was observed with an electron microscope, and the presence or absence of protrusions was confirmed. · Electrode resistance: The impedance of the all-solid-state battery was measured, and from the Nyquist plot, the order of the resistance contributed by the electrode (positive electrode) was determined. · Charge-discharge efficiency: The charge-discharge measurement of the all-solid-state battery was performed, and the charge-discharge efficiency was calculated from the obtained charge capacity and discharge capacity. The charge-discharge measurement was performed at a constant current, and the current amount per unit weight of the positive electrode active material was measured together.

[0179] The evaluation results are described in Table 1 below. In Table 1, the value LogZ obtained by taking the common logarithm with respect to the electrode resistance Z (Ω) is described.

[0180]

Table 1

[0181] In Comparative Example 2 where the positive electrode active material had no protrusions, the electrode resistance was high and charge / discharge could not be confirmed. On the other hand, in Examples 4 to 8 where the positive electrode active material had protrusions and the base material had sufficiently disappeared, charge / discharge was confirmed even at a high rate (equivalent to 0.5C). This is considered to be because inside the positive electrode, the positive electrode active material has protrusions and the solid electrolyte is filled around the positive electrode active material by the patterning device, so the interfacial area between the positive electrode active material and the solid electrolyte increases and the positive electrode resistance decreases. That is, it can be rephrased that the protrusions reduce the electrode resistance of the positive electrode by protruding in a plurality of directions from the particle portion so as to be related to the ionic conduction between the electrolyte and the particle portion. Further, by using an active material having a surface on which a plurality of particle portions are arranged as an electrode for a battery as in the present embodiment, the ionic conduction at the interface between the arranged surface and the electrolyte layer is promoted, and it is considered that the electrode resistance of the secondary battery decreases.

[0182] On the other hand, in Example 5 where the positive electrode active material had protrusions, the disappearance of the base material was insufficient and the positive electrode resistance did not decrease, so charge / discharge was not confirmed. Also, in Examples 10 and 11 where the positive electrode active material had protrusions, since they were heated at a high temperature, a reaction layer was formed at the interface between the positive electrode active material (LCO) and the solid electrolyte (LAGP, LBO), resulting in an increase in resistance, so charge / discharge was not confirmed.

[0183] In this example, the positive electrode was formed on a separately prepared solid electrolyte sheet, but it may also be formed on a current collector such as an aluminum foil or a stainless steel foil. In this case, the positive electrode (this molding) with a current collector and the negative electrode (indium) can be fixed to both sides of the solid electrolyte sheet, and the negative electrode current collector and the tab with a sealant can be put together into an Al laminate film to form an all-solid-state battery. Also, the electrolytes and negative electrodes other than the positive electrode may be formed by the same process. For example, a laminate in which a base material for the positive electrode and a base material for the negative electrode are laminated on both sides of a solid electrolyte sheet is formed, and the base material is removed by heating to obtain a molded body including a positive electrode, an electrolyte, and a negative electrode. Alternatively, a laminate in which a base material for the positive electrode and a base material for the electrolyte are laminated is formed, the base material is removed by heating, and a negative electrode (including indium, metallic lithium, etc.) formed by the same process or a different process is laminated to obtain a molded body including a positive electrode, an electrolyte, and a negative electrode. Alternatively, a laminate in which a base material for the positive electrode, a base material for the electrolyte, and a base material for the negative electrode are laminated is formed, and the base material is removed by heating to obtain a molded body including a positive electrode, an electrolyte, and a negative electrode.

[0184] In addition, other processes may be added to the above process to form the final all-solid-state battery. For example, after removing the base material by heating, the positive electrode may be filled with a solid electrolyte, a conductive assistant, or a binder resin. A solution is prepared by mixing at least one kind of particles of the above materials with a solvent, and the positive electrode is immersed in the solution so that the solution is filled. At this time, the positive electrode may contain only the positive electrode active material as in Examples 1 to 3 or may contain the positive electrode active material and the solid electrolyte as in Example 4. Also, an electrolyte containing a semi-solid material such as a polymer electrolyte sheet may be used in addition to the solid electrolyte sheet.

[0185] (Example 12) The positive electrode was manufactured using the above-described laminated shaping system 100 and applied to a lithium-ion battery using a liquid electrolyte. Specifically, three substrates on which a material layer (LCO) was formed were laminated on a current collector (aluminum foil 20 μm) in the same manner as in Example 1, and the positive electrode was manufactured by removing the substrates. The coverage rate of the substrate by LCO was 80%.

[0186] (Example 13) Using the above-described laminated manufacturing system 100, a positive electrode was manufactured and applied to a lithium-ion battery using a liquid electrolyte. Specifically, in the same manner as in Example 3, three substrates having a material layer (LCO) formed thereon were laminated on a current collector (aluminum foil 20 μm), and the positive electrode was manufactured by removing the substrates. The coverage rate of the substrate by LCO was 60%.

[0187] (Comparative Example 3) Using the above-described laminated manufacturing system 100, a positive electrode was manufactured and applied to a lithium-ion battery using a liquid electrolyte. Specifically, in the same manner as in Comparative Example 1, one substrate having a material layer (LCO) formed thereon was laminated on a current collector (aluminum foil 20 μm), and the positive electrode was manufactured by removing the substrate. The coverage rate of the substrate by LCO was 80%.

[0188] (Example 14) Using the above-described laminated manufacturing system 100, a positive electrode was manufactured and applied to a lithium-ion battery using a liquid electrolyte. Specifically, in the same manner as in Example 4, three substrates having a material layer (LCO + LBO) formed thereon were laminated on a current collector (aluminum foil 20 μm), and the positive electrode was manufactured by removing the substrates. The coverage rate of the substrate by LCO and LBO was 80%.

[0189] To confirm the performance of each electrode as a battery, the battery was assembled. The positive electrode, the separator, and the negative electrode sheet (graphite) were laminated and pressed in a coin case, and the coin battery was assembled by filling it with an electrolytic solution. Note that as the negative electrode sheet, a sheet obtained by coating a solvent containing graphite, a binder resin, etc. on a current collector by a coating process, drying, and pressing was used, but metal lithium formed by a vapor deposition process or the like may also be used. Further, in the same process as the positive electrode, a material obtained by forming a negative electrode active material such as graphite or LTO on a current collector may be used.

[0190] 〔Evaluation method〕 · Protrusion: After the following impedance measurement and charge-discharge measurement, the lithium-ion battery was disassembled, the positive electrode was observed with an electron microscope, and the presence or absence of protrusions was confirmed. · Rate: The charge-discharge measurement of the lithium-ion battery was performed, and the rate at which the charge-discharge efficiency satisfies 80% or more (1C: the current amount that charges and discharges in 1 hour with respect to the actual capacity of the positive electrode active material).

[0191] The evaluation results are described in Table 2 below.

[0192]

Table 2

[0193] For Comparative Example 3 in which the positive electrode active material did not have protrusions, the rate characteristics of Examples 12 to 14 in which the positive electrode active material had protrusions were improved. This is considered to be because inside the positive electrode, the positive electrode active material had protrusions, the interfacial area of the filled liquid electrolyte increased, and the positive electrode resistance decreased.

[0194] (Example 15) Using the above-described laminated shaping system 100, the LCO of Example 1 manufactured was used as a raw material, a positive electrode was formed, and it was applied to a lithium-ion battery using a liquid electrolyte. The method of forming the positive electrode will be described. The manufactured positive electrode active material was sufficiently stirred and mixed with a binder resin, a conductive assistant, and a solvent, and then coated on a current collector (aluminum foil). The positive electrode active material may be pretreated such as classification, pulverization treatment, or surface treatment before stirring and mixing. The current collector was dried and pressurized to form a positive electrode. The assembly of the battery is the same as in Example 4.

[0195] (Comparative Example 4) Using LCO on which protrusions did not precipitate as a raw material, a positive electrode was formed in the same manner as in Example 4 and applied to a lithium-ion battery using a liquid electrolyte.

[0196] 〔Evaluation Method〕 · Protrusion: After the following impedance measurement and charge-discharge measurement, the lithium-ion battery was disassembled, the positive electrode was observed with an electron microscope, and the presence or absence of protrusions was confirmed. · Rate: Perform charge and discharge measurements of the lithium-ion battery, and the rate (1C: the current amount that completes charging and discharging in 1 hour with respect to the actual capacity of the positive electrode active material) that satisfies a charge and discharge efficiency of 80% or more.

[0197] The evaluation results are described in Table 3 below.

[0198]

Table 3

[0199] The rate characteristics of Example 15 in which the positive electrode active material has protrusions were improved compared to Comparative Example 4 in which the positive electrode active material does not have protrusions. This is presumably because inside the positive electrode, the positive electrode active material has protrusions, the interfacial area of the filled liquid electrolyte increases, and the positive electrode resistance (electrode resistance) decreases.

Claims

1. An active material applied to a secondary battery together with an electrolyte, comprising lithium cobaltate, having a particle portion including a core portion and a plurality of layered shell portions located outside the core portion via a plurality of layered gap portions, and a protruding portion protruding from the shell portion in a plurality of directions.

2. The active material according to claim 1, wherein the particle portion has a discontinuous texture including a layered gap structure in a cross section within the particle.

3. The active material according to claim 1 or 2, wherein the protruding portion has a structure protruding from the shell portion in at least one of the forms of frost column, whisker, needle, fold, dendrite.

4. The active material according to any one of claims 1 to 3, wherein a plurality of the shell portions and the layered gaps are alternately present in the radial direction of the core portion.

5. The active material according to any one of claims 1 to 4, wherein the particle portion has a radial gap in the inner shell portion of the plurality of layered shell portions.

6. The active material according to any one of claims 1 to 5, wherein the protruding portion protrudes in both the inner and outer directions of the shell portion.

7. The active material according to any one of claims 1 to 6, wherein the active material is a positive electrode active material.

8. The active material according to any one of claims 1 to 7, wherein the protruding portion contains Co and O and exhibits a lattice-like texture corresponding to a crystal structure in a cross-sectional TEM image.

9. A positive electrode applied to a secondary battery, The positive electrode comprising a plurality of the active materials according to any one of claims 1 to 8, having a surface on which a plurality of the particle portions are arranged.

10. The positive electrode according to claim 9, further comprising an electrolyte disposed between the plurality of particle portions.

11. The positive electrode according to claim 10, wherein the protruding portion protrudes from the particle portion in a plurality of directions so as to be related to ion conduction between the electrolyte and the particle portion.

12. A secondary battery comprising the positive electrode according to any one of claims 9 to 11, An electrolyte layer containing an electrolyte and arranged to form an interface with the positive electrode, A negative electrode containing a negative electrode active material.

13. A method for manufacturing an active material applied to a secondary battery together with an electrolyte and having protruding portions deposited in a plurality of directions, A method for manufacturing an active material, comprising: a first step of forming a material layer by disposing particulate lithium cobaltate having a softening point temperature higher than the thermal decomposition temperature of the resin substrate on the resin substrate; a second step of forming a laminate by laminating a plurality of the material layers; and a third step of firing the laminate at a temperature higher than the thermal decomposition temperature in an atmosphere containing oxygen gas to sinter the lithium cobaltate, thereby depositing protrusions in a plurality of directions from the particulate lithium cobaltate.

14. The method for manufacturing an active material according to claim 13, wherein the heating temperature in the third step is 400°C or higher and 800°C or lower.

15. The method for manufacturing an active material according to claim 13 or 14, further comprising a charge removal step between the first step and the second step.

16. The method for manufacturing an active material according to any one of claims 13 to 15, further comprising a pressing step between the second step and the third step.

17. The method for manufacturing an active material according to claim 16, wherein the pressing step is performed by vacuum degassing.

18. The method for manufacturing an active material according to claim 16 or 17, wherein the pressing step is performed by isostatic pressing.

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