JP2015109250A - Electrode, method and device for manufacturing electrode, and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode capable of minimizing loss of battery capacity while improving ion conductivity at a part close to a collector, even when the thickness of an active material layer is increased.SOLUTION: In an electrode (3), a plurality of holes (25, 26) is holed in a surface direction of active material layers (5, 6) formed with a predetermined thickness on a collector (4). In the electrode, the number of active material particles existing per unit volume on sides (5A, 6A) close to the collector (4) of the active material layers (5, 6) is relatively small, while the number of active material particles existing per unit volume on sides (5B, 6B) apart from the collector (4) is relatively large.

Description

  The present invention relates to an electrode, an electrode manufacturing method, a manufacturing apparatus, and a battery.

  In order to improve the ionic conductivity of an electrode, there is one in which a plurality of holes in the thickness direction are formed in an active material layer by laser processing (see Patent Document 1).

Japanese Patent No. 3690522

  By the way, when the thickness of the active material layer is increased in order to increase the discharge capacity of the battery, the number of active material particles present per unit volume on the side closer to the current collector is smaller than the side away from the current collector. The amount of electrolyte increases, and the electrolyte does not easily penetrate. For this reason, there is a problem that ions hardly move on the side close to the current collector. In this case, by making a hole in the thickness direction of the active material layer as in Patent Document 1 above, ions can travel back and forth near the current collector, and ion conductivity on the side closer to the current collector. Is improved. However, drilling a hole in the active material layer means that the volume of the active material layer is reduced by the amount of drilling the hole, resulting in a loss of discharge capacity. There is a limit to improving the ion conductivity on the side close to the current collector only by drilling the hole.

  Therefore, an object of the present invention is to provide an electrode that can suppress the loss of battery capacity while improving the ionic conductivity near the current collector even if the thickness of the active material layer is increased.

  An electrode according to an aspect of the present invention is an electrode in which a plurality of holes in the thickness direction are formed in the surface direction of the active material layer, and is configured as follows. That is, the number of active material particles present per unit volume on the side close to the current collector in the active material layer is relatively small, and the active material particles present per unit volume on the side away from the current collector To be relatively large.

  According to an aspect of the present invention, the number of active material particles present per unit volume on the side close to the current collector in the active material layer is relatively small, and the number per unit volume exists on the side away from the current collector. There are relatively many active material particles. For this reason, ions are particularly active on the side closer to the current collector than when the number of active material particles present per unit volume on the side closer to the current collector is larger than the side away from the current collector. It becomes easy to move in the surface direction. Thereby, even if the thickness of the active material layer is increased, the loss of battery capacity can be suppressed while improving the ion conductivity, particularly in the surface direction, of the active material layer near the current collector.

FIG. 1 is a schematic cross-sectional view of a power generation element according to a first embodiment of the present invention. FIG. 2A is an enlarged model diagram of a portion corresponding to the broken line portion shown in FIG. 1 in a known power generation element. FIG. 2B is an enlarged model diagram of the broken line portion shown in FIG. 3A is an enlarged model diagram of a portion corresponding to the broken line portion shown in FIG. 1 in the power generation element of Reference Example 1. FIG. FIG. 3B is an enlarged model diagram of the broken line portion shown in FIG. FIG. 4 is a partially enlarged cross-sectional view of the power generation element of the second embodiment. FIG. 5 is a schematic cross-sectional view of the power generation element of the third embodiment. FIG. 6 is an enlarged model diagram of a broken line portion shown in FIG. FIG. 7 is an enlarged model diagram of a broken line portion shown in FIG. FIG. 8 is a front view of the electrode manufacturing apparatus according to the fourth embodiment. FIG. 9 is a front view of the electrode manufacturing apparatus of the fourth embodiment. FIG. 10A is a view for explaining the first active material layer forming step of the fifth embodiment. FIG. 10B is a view for explaining the second active material layer forming step of the fifth embodiment. FIG. 10C is a view for explaining the plastic working process of the fifth embodiment. FIG. 11A is a view for explaining the first active material layer forming step of the fifth embodiment. FIG. 11B is a view for explaining the second active material layer forming step of the fifth embodiment. FIG. 11C is a view for explaining the plastic working process of the fifth embodiment. FIG. 12A is a view for explaining a transfer sheet creating process of the sixth embodiment. FIG. 12B is a view for explaining the first transfer seal pasting step of the sixth embodiment. FIG. 12C is a view for explaining the second transfer seal pasting step of the sixth embodiment. FIG. 12D is a view for explaining the plastic working process of the sixth embodiment. FIG. 13A is a diagram for explaining a transfer sheet creating process according to the sixth embodiment. FIG. 13B is a view for explaining the first transfer seal pasting step of the sixth embodiment. FIG. 13C is a view for explaining the second transfer seal attaching step of the sixth embodiment. FIG. 13D is a view for explaining the plastic working process of the sixth embodiment. FIG. 14A is a view for explaining a transfer seal creating process of the seventh embodiment. FIG. 14B is a view for explaining the first transfer seal pasting step of the seventh embodiment. FIG. 14C is a view for explaining the second transfer seal pasting step of the seventh embodiment. FIG. 14D is a view for explaining a plastic working process according to the seventh embodiment. FIG. 15A is a view for explaining a transfer seal creating process of the seventh embodiment. FIG. 15B is a view for explaining the first transfer seal pasting step of the seventh embodiment. FIG. 15C is a view for explaining the second transfer seal pasting step of the seventh embodiment. FIG. 15D is a view for explaining the plastic working process of the seventh embodiment. FIG. 16 is a characteristic diagram of the discharge performance of Comparative Examples 1 and 2. FIG. 17 is a characteristic diagram of the discharge performance of Comparative Example 2 and Example 1. FIG. 18A is an enlarged model diagram of a portion corresponding to the broken line portion shown in FIG. 1 in the power generation element of the eighth embodiment. FIG. 18B is an enlarged model diagram of the broken line portion shown in FIG. FIG. 19 is a characteristic diagram of the discharge performance of the power generating element according to the ninth embodiment. FIG. 20 is an enlarged model diagram of a portion corresponding to the broken line portion shown in FIG. 1 in the power generation element of the ninth embodiment. FIG. 21 is an enlarged model diagram of a portion corresponding to the broken line portion shown in FIG. 1 in the power generation element of the tenth embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the dimension ratio of drawing has the location exaggerated on account of description, and the location differs from the actual ratio.

(First embodiment)
The lithium ion secondary battery 1 has a structure in which a substantially square flat power generation element 2 in which a charge / discharge reaction actually proceeds is sealed inside a laminate film that is a battery outer package in a state of being immersed in an electrolytic solution. Have. FIG. 1 is a schematic longitudinal sectional view of a power generation element 2 according to a first embodiment of the present invention, and FIG. 2 is an enlarged model view of a broken line portion shown in FIG.

  In FIG. 1, the power generation element 2 has a structure in which a negative electrode 3, a separator 13, and a positive electrode 8 are laminated in this order. FIG. 1 shows only two negative electrodes, one positive electrode, and two separators. Here, the negative electrode 3 of the electrodes is obtained by disposing negative electrode active material layers 5 and 6 on both surfaces (surfaces) of a rectangular thin plate-shaped negative electrode current collector 4. Similarly, the positive electrode 8 is obtained by arranging positive electrode active material layers 10 and 11 on both surfaces (surfaces) of a positive electrode current collector 9 having a rectangular thin plate shape. The separator 13 is mainly formed from a porous thermoplastic resin. The electrolytic solution travels to the positive electrode side and the negative electrode side through the porous holes. Thereby, the adjacent negative electrode 3, the separator 13, and the positive electrode 8 constitute one unit cell layer 15 (unit cell). In the single battery layer 15, electrons and ions move between the two electrodes to perform a charge / discharge reaction of the battery.

  Now, in the lithium ion secondary battery, the battery performance can be improved by improving the ionic conductivity in the electrodes 3 and 8. In order to improve the ionic conductivity in the electrode, it is important to improve the ionic conductivity in both the <1> electrode thickness direction and the <2> electrode surface direction in the electrode. Here, the “electrode thickness direction” is the stacking direction of the electrodes 3 and 8 (vertical direction in FIG. 1). On the other hand, since the electrodes 3 and 8 are square thin plate-shaped, they have a plane. The “electrode surface direction” is a direction along this plane. Hereinafter, in the present invention, ionic conductivity on the side close to the current collector is particularly targeted.

  There is a method of forming an active material layer by applying an active material slurry from a die coater onto a current collector in a predetermined thickness to form a coating film, and then heating and drying the coating film. When the active material layer is made thicker by using this method in order to increase the discharge capacity of the battery, there is a problem that the ion conductivity of the active material layer becomes worse on the side closer to the current collector.

  This is due to the following reason. That is, the active material particles are uniformly present in the coating film immediately after the coating film is formed on the current collector by applying the active material slurry to the current collector. At this time, the active material particles are floating in the solvent. However, since gravity acts on each active material particle floating in the solvent, each active material particle may precipitate in the solvent (fall down vertically) as time elapses. Thereby, in the coating film, the number of active material particles present per unit volume is relatively low on the vertical upper side, and the number of active material particles existing per unit volume is relatively low on the vertical lower side. Become more. And when the coating film changes into an active material layer by heating and drying, the number of active material particles present per unit volume is relatively smaller in the vertical direction on the inside of the active material layer, The number of active material particles present per unit volume is relatively large. The portion where the solvent evaporates remains as a space. The electrolytic solution fills the space where the solvent evaporates and ions move in the electrolytic solution. Here, the case where the electrolyte is liquid will be described, but the electrolyte may be in a gel form. The ease of movement of ions is related to the number of active material particles present per unit volume. The greater the number of active material particles present per unit volume, the more difficult it is for the electrolyte to penetrate into the space where the solvent evaporates and the ions remain less likely to move in the plane direction of the active material layer (active material layer The ionic conductivity in the surface direction of the is deteriorated). That is, when the thickness of the active material layer is thin, the uneven distribution of the active material particles in the vertical direction does not matter so much, but when the thickness of the active material layer is increased, the uneven distribution of the active material particles in the vertical direction is not. It becomes large and it may be difficult for ions to move near the current collector.

  For this reason, there is Reference Example 1 in which a plurality of cylindrical holes are formed in the surface direction of the electrodes 3 and 8. When the holes are drilled in the thickness direction of the electrodes 3 and 8, the holes are filled with the electrolyte solution, and ions can freely move back and forth within the holes, and ion conductivity is improved on the side of the holes closer to the current collector. . However, on the other hand, drilling holes in the electrodes 3 and 8 means that the volume of the active material layer is reduced by the volume of one hole × the number of holes, resulting in a loss of discharge capacity. . This is because the electric capacity of the battery is proportional to the volume of the electrode (specifically, the volume of the active material layer), and thus forming a large number of holes causes capacity loss.

  Therefore, in the first embodiment of the present invention, an electrode having a plurality of holes in the thickness direction formed in the active material layer is configured as follows. That is, the number of active material particles present per unit volume on the side close to the current collector in the active material layer is relatively small, and the active material particles present per unit volume on the side away from the current collector To be relatively large. Specifically, the active material layer formed on one side of the current collector is formed by stacking at least two split active material layers in the thickness direction, and the split active material on the side closer to the current collector of each split active material layer. The number of active material particles present per unit volume is made smaller in the material layer. For example, when an active material layer formed on one side of the current collector by stacking two divided active material layers in the thickness direction, the divided active material on the side closer to the current collector among the divided active material layers is formed. The number of active material particles present per unit volume is smaller in the material layer than in the divided active material layer on the side farther from the current collector.

  Specifically, the negative electrode 3 will be described. As shown in FIG. 2B, the negative electrode active material layer 5 formed on one side of the negative electrode current collector 4 is divided into the divided negative electrode actives on the side close to the negative electrode current collector 4. The material layer 5A and the divided active material layer 5B on the side away from the negative electrode current collector 4 are stacked in the thickness direction. The thicknesses of the divided negative electrode active material layers 5A and 5B are set to the same predetermined value h1. Further, the negative electrode active material layer 6 formed on the other side of the negative electrode current collector 4 is divided into a divided negative electrode active material layer 6A on the side close to the negative electrode current collector 4 and a divided active material layer on the side away from the negative electrode current collector 4. 6B is stacked in the thickness direction. The thicknesses of the divided negative electrode active material layers 6A and 6B are set to the same predetermined value h1. Hereinafter, the divided negative electrode active material layers 5A and 6A on the side closer to the negative electrode current collector 4 are referred to as “first divided negative electrode active material layers”, and the divided active material layers 5B and 6B on the side away from the negative electrode current collector 4 are referred to as “second This is referred to as a “divided negative electrode active material layer”.

  The first divided negative electrode active material layers 5A and 6A are configured so that the number of active material particles present per unit volume is relatively small (the active material particles are relatively sparse). In the second divided negative electrode active material layers 5B and 6B, the number of active material particles present per unit volume is relatively large (the active material particles are relatively dense). Here, for simplicity, it is assumed that the active materials contained in the four divided negative electrode active material layers 5A, 6A, 5B, and 6B exist in the form of particles and all have the same diameter.

  Further, in order to allow lithium ions in the electrolytic solution to reach the first divided negative electrode active material layers 5A and 6A at an early stage, cylindrical holes 25 that reach the first divided negative electrode active material layers 5A and 6A in the thickness direction, A plurality of holes 26 are formed in the surface direction of the negative electrode active material layers 5 and 6. Here, the cylindrical holes 25 and 26 are aligned with the same diameter and the same depth in any one of the plane directions of the negative electrode active material layers 5 and 6 and in a direction orthogonal to the arbitrary one direction. Suppose you are. Each of the holes 25 and 26 is constituted by cylindrical side surfaces 25A and 26A and circular bottom surfaces 25B and 26B (see FIG. 2B).

  The same applies to the positive electrode. That is, as shown in FIG. 1, the positive electrode active material layer 10 formed on one side of the positive electrode current collector 9 is divided from the divided positive electrode active material layer 10 </ b> A on the side close to the positive electrode current collector 9 and the positive electrode current collector 10. A layered structure in which the separated positive electrode active material layer 10 </ b> B on the far side is overlapped in the thickness direction. The thicknesses of the divided positive electrode active material layers 10A and 10B are set to the same predetermined value h2. In addition, the positive electrode active material layer 11 formed on the other side of the positive electrode current collector 9 is divided into a divided positive electrode active material layer 11A on the side closer to the positive electrode current collector 10 and a divided active material layer on the side away from the positive electrode current collector 10. 11B is stacked in the thickness direction. The thicknesses of the divided positive electrode active material layers 11A and 11B are set to the same predetermined value h2. The predetermined value h2 may be the same as the predetermined value h1. Hereinafter, the divided positive electrode active material layer closer to the positive electrode current collector 10 is referred to as “first divided positive electrode active material layer”, and the divided positive electrode active material layer away from the positive electrode current collector 10 is referred to as “second divided positive electrode active material layer”. "

  The first divided positive electrode active material layers 10A and 11A are configured such that the number of active material particles present per unit volume is relatively small (the active material particles are relatively sparse). In the second divided positive electrode active material layers 10B and 11B, the number of active material particles present per unit volume is relatively large (the active material particles are relatively dense). Here, for the sake of simplicity, it is assumed that many active materials contained in each of the divided positive electrode active material layers 10A, 11A, 10B, and 11B exist in the form of particles and all have the same diameter.

  Moreover, in order to make the ions in the electrolyte reach the first divided positive electrode active material layers 10A and 11A at an early stage, cylindrical holes 27 and 28 that reach the first divided positive electrode active material layers 10A and 11A in the thickness direction. Are formed in the surface direction of the positive electrode active material layers 10 and 11. Here, the cylindrical holes 27 and 28 are aligned with the same diameter and the same depth in any one of the plane directions of the positive electrode active material layers 10 and 11 and in a direction orthogonal to the arbitrary one direction. Suppose you are. Each of the holes 27 and 28 includes cylindrical side surfaces 27A and 28A and circular bottom surfaces 27B and 28B.

  In addition, the shape of said holes 25-28 is not restricted to a column shape. For example, a plurality of holes having the same shape and the same depth, such as a regular triangular prism shape, a regular quadrangular prism shape, a regular hexagonal column shape, a regular octagonal column shape, and an elliptical column shape may be formed in the surface direction of the active material layer.

  In addition, the hole diameter of each hole 25-28 drilled in the active material layer of 1st Embodiment and the space | interval (pitch) of two holes adjacent to a rolling direction are defined as follows. That is, the hole diameter of each hole 25-28 is 100 micrometers or less. The reason why the hole diameter of each of the holes 25 to 28 is set to 100 μm or less is to prevent the volume of the active material layer (electrode) from being reduced by forming each of the holes 25 to 28. Since the electric capacity of the battery is proportional to the volume of the electrode (specifically, the volume of the active material layer), if a large hole is formed, capacity loss occurs. This capacity loss can be reduced by setting the diameters of the holes 25 to 28 to 100 μm or less.

  The distance (pitch) between two holes adjacent in the surface direction of the active material layer is 200 μm or less. This is because the distance that enables effective ion conduction in the electrode is approximately 100 μm based on the knowledge of the inventors so far. Therefore, the effect of improving ion conductivity in the surface direction can be exhibited by setting the pitch of the holes 25 to 28 in the surface direction of the active material layer to 200 μm (one side 100 μm) or less.

  For comparison with the present embodiment, the case of Reference Example 1 is shown in FIG. When the thickness of the coating is increased, the number of active material particles present per unit volume on the side away from the current collector is relatively small, and the active material present per unit volume on the side closer to the current collector It has been mentioned above that the number of particles can be relatively large. In Reference Example 1, by increasing the thickness of the coating film formed on the current collector, the number of active material particles present per unit volume is relatively small on the side away from the current collector, and The number of active material particles present per unit volume on the side closer to the electric body is relatively large. Therefore, as shown in FIG. 2A, as Reference Example 1, the positions of the first divided negative electrode active material layers 5A and 6A and the second divided negative electrode active material layers 5B and 6B are opposite to those in the first embodiment. Can be thought of as The second divided negative electrode active material layers 5B, 6B are on the side closer to the negative electrode current collector 4, and the first divided negative electrode active material layers 5A, 6A are on the side away from the negative electrode current collector 4, This means that the number of active material particles is relatively small on the side away from the surface, and the number of active material particles is relatively large on the side close to the current collector 4.

3A is a model diagram for explaining the movement of lithium ions in the case of Reference Example 1, and FIG. 3B is a model for explaining the movement of lithium ions in the case of this embodiment. FIG. In the case of Reference Example 1, as shown in FIG. 3 (A), the lithium ions in the electrolytic solution pass through holes 25 and 26, and the second divided negative electrode active material layer that is present near the negative electrode current collector 4 Reach 5B and 6B early. However, in the second divided negative electrode active material layers 5B and 6B, since the number of active material particles present per unit volume is relatively large, the electrolyte solution is difficult to permeate, and even if the electrolyte solution permeates, the electrolyte solution The passage is narrow.
Therefore, in the second divided negative electrode active material layers 5B and 6B, lithium ions are less likely to move in the thickness direction of the active material layers 5 and 6 and in the plane direction of the active material layers 5 and 6 (the active material layers 5 and 6). The ion conductivity in the thickness direction and in the plane direction is deteriorated).

  On the other hand, in this embodiment, as shown in FIG. 3B, the lithium ions in the electrolytic solution pass through the holes 25 and 26 and the first divided negative electrode active that exists near the negative electrode current collector 4. The material layers 5A and 6A are reached early. In the first divided negative electrode active material layers 5A and 6A, since the number of active material particles present per unit volume is relatively small, the electrolyte solution penetrates well and the passage of the electrolyte solution is wide. Therefore, in the first divided negative electrode active material layers 5A and 6A, lithium ions easily move in the thickness direction of the active material layers 5 and 6 and the surface direction of the active material layers 5 and 6 (the active material layers 5 and 6 The ionic conductivity in the thickness direction and in the plane direction is improved).

  Thus, the electrode of this embodiment is an electrode in which a plurality of holes 25, 26, 27, and 28 are formed in the surface direction of the active material layers 5, 6, 10, and 11, and is as follows. Configure. That is, the number of active material particles present per unit volume on the side closer to the current collectors 4 and 9 (5A, 6A, 10A, and 11A) of the active material layers 5, 6, 10, and 11 is relatively reduced. Like that. On the side away from the current collectors 4 and 9 (5B, 6B, 10B, and 11B), the active material particles present per unit volume are relatively increased.

  Therefore, the active material layers 5 and 6 are closer to the current collectors 4 and 9 than the case of the reference example 1 where the number of active material particles present per unit volume is relatively large on the side closer to the current collector 4. The electrolyte solution permeates well on the sides (5A, 6A, 10A, 11A), and ions easily move particularly in the plane direction of the active material layer. Thereby, even if the thickness of the active material layers 5, 6, 10, and 11 is increased, the ion conductivity in the surface direction of the active material layers 5, 6, 10, and 11 on the side close to the current collectors 4 and 9 is increased. The battery capacity loss can be suppressed while improving the above.

  In the present embodiment, the active material layers 5, 6, 10, and 11 are divided into first divided active material layers 5A, 6A, 10A, and 11A and second divided active material layers 5B, 6B, 10B, and 11B (at least two active materials). Layer) in the thickness direction. The first divided active material layers 5A, 6A, 10A, and 11A are more than the second divided active material layers 5B, 6B, 10B, and 11B (the active material layers closer to the current collector among the active material layers). The number of active material particles present per unit volume is small. Thus, the first divided active material layers 5A, 6A, 10A, and 11A closer to the current collectors 4 and 9 are closer to the second divided active material layers 5B, 6B, and 10B closer to the current collectors 4 and 9. , 11B facilitates the movement of ions in the thickness direction and the surface direction of the active material layers 5, 6, 10, and 11.

  In the present embodiment, since the holes 25 to 28 reach the vicinity of the current collectors 4 and 9, ions can be moved to the vicinity of the current collectors 4 and 9 through the holes 25 to 28 at an early stage.

(Second Embodiment)
FIG. 4 is a partially enlarged cross-sectional view of the power generation element 2 of the second embodiment. The same parts as those in FIG. 2B of the first embodiment are denoted by the same reference numerals.

  In the first embodiment, each active material layer formed on one side and the other side of the current collector is configured by stacking at least two divided active material layers in the thickness direction, and the current collector of each divided active material layer The number of active material particles present per unit volume is reduced in the divided active material layer closer to the side. On the other hand, in the second embodiment, each active material layer formed on one side and the other side of the current collector has an active material that exists per unit volume as it approaches the current collector in the thickness direction of the active material layer (electrode). The number of particles is continuously reduced.

  In addition, since it is difficult to represent that the number of active material particles present per unit volume continuously decreases as the current collector is closer to the thickness direction in the drawing, FIG. 4 represents a general image. Yes. That is, the negative electrode active material layer 5 formed on one side of the current collector is formed by stacking five divided negative electrode active material layers 5C to 5G in the thickness direction, and is close to the negative electrode current collector 4 in each divided active material layer. The number of active material particles present per unit volume is reduced in the divided active material layer on the side. Similarly, the negative electrode active material layer 6 formed on the other side of the current collector is formed by stacking five divided negative electrode active material layers 6C to 6G in the thickness direction, and among the divided active material layers, the negative electrode current collector The divided active material layer closer to 4 has a smaller number of active material particles per unit volume.

  And by increasing the number of the divided negative electrode active material layers with reference to FIG. 4, the number of active material particles present per unit volume continuously increases as the negative electrode current collector 4 is approached in the thickness direction. We approach the negative electrode active material layer, which decreases.

  The same applies to the positive electrode. That is, as the positive electrode active material layer 10 formed on one side of the positive electrode current collector 9 approaches the negative electrode current collector 9 in the thickness direction of the positive electrode active material layer 10, the number of active material particles present per unit volume increases. To be less. The number of active material particles present per unit volume increases as the positive electrode active material layer 11 formed on the other side of the positive electrode current collector 9 approaches the positive electrode current collector 9 in the thickness direction of the positive electrode active material layer 11. To be less.

  In the second embodiment, in order to form the active material layers 5, 6, 10, and 11 in which the number of active material particles present per unit volume continuously decreases as the current collectors 4 and 9 are approached in the thickness direction. May be performed by spray coating to be described later.

  The active material layer is formed by stacking at least two divided active material layers in the thickness direction, and the divided active material layer closer to the current collector of each divided active material layer is the active material particle present per unit volume. When the number decreases, the possibility that peeling occurs between adjacent layers cannot be denied. On the other hand, in the second embodiment, the number of active material particles present per unit volume is continuously reduced as the active material layers 5 and 6 are closer to the current collector 4 than the side opposite to the current collector 4. ing. In the second embodiment, there is no space between layers. As a result, the active material layer is formed by stacking at least two divided active material layers in the thickness direction, and the divided active material layer closer to the current collector among the divided active material layers is present per unit volume. Compared with the case where the number of substance particles is reduced, the occurrence of peeling between adjacent layers can be suppressed.

(Third embodiment)
FIG. 5 is a schematic longitudinal sectional view of the power generation element 2 of the third embodiment, and FIG. 6 is an enlarged model diagram of the broken line portion shown in FIG. The same parts as those in FIGS. 1 and 2 of the first embodiment are denoted by the same reference numerals.

  In the first embodiment, in order to cause ions in the electrolytic solution to reach the first divided active material layers 5A, 6A, 10A, and 11A at an early stage, the first divided active material layers 5A, 6A, Holes 25 to 28 reaching 10A and 11A were made. On the other hand, in the third embodiment, as shown in FIGS. 5 and 6, each hole 25 provided in the negative electrode active material layer 5 is drilled through the negative electrode current collector 4 in the thickness direction of the active material layers 5 and 6. It is set. Further, each hole 26 provided in the negative electrode active material layer 6 is formed by penetrating the negative electrode current collector 4 in the thickness direction of the active material layers 5 and 6.

  The same applies to the positive electrode 8. That is, as shown in FIG. 5, each hole 27 provided in the positive electrode active material layer 10 is formed by penetrating the positive electrode current collector 9 in the thickness direction of the active material layers 10 and 11. Further, each hole 28 provided in the negative electrode active material layer 11 is formed by penetrating the positive electrode current collector 9 in the thickness direction of the active material layers 5 and 6.

  FIG. 7 is a model diagram for explaining the movement of lithium ions in the case of the third embodiment. In the third embodiment, as shown in FIG. 7, not only the first divided negative electrode active material layer in which the lithium ions in the electrolyte pass through the holes 25 and 26 but before the current collector 4, but also the current collector 4. The first divided negative electrode active material layer beyond this is also reached early. Therefore, lithium ions easily move in the thickness direction and the surface direction of the negative electrode active material layers 5 and 6 in the first divided negative electrode active material layers 5A and 6A on both sides of the negative electrode current collector 4 (negative electrode active material layer). The ion conductivity in the thickness direction and the surface direction of 5 and 6 is improved).

  As described above, in the third embodiment, since the holes 25 to 28 penetrate the current collectors 4 and 9, the active material layers 5, 6, 10, and 11 are located near both surfaces of the current collectors 4 and 9. The movement of ions in the thickness direction and the surface direction can be facilitated.

(Fourth embodiment)
In the embodiments from the fourth embodiment to the seventh embodiment, a method for manufacturing the electrodes 3 and 8 described in the first embodiment will be mainly described. First, FIGS. 8 and 9 are front views of the electrode manufacturing apparatus of the fourth embodiment. Here, the manufacturing method of the negative electrode 3 will be described in particular. In the fourth embodiment, an active material layer forming step # 1, a heating / drying step # 2, and a plastic working step # 3 are included as a method for producing one negative electrode active material layer 5 of the negative electrode 3.

  First, in the active material layer forming step # 1 (not shown), a negative electrode active material slurry is applied to one surface of the negative electrode current collector 4 to form a coating film. More specifically, the negative electrode active material slurry is guided to a die coater from a tank containing a negative electrode active material slurry (not shown). Then, the negative electrode active material slurry is discharged from the die coater onto the tape-like negative electrode current collector 4 moving at a constant speed, thereby forming a coating film having a predetermined thickness on the negative electrode current collector 4. The negative electrode active material slurry is obtained by crushing a lump of a negative electrode active material with a mill to form negative electrode active material particles having a uniform diameter, and dispersing and dissolving the active material particles having a uniform diameter in a suitable solvent. is there. An active material slurry may contain a conductive additive or a binder.

  In the next heating / drying step # 2, the above-mentioned coating film is heated and dried to form the negative electrode active material layer 5. However, in the fourth embodiment, even if the thickness of the negative electrode active material layer 5 is increased, the number of active material particles present per unit volume inside the negative electrode active material layer 5 formed after heating and drying. Is uniform in the vertical direction.

  In the next plastic working step # 3, as shown in FIG. 8, the negative electrode current collector 4 in which the negative electrode active material slurry is applied on one side, heated and dried to form the negative electrode active material 5, is formed on the base 21. The active material layer 5 is placed on top and moved between the roller 22 as a mold. On the outer periphery of the roller 22, a large number of cylindrical convex portions 23 (processed portions) shorter than the thickness of the negative electrode active material layer 5 are provided in the rotation direction of the roller 22 and the axial direction of the roller 22. By pressing the convex portion 23 of the roller 22 onto the negative electrode active material layer 5 in one direction from above, cylindrical holes 25 are formed at equal intervals in the surface direction of the negative electrode active material layer 5 with respect to the negative electrode active material layer 5. .

  When the negative electrode active material layer 5 is pressed (pressurized), the pressed active material portion is plastically deformed. Therefore, the number of active material particles present per unit volume is within the pressed active material portion. More than the active material part that is not pressed. Here, the pressed active material portion is on the side away from the negative electrode current collector to form a layer having a predetermined thickness, and the unpressed active material portion is on the side close to the negative electrode current collector and is also predetermined. A layer of thickness is formed. That is, by pressing, the pressed active material portion corresponds to the second divided negative electrode active material layer 5B, and the unpressed active material portion corresponds to the first divided negative electrode active material layer 5A. Here, the first divided negative electrode active material layer 5 </ b> A and the second divided are assumed by pressing so that the pressed active material portion has a half thickness and the unpressed active material portion has the remaining half thickness. The negative electrode active material layer 5B is shown in a portion surrounded by a one-dot chain line in FIG.

  By drilling columnar holes 25 in the negative electrode active material layer 5, each hole 25 is composed of a cylindrical side surface 25A and a circular bottom surface 25b. Since the convex portion 23 of the roller 22 is shorter than the thickness of the negative electrode active material layer 5, the bottom surface 25 b of the hole 25 does not reach the negative electrode current collector 4 as shown in FIG.

  Next, in the fourth embodiment, an active material layer forming step # 11, a heating / drying step # 12, and a plastic working step # 13 are included as a manufacturing method of the other negative electrode active material layer 6 of the negative electrode 3.

  First, the active material layer forming step # 11 is the same as the above active material layer forming step # 1. That is, in the active material layer forming step # 11, the negative electrode active material slurry is applied to the remaining one surface of the negative electrode current collector 4 to form a coating film.

  In the next heating / drying step # 12, the negative electrode active material layer 6 is formed by heating and drying the coating film. However, in the fourth embodiment, even if the thickness of the negative electrode active material layer 6 is increased, the number of active material particles present per unit volume inside the negative electrode active material layer 6 formed after heating and drying. Is uniform in the vertical direction.

  In the next plastic working step # 13, as shown in FIG. 9, the negative electrode current collector 4 in which the negative electrode active material slurry is applied to the remaining one surface, heated and dried to form the negative electrode active material layer 6, The negative electrode active material layer 6 is placed on the top and moved between the rollers 22 again. At this time, since the negative electrode active material layers 5 and 6 are respectively formed on both surfaces of the negative electrode current collector 4, the thickness of the negative electrode is different from the previous time. Therefore, the distance between the base 21 and the center of the roller 22 is adjusted so that a cylindrical hole 27 is formed in the negative electrode active material layer 6 with the same hole depth as that of the negative electrode active material layer 5 on the opposite side. . As a result, a large number of cylindrical holes 26 are also formed in the negative electrode active material layer 6 in the rotation direction of the roller 22 and the axial direction of the roller 22 (see FIG. 1).

  When the negative electrode active material layer 6 is pressed (pressurized), the pressed active material portion is plastically deformed. Therefore, the number of active material particles present per unit volume is within the pressed active material portion. More than the active material part that is not pressed. Here, the pressed active material portion is on the side away from the negative electrode current collector to form a layer having a predetermined thickness, and the unpressed active material portion is on the side close to the negative electrode current collector and is also predetermined. A layer of thickness is formed. That is, by pressing, the pressed active material portion corresponds to the second divided negative electrode active material layer 6B, and the unpressed active material portion corresponds to the first divided negative electrode active material layer 6A. Here, the first divided negative electrode active material layer 6A and the second divided are assumed to have a half thickness of the pressed active material portion and a remaining half thickness of the unpressed active material portion by pressing. The negative electrode active material layer 6B is shown in a portion surrounded by a one-dot chain line in FIG.

  By drilling columnar holes 25 in the negative electrode active material layer 5, each hole 25 is composed of a cylindrical side surface 25A and a circular bottom surface 25b. Each hole 26 formed in the negative electrode active material layer 6 is also composed of a cylindrical side surface 26 </ b> A and a circular bottom surface 26 b, and the bottom surface of each hole 26 does not reach the negative electrode current collector 4.

  This completes the hole processing for each of the active material layers 5 and 6 for the negative electrode 3. Next, the positive electrode 8 is similarly processed to form cylindrical holes 27 and 28 in the respective active material layers 10 and 11 (FIG. 1).

  Even when the positive electrode active material layers 10 and 11 are pressed (pressurized), the pressed active material portion is plastically deformed, so that the active material particles existing per unit volume inside the pressed active material portion. Is greater than the active material portion that is not pressed. Here, the pressed active material portion is on the side away from the positive electrode current collector to form a layer having a predetermined thickness, and the unpressed active material portion is on the side close to the positive electrode current collector and is also predetermined A layer of thickness is formed. That is, by pressing, the pressed active material portion corresponds to the second divided negative electrode active material layers 10B and 11B, and the unpressed active material portion corresponds to the first divided negative electrode active material layers 10A and 11A. .

  In this way, each of the four active material layers 5, 6, 10, 11 has two divided active material layers 5A, 5B, 6A, 6B, 10A, 10B, each having a different number of active material particles per unit volume. 11A and 11B. Then, when the two electrodes 3 and 8 in which the respective cylindrical holes 25 to 28 are formed in each of the active material layers 5, 6, 10, and 11 are stacked via the separator 13, the result is as shown in FIG. And the holes 25 to 28 are filled with the electrolytic solution.

  8 and 9 show the case where the holes 25 and 26 do not penetrate the negative electrode current collector 4, but when the holes 25 and 26 penetrate the negative electrode current collector 4, they are shown in FIG. In addition, the electrodes 3 and 8 of the third embodiment are obtained.

  In the fourth embodiment, the plastic working steps # 3 and # 13 exist per unit volume of the active material portion plastically deformed by rolling in one direction with a roller (die) 22 having a convex portion 23 on the surface. This is a step of drilling a plurality of holes 25 to 28 in the active material layers 5, 6, 10, and 11 while increasing the number of active material particles to be performed as compared with the active material portions that are not plastically deformed. According to the fourth embodiment, due to plastic deformation of the active material portion rolled by the roller 22, the remaining active material portions in which the number of active material particles present per unit volume of the plastically deformed active material portion is not plastically deformed. Become more. As a result, the number of active material particles present per unit volume on the side closer to the current collector 4 (5A, 6A) in the active material layers 5 and 6 is relatively small, and the side away from the current collector 4 (5B 6B), the active material particles present per unit volume can be relatively increased.

(Fifth embodiment)
10 and 11 are front views for explaining the manufacturing method of the negative electrode 3 of the fifth embodiment. In the fourth embodiment shown in FIGS. 8 and 9, the active material slurry is applied to one surface of the current collector to form a coating film, and this coating film is heated and dried to form the active material layer. On the other hand, 5th Embodiment forms an active material layer by the spray coating by the spray coater 31. FIG. Here, the spray coater 31 sends the active material slurry contained in the tank 32 to the nozzle 34 by the pump 33 and injects it from the nozzle 34 toward the current collector in the form of a mist.

  Here, in particular, a method for manufacturing the negative electrode 3 will be described. In the fifth embodiment, as a method for producing one negative electrode active material layer 5 of the negative electrode 3, an active material slurry adjustment step # 21, a first active material layer formation step # 22, a second active material layer formation step # 23, heating A drying step # 24 and a plastic working step # 25 are included.

  First, in the active material slurry adjustment step # 21 (not shown), the number of active material particles of the negative electrode active material mixed in a certain amount of solvent is made different, and the number of active material particles mixed in a certain amount of solvent is relatively small. The negative electrode active material slurry and the negative electrode active material slurry having a relatively large number of active material particles mixed in a certain amount of solvent are prepared. In this case, the diameters of the mixed active material particles are all the same. Hereinafter, the negative electrode active material slurry in which the number of active material particles mixed in a certain amount of solvent is relatively reduced is referred to as “first negative electrode active material slurry”. The negative electrode active material slurry in which the number of active material particles mixed in a certain amount of solvent is relatively increased is referred to as “second negative electrode active material slurry”.

  In the next first active material layer forming step # 22, as shown in FIG. 10 (A), a coating film having a thickness of a predetermined value h1 by spray coating with a spray coater 31 (this coating film is referred to as “first coating layer”). A coating film "). At this time, the first negative electrode active material slurry is used as the negative electrode active material slurry. After the first coating layer is dried to some extent after the completion of the first active material layer forming step # 22, the second active material layer forming step # 23 is performed.

  In the second active material layer forming step # 23, as shown in FIG. 10B, a coating film having a thickness of a predetermined value h1 (this coating film) is formed on the first coating film to some extent by spray coating. The film is referred to as a “second coating film”. At this time, the second negative electrode active material slurry is used as the negative electrode active material slurry.

  In the next heating / drying step # 24, the first and second applied coatings are heated and dried. By heating and drying, the first coating on the side close to the negative electrode current collector 4 is applied to the first divided negative electrode active material layer 5A, and the second coating on the side away from the negative electrode current collector 4 is applied to the second divided negative electrode active material. It becomes layer 5B.

  In the next plastic working step # 25, as shown in FIG. 10C, a plurality of holes 25 are formed in the negative electrode active material layer 5 by drilling (machining).

  Next, in the fifth embodiment, as a method for producing the other negative electrode active material layer 5 of the negative electrode 3, an active material slurry adjustment step # 31, a first active material layer formation step # 32, and a second active material layer formation step # are performed. 33, heating / drying step # 34, and plastic working step # 35 are included.

  First, the active material slurry adjustment step # 31 (not shown) is the same as the active material slurry adjustment step # 21. By using the first negative electrode active material slurry and the second negative electrode active material slurry adjusted in the active material slurry adjustment step # 21 as they are, the active material slurry adjustment step # 31 can be omitted.

  In the next first active material layer forming step # 32, as shown in FIG. 11 (A), a coating film having a thickness of a predetermined value h1 by spray coating with a spray coater 31 (this coating film is referred to as “first coating layer”). A coating film "). At this time, the first negative electrode active material slurry is used as the negative electrode active material slurry. After the first coating layer is dried to some extent after the first active material layer forming step # 32, the second active material layer forming step # 32 is performed.

  In the second active material layer forming step # 32, as shown in FIG. 11B, a paint film having a thickness of a predetermined value h1 is formed on the first paint film that is dried to some extent by spray coating (this coating The film is referred to as a “second coating film”. At this time, the second negative electrode active material slurry is used as the negative electrode active material slurry.

  In the next heating / drying step # 34, the two first and second coated films are heated and dried. By heating and drying, the first coating on the side close to the negative electrode current collector 2 is applied to the first divided negative electrode active material layer 6A, and the second coating on the side away from the negative electrode current collector 4 is applied to the second divided negative electrode active material. It becomes layer 6B.

  In the next plastic working step # 35, as shown in FIG. 11C, a plurality of holes 26 are formed in the negative electrode active material layer 6 by drilling (machining).

  The positive electrode 8 is also manufactured in the same manner as shown in FIGS.

  Even when a coating film is formed by spray coating, gravity acts on the active material particles flowing in the coating film as described above. For this reason, each active material particle may precipitate in the solvent (falling vertically downward) over time. Accordingly, the number of active material particles present per unit volume on the vertically lower side is relatively increased, and the number of active material particles existing per unit volume on the vertically upper side is relatively decreased. And when the coating film changes into an active material layer by heating and drying, the number of active material particles present per unit volume is relatively small inside the active material layer, and The number of active material particles present per unit volume is relatively large. The uneven distribution of the active material particles in the vertical direction increases as the thickness of the coating film applied at a time increases. On the other hand, in the fifth embodiment, the first coating film is first formed with half the desired thickness, and after the first coating film has dried to some extent, the second coating film with half the desired thickness is formed. Is forming. If the thickness of the coating film formed at one time is half of the desired thickness, the uneven distribution of the active material particles in the vertical direction is half that when the thickness of the coating film formed at one time is the desired thickness. It will be over. For this reason, the uneven distribution of the active material particles in the vertical direction within each divided negative electrode active material layer 5A, 6A, 5B, 6B does not become a problem. Furthermore, when the first and second coating films are formed with a thickness of ½ of the desired thickness, if the uneven distribution of the active material particles in the vertical direction becomes a problem, the desired thickness It is only necessary to form three coating films with a thickness of 1/3. This is because the uneven distribution of the active material particles in the vertical direction decreases as the thickness decreases. In other words, the thickness that allows the uneven distribution of the active material particles in the vertical direction is obtained in advance as the reference thickness Dstd, and the desired thickness Dtgt is divided by the reference thickness Dstd to be divided and overcoated. The number of layers to be obtained is obtained. If the quotient is not divisible, only one is divided and the number of layers to be overcoated is increased. In the fifth embodiment, the case where the first and second coating films are overcoated has been described. However, the present invention is not limited to this.

  In the fifth embodiment, the active material layer forming process is the following process. That is, a plurality of first and second negative electrode active material slurries (active material slurries with different numbers of active material particles present per unit volume) are prepared, and the negative electrode active material slurries are sprayed on the current collector 4 in order. Processes # 22, # 23, # 32, and # 33. And after the 1st coating film formed by spraying the 1st negative electrode active material slurry (the previous active material slurry in the said order) dries, the 2nd negative electrode active material slurry (the following active material slurry in the said order) Is sprayed to form a second coating film. Further, the first coating film is made closer to the current collector 4 than the second coating film (the coating film of the active material slurry having a smaller number of active material particles per unit volume). Accordingly, the number of active material particles present per unit volume is relatively small on the side of the active material layer close to the current collector (5A, 6A), and the side of the active material layer that is far from the current collector (6A 6B), the active material particles present per unit volume can be relatively increased.

(Sixth embodiment)
12 and 13 are front views for explaining the manufacturing method of the negative electrode 3 of the sixth embodiment. In the sixth embodiment, an active material layer is formed by attaching a transfer seal to a current collector.

  Here, in particular, a method for manufacturing the negative electrode 3 will be described. In the sixth embodiment, as a method for producing one negative electrode active material layer 5 of the negative electrode 3, a transfer seal creating step # 41, a first transfer seal attaching step # 42, a second transfer seal attaching step # 43, plastic working Step # 44 is included.

  First, in the transfer sheet creation step # 41, as shown in FIG. 12A, the transfer seal 41 having the first divided negative electrode active material layer 5A having a thickness h1 on the transfer sheet 43 is created. . Further, the transfer seal 42 having the second divided negative electrode active material layer 5B having a thickness h1 is formed on the transfer sheet 44.

Here, the first divided negative electrode active material layer 5A formed on the transfer sheet 43 is formed as follows. That is, a coating film having a predetermined value h1 (this coating film is referred to as “first coating film”) is formed by spray coating using a spray coater or coating using a die coater.
At this time, the first negative electrode active material slurry is used as the negative electrode active material slurry. Next, the first coating film is heated and dried. By heating and drying, the first coating film becomes the first divided negative electrode active material layer 5A. Further, the second divided negative electrode active material layer 5B formed on the transfer sheet 44 is formed as follows. That is, a coating film having a thickness of the predetermined value h1 (this coating film is referred to as “second coating film”) is formed by spray coating using a spray coater or coating using a die coater. At this time, the second negative electrode active material slurry is used as the negative electrode active material slurry. Next, the second coating film is heated and dried. By heating and drying, the second coating film becomes the second divided negative electrode active material layer 5B. Hereinafter, the transfer seal in which the first divided negative electrode active material layer 5A is formed on the transfer sheet 43 is referred to as “first transfer seal”, and the transfer seal in which the second divided negative electrode active material layer 5B is formed on the transfer sheet 44 is “ This is called “second transfer seal”.

  In the next first transfer seal pasting step # 42, as shown in FIG. 12B, the first divided negative electrode active material 5A side of the first transfer seal 41 is pressed against the negative electrode current collector 4. Thus, after the first divided negative electrode active material layer 5A is attached onto the negative electrode current collector 4, the transfer sheet 43 is peeled off.

  In the next second transfer seal pasting step # 43, as shown in FIG. 12C, the second divided negative electrode active material layer 5B side of the second transfer seal 42 is placed on the first divided negative electrode active material layer 5A. Press on. Thus, after the second divided negative electrode active material layer 5B is attached on the first divided negative electrode active material layer 5A, the transfer sheet 44 is peeled off.

  In the next plastic working step # 44, as shown in FIG. 12D, a plurality of holes 25 are formed in the negative electrode active material layer 5 by drilling.

  Next, in the sixth embodiment, as a method for producing the other negative electrode active material layer 5 of the negative electrode 3, a transfer seal creating step # 51, a first transfer seal attaching step # 52, and a second transfer seal attaching step # 53. Then, plastic working step # 54 is included.

  First, in the transfer sheet creating step # 51, as shown in FIG. 13A, the transfer seal 51 having the first divided negative electrode active material layer 6A having the thickness h1 is formed on the transfer sheet 43. . Further, the transfer seal 52 having the second divided negative electrode active material layer 6B having a thickness h1 is formed on the transfer sheet 44.

  Here, the first divided negative electrode active material layer 6A formed on the transfer sheet 43 is formed as follows. That is, a coating film having a predetermined value h1 (this coating film is referred to as “first coating film”) is formed by spray coating using a spray coater or coating using a die coater. At this time, the first negative electrode active material slurry is used as the negative electrode active material slurry. Next, the first coating film is heated and dried. By heating and drying, the first coating film becomes the first divided negative electrode active material layer 6A. Further, the second divided negative electrode active material layer 6B formed on the transfer sheet 44 is formed as follows. That is, a coating film having a thickness of the predetermined value h1 (this coating film is referred to as “second coating film”) is formed by spray coating using a spray coater or coating using a die coater. At this time, the second negative electrode active material slurry is used as the negative electrode active material slurry. Next, the second coating film is heated and dried. By heating and drying, the second coating film becomes the second divided negative electrode active material layer 6B. Hereinafter, the transfer seal in which the first divided negative electrode active material layer 6A is formed on the transfer sheet 43 is referred to as “first transfer seal”, and the transfer seal in which the second divided negative electrode active material layer 6B is formed on the transfer sheet 44 is “ This is called “second transfer seal”.

  In the next first transfer seal sticking step # 52, as shown in FIG. 13B, the first divided negative electrode active material layer 6A side of the first transfer seal 51 is pressed against the negative electrode current collector 4. Thus, after the first divided negative electrode active material layer 6A is attached to the negative electrode current collector 4, the transfer sheet 43 is peeled off.

  In the next second transfer seal attaching step # 53, as shown in FIG. 13C, the second divided negative electrode active material layer 6B side of the second transfer seal 52 is placed on the first divided negative electrode active material layer 6A. Press on. As a result, the second divided negative electrode active material layer 6B is pasted on the first divided negative electrode active material layer 6A, and then the transfer sheet 44 is peeled off.

  In the next plastic working step # 54, as shown in FIG. 13D, a plurality of holes 26 are formed in the negative electrode active material layer 6 by drilling.

  The positive electrode 8 is also manufactured in the same manner as shown in FIGS.

  Even when a coating film is formed on the transfer sheets 43 and 44 by spray coating, or when a coating film is formed on the transfer sheets 43 and 44 by a die coater, as described above, Gravity acts on material particles. For this reason, each active material particle may precipitate in the solvent (falling vertically downward) over time. As a result, the number of active material particles present per unit volume on the side closer to the transfer sheets 43 and 44 is relatively large, and the number of active material particles present per unit volume on the side away from the transfer sheets 43 and 44. Is relatively less. And when the coating film changes into an active material layer by heating and drying, the number of active material particles present per unit volume is relatively smaller in the vertical direction on the inside of the active material layer, The number of active material particles present per unit volume is relatively large. The uneven distribution of the active material particles in the vertical direction increases as the thickness of the coating film applied at a time increases. On the other hand, in the sixth embodiment, the first and second coating films are formed on the transfer sheets 43 and 44 at half the desired thickness. If the thickness of the coating film formed at one time is half of the desired thickness, the uneven distribution of the active material particles in the vertical direction is half that when the thickness of the coating film formed at one time is the desired thickness. It will be over. For this reason, the uneven distribution of the active material particles in the vertical direction within each divided negative electrode active material layer 5A, 6A, 5B, 6B does not become a problem. Further, if the first and second coating films are formed on the transfer sheet with a thickness that is ½ of the desired thickness, if uneven distribution of the active material particles in the vertical direction becomes a problem. A coating film may be formed on each of the three transfer sheets with a thickness of 1/3 of the desired thickness. At this time, there are three transfer seals. This is because the uneven distribution of the active material particles in the vertical direction decreases as the thickness decreases. In other words, the thickness of the active material particles that can allow uneven distribution in the vertical direction is obtained in advance as the reference thickness Dstd, and the transfer seal to be divided by dividing the desired thickness Dtgt by the reference thickness Dstd. The number of is obtained. If the quotient is not divisible, the number of transfer seals to be divided by one is increased. In the sixth embodiment, the case where the transfer seals are the first and second transfer seals has been described. However, the present invention is not limited to this.

  In the sixth embodiment, the active material layer forming process is a transfer seal attaching process # 42, # 44, # 52, # 54. In the above transfer seal pasting steps # 42, # 44, # 52, and # 54, at least two sheets of transfer in which active material layers having different numbers of active material particles present per unit volume are formed on a transfer sheet. Seals 41, 42, 51 and 52 are used. Then, the smaller the number of active material particles present per unit volume of the active material layer of the transfer seal, the closer to the current collector side. As a result, the number of active material particles present per unit volume in the first divided negative electrode active material layers 5A and 6A (on the active material layer side closer to the current collector) can be relatively reduced. The active material particles present per unit volume can be relatively increased in the second divided negative electrode active material layers 5B and 6B (on the side of the active material layer away from the current collector).

(Seventh embodiment)
14 and 15 are front views for explaining the manufacturing method of the negative electrode 3 of the seventh embodiment. The same parts as those in FIGS. 12 and 13 of the sixth embodiment are denoted by the same reference numerals. The seventh embodiment also forms an active material layer by attaching a transfer seal, but the transfer seal creation step # 41 is different from the sixth embodiment.

  Here, in particular, a method for manufacturing the negative electrode 3 will be described. In the seventh embodiment, as a method for producing one negative electrode active material layer 5 of the negative electrode, transfer seal creating step # 41, first transfer seal attaching step # 42, second transfer seal attaching step # 43, plastic working step # 44 is included.

  In the seventh embodiment, the transfer seal creating process # 41 further includes a first transfer seal creating process # 61, a third transfer seal creating process # 62, and a pressurizing process # 63.

  First, in the first transfer seal creating step # 61, a transfer seal 41 (first transfer seal) having the first divided negative electrode active material layer 5A having a thickness h1 is formed on the transfer sheet 43. In the third transfer seal creating step # 62, the transfer seal 41 (having the first divided negative electrode active material layer 5A on the transfer sheet 43 with a predetermined thickness h1 ′ (h1 ′> h1) larger than the predetermined value h1. This transfer seal is referred to as a “third transfer seal”).

  In the next pressurizing step # 63, the third transfer seal 41 'is pressed in the thickness direction. Thus, the thickness of the third transfer seal 41 'is reduced from the predetermined value h1' to the predetermined value h1 (plastically deformed). In the first divided negative electrode active material layer 5A of the third point transfer seal 41 ′ plastically deformed by press working, the number of active material particles present per unit volume increases from before the plastic deformation, and adjacent active material particles The distance between them becomes shorter. Thus, the plastically deformed first divided negative electrode active material layer 5A is formed from a negative electrode active material slurry (that is, a second negative electrode active material slurry) in which the number of active material particles mixed in a certain amount of solvent is relatively increased. This is equivalent to the second divided negative electrode active material layer 5B. As a result, the first divided negative electrode active material layer 5A whose thickness is compressed to a predetermined value h1 by pressing can be handled as the second divided negative electrode active material layer 5B. In other words, it is the thickness of the first divided negative electrode active material layer 5A of the third transfer seal 41 ′ so that the first divided negative electrode active material layer after press working can be identified with the second divided negative electrode active material layer 5B. The predetermined value h1 ′ is determined in advance.

  As described above, the third transfer seal creation process # 62 and the pressurization process # 63 are different from the transfer seal creation process # 41 of the sixth embodiment, and the subsequent processes # 42, # 43, and # 44 are the sixth implementation. It is the same as the form.

  Next, in the seventh embodiment, as a method for producing the other negative electrode active material layer 6 of the negative electrode 3, a transfer seal creating step # 51, a first transfer seal attaching step # 52, and a second transfer seal attaching step # 53. Then, plastic working step # 54 is included.

  In the seventh embodiment, the transfer seal creating process # 51 further includes a first transfer seal creating process # 71, a third transfer seal creating process # 72, and a pressurizing process # 73.

  First, in the first transfer seal creating step # 71, a transfer seal 51 (first transfer seal) having the first divided negative electrode active material layer 6A having a thickness h1 on the transfer sheet 43 is created. In the third transfer seal creating step # 72, the transfer seal 51 (having the first divided negative electrode active material layer 6A having a predetermined value h1 ′ (h1 ′> h1) greater than the predetermined value h1 on the transfer sheet 43 is provided. This transfer seal is referred to as a “third transfer seal”).

  In the next pressurizing step # 73, the third transfer seal 51 'is pressed in the thickness direction. As a result, the thickness of the third transfer seal 51 'is reduced from the predetermined value h1' to the predetermined value h1 (plastically deformed). In the first divided negative electrode active material layer 6A of the third point transfer seal 51 ′ plastically deformed by press working, the number of active material particles present per unit volume increases from before the plastic deformation, so that adjacent active material particles The distance between them becomes shorter. Thus, the plastically deformed first divided negative electrode active material layer 6A is formed from a negative electrode active material slurry (that is, a second negative electrode active material slurry) in which the number of active material particles mixed in a certain amount of solvent is relatively increased. This is equivalent to the second divided negative electrode active material layer 6B. As a result, the first divided negative electrode active material layer 6A whose thickness is compressed to a predetermined value h1 by pressing can be handled as the second divided negative electrode active material layer 6B. In other words, it is the thickness of the first divided negative electrode active material layer 6A of the third transfer seal 51 ′ so that the first divided negative electrode active material layer after press working can be identified with the second divided negative electrode active material layer 6B. The predetermined value h1 ′ is determined in advance.

  As described above, the third transfer seal creation process # 72 and the pressurization process # 73 are different from the transfer seal creation process # 51 of the sixth embodiment, and the subsequent processes # 52, # 53, and # 54 are the sixth implementation. It is the same as the form.

  In the seventh embodiment, the active material layer forming step # 41 includes first transfer seal creation steps # 61 and # 71, third transfer seal creation steps # 62 and # 72, pressurization steps # 63 and # 73, and pasting. Steps # 42, # 43, # 52, and # 53 are included. In the first transfer seal creation steps # 61 and # 71 described above, a first active material layer having a predetermined thickness (h1) having a relatively small number of active material particles per unit volume on a transfer sheet. Transfer seals 41 and 51 are created. In the third transfer seal creation steps # 62 and # 72, the active material layer having a relatively small number of active material particles per unit volume on the transfer sheet is thicker than the predetermined thickness (h1). Third transfer seals 41 ′ and 51 ′ having a thickness (h1 ′) are formed. In the above pressurization steps # 63 and # 73, the active material layer of the third transfer seal is plastically deformed by pressing the third transfer seals 41 ′ and 51 ′ in the thickness direction, and the unit volume after the plastic deformation. The number of active material particles present per unit is made larger than that of the first transfer seals 41 and 51. In the pasting steps # 42, # 43, # 52 and # 53, the third transfer seals 42 and 52 and the first transfer seals 41 and 51 after plastic deformation by the pressurizing step are arranged in this order on the current collectors 4 and 9. Paste to. Thereby, even from only one type of active material slurry, two divided active material layers 5A, 5B, 6A, and 6B having relatively different numbers of active material particles per unit volume can be easily formed.

(Comparative Example 1)
A battery (coin cell) using the negative electrode 3 and the positive electrode 8 in which no hole was formed in the active material layer was manufactured as Comparative Example 1. The negative electrode active material layer of Comparative Example 1 was formed only from the second divided negative electrode active material layer, and the positive electrode active material layer of Comparative Example 1 was formed from only the second divided positive electrode active material layer.

(Comparative Example 2)
After forming the active material layer in the same manner as in Comparative Example 1, negative electrode 3 and positive electrode 8 having holes formed in the active material layer were prepared, and a battery using this negative electrode 3 and positive electrode 8 was produced as Comparative Example 2. .

Example 1
A plurality of holes are formed in the active material layer, and the number of active material particles present per unit volume continuously decreases as the current collectors 4 and 9 are approached in the thickness direction of the active material layer (electrode). Negative electrode 3 and positive electrode 8 were prepared. A battery using the negative electrode 3 and the positive electrode 8 was produced as Example 1. In this case, the most distant from the negative electrode current collector in the negative electrode active material layer is almost the same as the composition of the second divided negative electrode active material layer, and the most from the positive electrode current collector in the positive electrode active material layer. It is made to become substantially equal to the composition of the second divided positive electrode active material layer on the remote side.

(Evaluation)
FIGS. 16 and 17 are characteristic diagrams of the discharge performance of Comparative Examples 1 and 2 and Example 1 in which the discharge capacity at a predetermined rate is measured and summarized. According to FIGS. 16 and 17, the discharge capacity in Example 1 can be increased as compared with Comparative Example 2.

(Eighth embodiment)
FIG. 18A is a model diagram for explaining the movement of lithium ions in the present embodiment. FIG. 18B is a model diagram for explaining the movement of lithium ions in the case of the first embodiment. 18A and 18B show only the negative electrode current collector 4, the first divided active material layer 5A, and the second divided active material layer 5B, but the positive electrode current collector plate. The same applies to the first divided active material layer 6A and the second divided active material layer 6A.

  Whereas the hole 25 of the first embodiment is drilled in a direction (thickness direction) perpendicular to the negative electrode current collector 4, the hole 25 of the present embodiment has a thickness of the negative electrode current collector 4. It is inclined with respect to the vertical direction.

  In the case of the first embodiment, since the hole 25 is formed in the thickness direction of the negative electrode current collector plate 4, the lithium ions passing through the hole 25 hardly collide with the side surface 25A, and the first divided active material layer 5A. Reaches the surface of the negative electrode current collector plate 4 and diffuses into the first divided active material layer 5A.

  On the other hand, in the present embodiment, since the hole 25 is inclined with respect to the thickness direction of the negative electrode current collector plate 4, a part of the lithium ions toward the negative electrode current collector 4 collide with the side surface 25 </ b> A of the hole 25. To do. The lithium ions colliding with the side surface 25A flow out from the hole 25 to the first divided active material layer 5A or the second divided active material layer 5B and diffuse. Note that there are also lithium ions that move to the end of the hole 25 on the negative electrode current collector plate 4 side without colliding with the side surface 25 </ b> A and move from there to the surface direction of the negative electrode current collector plate 4.

  Comparing the path length (ion conduction distance) of the lithium ions existing near the negative electrode current collector plate 4 from the entrance of the hole 25 to the current position, the direction after reaching the vicinity of the negative electrode current collector plate 4 The configuration of this embodiment that diffuses into the active material layer from the middle of the hole 25 is shorter than the configuration of the first embodiment that performs conversion. That is, the configuration of the present embodiment has higher ion conductivity than the configuration of the first embodiment.

  FIG. 19 is a characteristic diagram of the discharge performance of the battery including the electrode of the present embodiment, the above-described comparative example 2, and the above-described example 1, which are collected by measuring the discharge capacity at a predetermined rate. As shown in FIG. 19, according to the present embodiment, the discharge capacity can be further increased as compared with Example 1.

  In the above description, the negative electrode 3 has been described, but the same applies to the positive electrode 8.

  As described above, in the present embodiment, the plurality of holes 25 and 26 provided in the active material layers 5 and 6 are formed so as to be inclined with respect to the thickness direction of the current collector plates 4 and 9. Thereby, compared with the case where the holes 25 and 26 are drilled so as to be orthogonal to the surface direction of the current collector plates 4 and 9, the ion conduction distance until the lithium ions diffuse near the current collector plates 4 and 9 is shorter. And ionic conductivity is increased.

(Ninth embodiment)
FIG. 20 is a model diagram for explaining how lithium ions move in the present embodiment. FIG. 20 shows only the negative electrode current collector 4, the first divided active material layer 5A, and the second divided active material layer 5B, but the positive electrode current collector plate 9 and the first divided active material layer 6A. The same applies to the second divided active material layer 6A.

  Whereas the hole 25 of the first embodiment is drilled in the thickness direction of the negative electrode current collector 4, the hole 25 of the present embodiment has a negative electrode current collector in a portion that penetrates the second divided active material layer 5B. The portion extending in the thickness direction of the electric plate 4 and penetrating the first divided active material layer 5 </ b> A is inclined with respect to the direction orthogonal to the surface direction of the negative electrode current collector 4.

  In the second divided active material layer 5B, since the active material particles are denser than the first divided active material layer 5A, lithium ions are less likely to be conducted. Therefore, in the portion that penetrates the second divided active material layer 5B, the hole 25 is inclined with respect to the thickness direction of the negative electrode current collector plate 4 in comparison with the portion that penetrates the first divided active material layer 5A. The effect of improving the ionic conductivity by flowing lithium ions out of the second divided active material layer 5B is small.

  Therefore, the portion that penetrates the second divided active material layer 5B is in the thickness direction of the negative electrode current collector plate 4, and the portion that penetrates the first divided active material layer 5A is orthogonal to the surface direction of the negative electrode current collector plate 4. It is set as the hole 25 inclined with respect to the direction to do. With such a configuration, lithium ions quickly reach the first divided active material layer 5A without almost flowing out from the hole 25 to the second divided active material layer 5B in the portion that penetrates the second divided active material layer 5B. And flows out from the side surface 25A of the hole 25 to the first divided active material layer 5A. The effect of improving ion conductivity due to the outflow of lithium ions from the side surface 25A of the inclined hole 25 to the first divided active material layer 5A is as described in the eighth embodiment.

  As described above, in the present embodiment, the portion that penetrates the second divided active material layer 5B extends in the thickness direction of the negative electrode current collector plate 4 and the portion that penetrates the first divided active material layer 5A has the negative electrode current collector 4. A hole 25 inclined with respect to the thickness direction is formed. As a result, the lithium ions quickly pass through the second divided active material layer 5B having a relatively low conductivity and pass through the first divided active material layer 5A having a relatively high ion conductivity at the side surface of the hole 25. It flows out from 25A to the first divided active material layer 5A. As a result, the ion conduction distance until the lithium ions diffuse near the current collector plates 4 and 9 is shortened, and the ion conductivity is increased.

(10th Embodiment)
FIG. 21 is a model diagram for explaining how lithium ions move in the present embodiment. FIG. 21 shows only the negative electrode current collector 4, the first divided active material layer 5A, and the second divided active material layer 5B, but the positive electrode current collector plate 9 and the first divided active material layer 6A. The same applies to the second divided active material layer 6A.

  The hole 25 of each embodiment described above has a uniform cross-sectional shape in the surface direction of the current collector plates 4 and 9 from one end to the other end of the hole 25. However, the hole 25 of this embodiment has at least one of the side surface 25A. The wedge portion is inclined with respect to the thickness direction of the negative electrode current collector plate 4 and becomes narrower as it approaches the negative electrode current collector plate 4.

  The hole 25 of the present embodiment has a side surface 25A that is inclined with respect to the thickness direction of the negative electrode current collector plate 4, thereby being similar to the hole 25 that is inclined with respect to the thickness direction of the negative electrode current collector plate 4. It has a function of improving ion conductivity. Further, when the hole 25 is wedge-shaped as in the present embodiment, the decrease in the volume of the active material layer due to the hole 25 can be reduced as compared with the hole 25 having a uniform cross-sectional shape from one end to the other end. . That is, the capacity loss of the electrode can be reduced.

  In FIG. 21, the inclination of the side surface 25 </ b> A inclined with respect to the thickness direction of the negative electrode current collector plate 4 is constant from one end to the other end of the hole 25, but is not limited thereto. For example, the portion of the side surface 25A that penetrates the second divided active material layer 5B coincides with the thickness direction of the negative electrode current collector plate 4, and the portion that penetrates the first divided active material layer 5A is the thickness of the negative electrode current collector plate 4. The entire side surface 25 </ b> A may be inclined with respect to the thickness direction of the negative electrode current collector plate 4.

  The present invention is not limited to the above-described embodiments, and it goes without saying that various modifications can be made within the scope of the technical idea described in the claims. For example, in the embodiment, the case of a secondary battery has been described, but a primary battery may be used.

# 1 Active material layer forming process # 2 Heating / drying process # 3 Plastic working process # 11 Active material layer forming process # 12 Heating / drying process # 13 Plastic working process # 21 Active material slurry adjusting process # 22 First active material layer Formation process # 23 Second active material layer formation process # 24 Heating / drying process # 25 Plastic working process # 31 Active material slurry adjustment process # 32 First active material layer formation process # 33 Second active material layer formation process # 34 Heating -Drying process # 35 Plastic working process # 41 Transfer seal creating process # 42 First transfer seal attaching process # 43 Second transfer seal attaching process # 44 Plastic working process # 51 Transfer seal creating process # 52 First transfer seal attaching Step # 53 Second transfer seal pasting step # 54 Plastic working step # 61 First transfer seal creating step # 62 Third transfer seal creating step # 63 Pressurizing process # 71 first transfer seal forming step # 72 third transfer seal forming step # 73 pressurizing step 1 the lithium ion secondary batteries 2 power generating element 3 negative (electrode)
4 Negative electrode current collector (current collector)
5 Negative electrode active material layer (active material layer)
5A First divided negative electrode active material layer 5B Second divided negative electrode active material layer 6 Negative electrode active material layer (active material layer)
6A 1st division | segmentation negative electrode active material layer 6B 2nd division | segmentation negative electrode active material layer 8 Positive electrode (electrode)
9 Positive current collector (current collector)
10 Positive electrode active material layer (active material layer)
10A 1st division | segmentation negative electrode active material layer 10B 2nd division | segmentation negative electrode active material layer 11 Positive electrode active material layer (active material layer)
11A First divided negative electrode active material layer 11B Second divided negative electrode active material layer 22 Roller (mold)
23 Convex portion 25 to 28 Hole 31 Spray coater 41, 51 First transfer seal 42, 52 Second transfer seal 41 ', 51' Third transfer seal 43, 44 Transfer sheet

Claims (15)

An electrode having a plurality of holes in the thickness direction formed in the surface direction of the active material layer,
The number of active material particles present per unit volume on the side closer to the current collector of the active material layer is relatively small, and the number of active material particles present per unit volume on the side away from the current collector is relatively An electrode characterized by many. The active material layer is configured by stacking at least two active material layers in the thickness direction,
2. The electrode according to claim 1, wherein among the active material layers, the number of active material particles present per unit volume is smaller in the active material layer closer to the current collector.   2. The electrode according to claim 1, wherein the active material layer continuously decreases in number of active material particles per unit volume as it approaches the current collector from the side opposite to the current collector. .   The electrode according to any one of claims 1 to 3, wherein the hole reaches near the current collector.   The electrode according to any one of claims 1 to 3, wherein the hole penetrates the current collector.   The electrode according to claim 1, wherein at least a part of the hole from one end to the other end is inclined with respect to a thickness direction of the current collector.   The electrode according to claim 6, wherein the hole has a linear portion parallel to a thickness direction of the current collector in at least a part of a portion penetrating the side away from the current collector.   The electrode according to claim 6, wherein the hole has a wedge shape in which at least a part of a side surface is inclined with respect to a thickness direction of the current collector and becomes narrower as the current collector is approached. An active material layer forming step of forming an active material layer on the current collector;
After the active material layer forming step, a plastic working step of drilling a plurality of thickness direction holes in the surface direction of the active material layer,
The number of active material particles present per unit volume on the side closer to the current collector of the active material layer is relatively small, and the number of active material particles present per unit volume on the side away from the current collector is relatively An electrode manufacturing method characterized in that the number of electrodes is large.   In the plastic working step, the number of active material particles present per unit volume of the plastically deformed active material portion is reduced by unidirectional rolling with a mold having convex portions on the surface, and the active material that is not plastically deformed. The method for manufacturing an electrode according to claim 9, which is a step of forming a plurality of holes in the thickness direction in the surface direction of the active material layer while increasing the number of the holes.   The active material layer forming step is a step of preparing a plurality of active material slurries having different numbers of active material particles present per unit volume, and spraying each of the plurality of active material slurries to the current collector in order, After the coating film formed by spraying the previous active material slurry in the order is dried, the coating film is formed by spraying the subsequent active material slurry in the order, and the active material particles present per unit volume The method for producing an electrode according to claim 9, wherein a coating film of the active material slurry having a smaller number of particles is closer to the current collector.   In the active material layer forming step, at least two transfer seals in which active material layers different in the number of active material particles present per unit volume are formed on a transfer sheet are transferred to a unit volume of the active material layer of the transfer seal. The method for producing an electrode according to claim 9, wherein the electrode is a step of being attached so as to be closer to the current collector as the number of active material particles present per unit is smaller. The active material layer forming step includes
A first transfer seal creating step of creating a first transfer seal in which an active material layer having a relatively small number of active material particles per unit volume is formed on a transfer sheet with a predetermined thickness;
A third transfer seal creating step for creating a third transfer seal in which an active material layer having a relatively small number of active material particles per unit volume is formed on the transfer sheet with a thickness greater than the predetermined thickness; ,
The active material layer of the third transfer seal is plastically deformed by pressing the third transfer seal in the thickness direction, and the number of active material particles present per unit volume after the plastic deformation is greater than that of the first transfer seal. A pressurizing step to increase the number,
And a bonding step of forming the active material layer by bonding the third transfer seal and the first transfer seal after plastic deformation in the pressurizing step to the current collector in this order. Item 13. A method for producing an electrode according to Item 12. An electrode manufacturing apparatus that, after forming an active material layer on a current collector, drills a plurality of holes in the thickness direction in the surface direction of the active material layer,
The number of active material particles present per unit volume on the side closer to the current collector of the active material layer is relatively small, and the number of active material particles present per unit volume on the side away from the current collector is relatively Electrode manufacturing apparatus characterized in that the number is increased.   A battery using the electrode according to any one of claims 1 to 8.