Electrode plate manufacturing method and electrode plate manufacturing apparatus

At a first position, an active material layer material is pressurized by first and second rolls, so as to form an active material layer on the second roll. Further, at a third position on a downstream side relative to the first position but on an upstream side relative to, in a rotation direction of the second roll, a second position where a third roll is opposed to the second roll, a part corresponding to a non-formation region in the active material layer is pressurized between a removal surface of the removal portion and the second roll, thereby transferring the pressurized part to the removal surface from the second roll so as to remove the pressurized part. Further, at the second position, the active material layer is transferred onto a surface of a current collector foil from the second roll.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2015-154733 filed on Aug. 5, 2015 including the specification, drawings and abstract is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electrode plate manufacturing method and an electrode plate manufacturing apparatus. More specifically, the present invention relates to an electrode plate manufacturing method and an electrode plate manufacturing apparatus that manufactures an electrode plate such that a belt-shaped current collector foil is conveyed and an active material layer is formed in a part of the conveyed current collector foil in a width direction.

2. Description of Related Art

A battery such as a lithium-ion secondary battery is formed such that positive and negative electrode plates and an electrolyte are accommodated in a case. The positive and negative electrode plates each have a current collector foil and an active material layer. The active material layer contains at least an active material that contributes to charging and discharging, and a binding material that binds the active material onto the current collector foil so as to form the active material layer. A conventional technique related to a manufacturing method of such an electrode plate is disclosed in Japanese Patent Application Publication No. 2014-191880 (JP 2014-191880 A), for example.

JP 2014-191880 A discloses a technique in which a powder constituent containing an active material and so on is supplied to an opposed position of a pair of press rolls from above, and the powder constituent is pressed at the opposed position of the pair of press rolls so as to form an active material layer. Further, in JP 2014-191880 A, a current collector foil is caused to pass the opposed position of the pair of press rolls in a state where the current collector foil is wound around an outer peripheral surface of one of the press rolls. A method described herein is such that an active material layer is formed on a surface of the current collector foil at the opposed position of the pair of press rolls so as to manufacture an electrode plate.

In the meantime, an electrode plate may have a formation region where an active material layer is formed on a current collector foil, and a non-formation region where the current collector foil is exposed. In a device having a configuration of the above conventional technique, in order to manufacture an electrode plate while a formation region and a non-formation region are provided on a current collector foil in a width direction, a powder constituent should be supplied only to a part to become the formation region on the current collector foil. On this account, it is conceivable that a division plate is provided in a boundary between the formation region and the non-formation region so that the powder constituent is supplied only to a formation-region side, for example.

Further, it is preferable that the boundary between the formation region and the non-formation region in the electrode plate be formed in parallel to a conveying direction of the current collector foil. This is to manufacture the electrode plate with a high quality. Further, in order to form the boundary between the formation region and the non-formation region in parallel to the conveying direction of the current collector foil, the division plate should make contact with the current collector foil and the press roll. The reason is as follows: in a case where a gap is formed between the current collector foil or the press roll and the division plate, a powder constituent supplied to a part to become the formation region comes inside a part to become the non-formation region through the gap.

However, in a case where the division plate is provided so as to make contact with the current collector foil or the press roll, the current collector foil or the press roll may be damaged. In a case where the current collector foil or the press roll is damaged, it is difficult to manufacture an electrode plate with a high quality. That is, in the device having the configuration of the conventional technique, it is difficult to manufacture the electrode plate having the formation region and the non-formation region in the width direction while maintaining the high quality.

SUMMARY OF THE INVENTION

The present invention provides an electrode plate manufacturing method and an electrode plate manufacturing apparatus that can manufacture a high-quality electrode plate having a formation region and a non-formation region in a width direction.

An aspect of the present invention relates to a method for manufacturing an electrode plate having a formation region and a non-formation region on a surface of a current collector foil, the formation region being a region in which an active material layer containing at least an active material and a binding material is formed, the non-formation region being a region in which the current collector foil is exposed, the electrode plate being manufactured such that, while the current collector foil having a belt shape is conveyed, the active material layer is formed in a part, in a width direction, of the conveyed current collector foil. The method uses an electrode plate manufacturing apparatus including: a first roll and a second roll placed in parallel to each other and configured to rotate in directions where moving directions of outer peripheral surfaces of the first roll and the second roll at a first position where the outer peripheral surfaces are opposed to each other are both downward along a vertical direction; a third roll placed in parallel to the second roll so as to be opposed to the second roll at a second position different from the first position, the third roll being configured to rotate in a direction where a moving direction of an outer peripheral surface of the third roll at the second position is the same as the moving direction of the outer peripheral surface of the second roll; a removal portion provided at a third position on a downstream side relative to the first position but on an upstream side relative to the second position in a rotation direction of the second roll, the removal portion being configured such that a removal surface opposed to the second roll is moved in the same direction as the moving direction of the outer peripheral surface of the second roll at the third position; and a supply portion configured to supply an active material layer material toward the first position from above the first position, the active material layer material containing at least the active material and the binding material. The second roll is configured to rotate at a circumferential speed faster than a circumferential speed of the first roll. The third roll is configured to rotate at a circumferential speed faster than the circumferential speed of the second roll. The removal portion is configured to move the removal surface at a moving speed faster than a moving speed of the outer peripheral surface of the second roll at the third position. The removal portion includes a projecting portion provided in a region corresponding to the non-formation region so as to project toward the second roll relative to a region corresponding to the formation region. The method includes: pressurizing the active material layer material supplied from the supply portion by the first roll and the second roll both rotating while the active material layer material passes the first position, thereby forming the active material layer such that the active material layer material thus pressurized is attached onto the second roll; pressurizing, in a thickness direction, a part corresponding to the non-formation region in the active material layer by the projecting portion of the removal portion at a time when the active material layer passes the third position between the removal surface and the second roll, thereby transferring the pressurized part of the active material layer to the removal surface from the second roll so as to remove the pressurized part of the active material layer; and conveying the current collector foil by the rotating third roll so as to pass the second position, thereby pressurizing, in the thickness direction, the current collector foil and the active material layer passing the second position between the second roll and the third roll and transferring the active material layer onto the surface of the current collector foil from the second roll.

In the manufacturing method, the part corresponding to the non-formation region in the active material layer formed on the second roll at the first position can be removed by the removal surface of the removal portion from the second roll at the second position. That is, a part around an end portion in the width direction is removed from the active material layer formed by pressurizing the active material layer material. In the part around the end portion in the width direction, the quality easily becomes nonuniform. Hereby, only a part corresponding to the formation region and having a uniform quality in the active material layer thus formed can be left on the second roll. Further, the active material layer corresponding to the formation region on the second roll is transferred onto a surface of the current collector foil from the second roll at the second position. Thus, it is possible to manufacture a high-quality electrode plate having a formation region and a non-formation region in a width direction.

The removal portion may include a removal roll placed in parallel to the second roll such that an outer peripheral surface of the removal roll is opposed to the second roll at the third position, the removal roll being configured to rotate in a direction where a moving direction of the outer peripheral surface of the removal roll at the third position is the same as the moving direction of the outer peripheral surface of the second roll, and a removal film wound around the removal roll and configured to pass the third position by a rotation of the removal roll, the removal film having the removal surface on a surface on a second-roll side. The removal roll may include the projecting portion formed such that the region corresponding to the non-formation region in an axial direction projects radially relative to the region corresponding to the formation region. Since the removal film does not have a high strength, the removal film may meander at the time of passing the third position. Meanwhile, a high-strength material can be used for the removal roll. Accordingly, even at a time when the removal film meanders, it is possible to stably manufacture a high-quality electrode plate.

A second aspect of the present invention relates to an apparatus for manufacturing an electrode plate having a formation region and a non-formation region on a surface of a current collector foil, the formation region being a region in which an active material layer containing at least an active material and a binding material is formed, the non-formation region being a region in which the current collector foil is exposed. The apparatus includes: a first roll and a second roll placed in parallel to each other and configured to rotate in directions where moving directions of outer peripheral surfaces of the first roll and the second roll at a first position where the outer peripheral surfaces are opposed to each other are both downward along a vertical direction; a third roll placed in parallel to the second roll so as to be opposed to the second roll at a second position different from the first position, the third roll being configured to rotate in a direction where a moving direction of an outer peripheral surface of the third roll at the second position is the same as the moving direction of the outer peripheral surface of the second roll; a removal portion provided at a third position on a downstream side relative to the first position but on an upstream side relative to the second position in a rotation direction of the second roll, the removal portion being configured such that a removal surface opposed to the second roll is moved in the same direction as the moving direction of the outer peripheral surface of the second roll at the third position, the removal portion including a projecting portion provided in a region corresponding to the non-formation region so as to project toward the second roll relative to a region corresponding to the formation region; a supply portion configured to supply an active material layer material toward the first position from above the first position, the active material layer material containing at least the active material and the binding material; and a control unit configured to rotate the second roll at a circumferential speed faster than a circumferential speed of the first roll, to rotate the third roll at a circumferential speed faster than the circumferential speed of the second roll, and to cause the removal portion to move the removal surface at a moving speed faster than a moving speed of the outer peripheral surface of the second roll at the third position.

The removal portion may include: a removal roll placed in parallel to the second roll such that an outer peripheral surface of the removal roll is opposed to the second roll at the third position, the removal roll being configured to rotate in a direction where a moving direction of the outer peripheral surface of the removal roll at the third position is the same as the moving direction of the outer peripheral surface of the second roll, and a removal film wound around the removal roll and configured to pass the third position by a rotation of the removal roll, the removal film having the removal surface on a surface on a second-roll side. The projecting portion may be formed such that the region corresponding to the non-formation region in an axial direction projects radially relative to the region corresponding to the formation region.

According to the present invention, it is possible to provide an electrode plate manufacturing method that can manufacture a high-quality electrode plate having a formation region and a non-formation region in a width direction.

DETAILED DESCRIPTION OF EMBODIMENTS

The following describes a best mode for embodying the present invention in detail with reference to the drawings.

First, the following describes an electrode plate100to be manufactured in the present embodiment with reference toFIG. 1. As illustrated in a sectional view ofFIG. 1, the electrode plate100includes a current collector foil110and an active material layer120. The electrode plate100is elongated in a depth direction inFIG. 1.

In the electrode plate100of the present embodiment, the active material layer120is formed only on a first surface111of the current collector foil110. The electrode plate100is used as a positive electrode or a negative electrode for constituting a secondary battery such as a lithium-ion secondary battery, for example. When the electrode plate100is used as a positive electrode or a negative electrode in manufacture of a secondary battery, the electrode plate100is cut in a necessary size as appropriate.

As the current collector foil110, a metal foil can be used, for example. Further, the active material layer120contains at least an active material131and a binding material132. The active material131contributes to charging and discharging in a battery. Further, the binding material132binds materials constituting the active material layer120to each other so as to form the active material layer120and also binds the active material layer120to the first surface111of the current collector foil110.

More specifically, in a case where the electrode plate100is a positive electrode of a lithium-ion secondary battery, an aluminum foil can be used as the current collector foil110, LiNi0.5Mn1.5O4can be used as the active material131, and polyvinylidene fluoride (PVDF) can be used as the binding material132, for example. In a case where the electrode plate100is a negative electrode of a lithium-ion secondary battery, a copper foil can be use as the current collector foil110, a carbon material can be used as the active material131, and carboxymethyl cellulose (CMC) can be used as the binding material132, for example. Note that the active material layer120may further contain a material except for the active material131and the binding material132, e.g., a conductive material for raising conductivity in the active material layer120, or the like as appropriate.

Further, as illustrated inFIG. 1, the electrode plate100of the present embodiment has: a formation region M where the active material layer120is formed on the first surface111of the current collector foil110; and non-formation regions N1, N2where the active material layer120is not formed and the first surface111of the current collector foil110is exposed. The non-formation regions N1, N2are provided at both ends of the electrode plate100in the width direction, which is a right-left direction inFIG. 1. The formation region M is provided in a center in the width direction, sandwiched between the non-formation regions N1, N2at both ends. That is, the formation region M and the non-formation regions N1, N2extend in a longitudinal direction of the electrode plate100. Note that a length of the formation region M in the width direction is indicated by a length LM inFIG. 1.

Next will be described an electrode plate manufacturing apparatus to be used in manufacture of the electrode plate100of the present embodiment.FIG. 2is a schematic configuration diagram of an electrode plate manufacturing apparatus1of the present embodiment. InFIG. 2, an X-axis along the right-left direction and a Y-axis along an up-down direction are shown. Note that a depth direction inFIG. 2is assumed a Z-axis. As illustrated inFIG. 2, the electrode plate manufacturing apparatus1includes a first roll10, a second roll20, a third roll30, a removal portion40, and a powder supply portion70. InFIG. 2, the up-down direction is a vertical direction, and the gravity works downward.

As illustrated inFIG. 2, the first roll10, the second roll20, and the third roll30are all placed in a state where an axial direction thereof is along a horizontal direction. The first roll10, the second roll20, and the third roll30are made of a material having a high strength such as metal, for example. Further, the first roll10and the second roll20are placed in parallel to each other in a state where their outer peripheral surfaces11,21are opposed to each other at a first opposed position A. Further, the third roll30is placed in parallel to the second roll20in a state where their outer peripheral surfaces21,31are opposed to each other at a second opposed position B.

Further, the first roll10and the second roll20are held so that a shaft distance therebetween is a given interval. A gap GA is provided between the outer peripheral surface11of the first roll10and the outer peripheral surface21of the second roll20at the first opposed position A. Further, the third roll30is held so that a shaft distance between the third roll30and the second roll20is a given interval. A gap GB is provided between the outer peripheral surface21of the second roll20and the outer peripheral surface31of the third roll30at the second opposed position B.

Further, the first roll10, the second roll20, the third roll30are configured to rotate when the electrode plate100is manufactured. InFIG. 2, respective rotation directions of the first roll10, the second roll20, and the third roll30are indicated by respective arrows. As illustrated inFIG. 2, the rotation directions of the first roll10and the third roll30are clockwise, and the rotation direction of the second roll20is counterclockwise.

That is, the rotation directions of the first roll10and the second roll20are directions in which moving directions of the outer peripheral surfaces11,21at the first opposed position A are both downward along the vertical direction. Further, the second roll20rotates at a circumferential speed faster than a circumferential speed of the first roll10. Further, the rotation direction of the third roll30is a direction in which a moving direction of the outer peripheral surface31at the second opposed position B is the same as a moving direction of the outer peripheral surface21of the second roll20. Further, the third roll30rotates at a circumferential speed faster than the circumferential speed of the second roll20.

The powder supply portion70is provided above the first opposed position A where the first roll10and the second roll20are opposed to each other. The powder supply portion70can supply a powder constituent130accommodated thereinside by dropping the powder constituent130. That is, the powder supply portion70can supply the powder constituent130toward the first opposed position A from above the first opposed position A. As illustrated inFIG. 2, the powder constituent130supplied from the powder supply portion70is accumulated between the first roll10and the second roll20on an upper side at the first opposed position A.

The powder constituent130is an active material layer material containing powdery materials for forming the active material layer120. The powder constituent130of the present embodiment contains the active material131and the binding material132. Further, particles in the powder constituent130of the present embodiment are granulated particles obtained by granulating the active material131and the binding material132. Note that, in a case where the active material layer120is formed so as to contain a material such as a conductive material as well as the active material131and the binding material132, powder of the material is mixed into the powder constituent130.

Further, a division plate71is provided between the first roll10and the second roll20above the first opposed position A.FIG. 3is a plan view at the first opposed position A. InFIG. 3, the X-axis direction is the right-left direction and the Z-axis direction is the up-down direction. As illustrated inFIG. 3, a pair of division plates71is provided. The division plates71are provided an interval having a length LK therebetween.

The powder constituent130is supplied to between the pair of division plates71by the powder supply portion70, so as to be accumulated between the pair of division plates71as illustrated inFIG. 3. The division plates71can restrict positions of the powder constituent130in the axial direction of the first roll10and the second roll20. The powder constituent130is accumulated between the first roll10and the second roll20above the first opposed position A. Note that, in the present embodiment, the length LK of the interval between the pair of division plates71is at least a length LM, in the width direction, of the formation region M in the electrode plate100.

Further, in the present embodiment, as illustrated inFIG. 2, the division plates71are placed with a gap GK with respect to the outer peripheral surface11of the first roll10and the outer peripheral surface21of the second roll20. That is, the division plates71do not make contact with the first roll10and the second roll20. Accordingly, in the electrode plate manufacturing apparatus1, the division plates71do not make contact with the first roll10and the second roll20, thereby restraining the outer peripheral surfaces11,21from being damaged.

The removal portion40is provided at a removal position C placed on a downstream side relative to the first opposed position A but on an upstream side relative to the second opposed position B in the rotation direction of the second roll20. Further, the removal portion40of the present embodiment is constituted by a removal roll50and a removal film60. The removal roll50is also placed in a state where its axial direction is along the horizontal direction. The removal roll50is made of a material having a high strength such as metal, for example.

FIG. 4is a sectional view at the removal position C. InFIG. 4, the Z-axis direction is the right-left direction and the Y-axis direction is the up-down direction. As illustrated inFIG. 4, the removal roll50includes large-diameter portions51placed at both axial ends, and a small-diameter portion55placed in a center in the axial direction so as to be sandwiched between the large-diameter portions51at both ends. The large-diameter portions51have a diameter larger than that of the small-diameter portion55, and project in a radial direction. In view of this, the large-diameter portions51are parts projecting toward the second roll20relative to the small-diameter portion55. That is, the large-diameter portion51can be regarded as a “projecting portion”. InFIG. 4, a difference D between a radius of the large-diameter portion51and a radius of the small-diameter portion55is shown.

Further, an interval with a length LM is provided between the large-diameter portions51at both ends of the removal roll50. Accordingly, the large-diameter portions51are provided in regions corresponding to the non-formation regions N1, N2of the electrode plate100. Further, the small-diameter portion55is provided in a region corresponding to the formation region M of the electrode plate100.

Further, the removal roll50is placed in parallel to the second roll20in a state where outer peripheral surfaces52of the large-diameter portions51are opposed to the outer peripheral surface21of the second roll20at the removal position C. At the time of manufacturing the electrode plate100, the removal roll50rotates clockwise as indicated by an arrow inFIG. 2. That is, a rotation direction of the removal roll50is a direction in which a moving direction of the outer peripheral surfaces52at the removal position C is the same as the moving direction of the outer peripheral surface21of the second roll20.

The removal film60is an elongated belt-shaped member. As the removal film60, a film having a thickness of 5 μm to 100 μm can be used. In the present embodiment, as the removal film60, a film made of polyethylene terephthalate (PET) and having a thickness of 50 μm is used. Note that, as the removal film60, a resin film other than PET, e.g., films made of polypropylene (PP), polystyrene (PS), polyvinylchloride (PVC), polyimide (PI), and the like can be used.

As illustrated inFIG. 2, the removal film60is wound around the removal roll50at the removal position C. Because of this, at the time of the manufacture of the electrode plate100, the removal film60is conveyed by the rotating removal roll50. That is, as illustrated inFIG. 2, the removal film60is conveyed to move from a bottom left of the removal roll50toward the removal position C, and then move toward a bottom right of the removal roll50after the removal film60passes the removal position C.

Further, when the removal film60is conveyed, the removal film60passes the removal position C in a state where a first surface61faces a second-roll-20side and a second surface62faces a removal-roll-50side. On this account, the first surface61of the removal film60is a surface opposed to the second roll20. Further, the removal roll50is held so that a shaft distance between the removal roll50and the second roll20is a given interval. A gap GC is provided between the first surface61of the removal film60and the outer peripheral surface21of the second roll20at the removal position C.

As described above, the second roll20and the removal roll50rotate in directions where moving directions of the outer peripheral surfaces21,52at the removal position C are the same. On this account, the first surface61of the removal film60at the removal position C moves in the same direction as the moving direction of the outer peripheral surface21of the second roll20at the removal position C. Further, the removal roll50of the present embodiment rotates such that a circumferential speed of the large-diameter portions51is faster than the circumferential speed of the second roll20. On this account, a moving speed of the first surface61of the removal film60at the removal position C is faster than the circumferential speed of the second roll20.

As illustrated inFIG. 4, the first surface61and the second surface62of the removal film60are both flat. As illustrated inFIG. 4, the second surface62of the removal film60is wound around the outer peripheral surface52of the large-diameter portion51of the removal roll50. That is, the second surface62of the removal film60does not make contact with an outer peripheral surface56of the small-diameter portion55. This is because there is a difference D in radius between the large-diameter portions51and the small-diameter portion55.

Further, a current collector foil110is wound around the outer peripheral surface31of the third roll30as illustrated inFIG. 2. The current collector foil110is wound around the third roll30in a state where a width direction of the current collector foil110is set along the axial direction of the third roll30. Further, in a state where a second-surface-112side faces the outer peripheral surface31of the third roll30, the current collector foil110is wound at the second opposed position B of the third roll30. Hereby, the current collector foil110is conveyed by a rotation of the third roll30.

Further, a first surface111of the current collector foil110is opposed to the outer peripheral surface21of the second roll20at the second opposed position B. Note that, as described above, the third roll30rotates at the circumferential speed faster than that of the second roll20. Therefore, a moving speed of the first surface111of the current collector foil110at the second opposed position B is faster than a moving speed of the outer peripheral surface21of the second roll20at the second opposed position B.

Further, as illustrated inFIG. 2, the current collector foil110is supplied into the electrode plate manufacturing apparatus1from a bottom right of the third roll30, and after the current collector foil110passes the second opposed position B, the current collector foil110is conveyed so as to be discharged toward an upper right of the third roll30. When the current collector foil110is supplied to the electrode plate manufacturing apparatus1, nothing is formed on the first surface111. The electrode plate manufacturing apparatus1can manufacture the electrode plate100such that the active material layer120is formed on the first surface111of the current collector foil110at the second opposed position B. Note that the rotation speeds of the first roll10, the second roll20, the third roll30, and the removal roll50, a conveyance speed of the removal film60, and a supply speed of the powder constituent130from the powder supply portion70to the first opposed position A are controlled by an ECU300.

Next will be described a manufacturing method of the electrode plate100of the present embodiment by use of the electrode plate manufacturing apparatus1. At the time of the manufacture of the electrode plate100, the powder constituent130is supplied to between the pair of division plates71by the powder supply portion70. The powder constituent130thus supplied and accumulated between the pair of division plates71is sent to the first opposed position A sequentially from particles on a lower side by rotations of the first roll10and the second roll20.

The powder constituent130that has reached the first opposed position A passes the gap GA by the rotations of the first roll10and the second roll20. At the time when the powder constituent130passes the gap GA, the powder constituent130is pressurized between the outer peripheral surface11of the first roll10and the outer peripheral surface21of the second roll20. Due to the pressurization, the particles in the powder constituent130are bound together due to an operation of the binding material132in the powder constituent130. Hereby, the powder constituent130that has passed the first opposed position A is shaped into the sheet-shaped active material layer121.

The active material layer121formed at the first opposed position A is attached to a surface that moves at a faster moving speed at the first opposed position A, out of the outer peripheral surface11of the first roll10and the outer peripheral surface21of the second roll20. As described above, the circumferential speed of the second roll20is faster than that of the first roll10. That is, the active material layer121formed at the first opposed position A is attached to the second roll20. Accordingly, as illustrated inFIG. 2, the active material layer121formed at the first opposed position A is attached onto the outer peripheral surface21of the second roll20that has passed the first opposed position A.

Further, the active material layer121formed at the first opposed position A is then conveyed by the rotation of the second roll20, as illustrated inFIG. 2, and passes the removal position C and the second opposed position B in this order. Hereby, the electrode plate100is manufactured at the second opposed position B.FIG. 5is a plan view of an active material layer after the active material layer is formed at the first opposed position A until the electrode plate100is manufactured. InFIG. 5, the first opposed position A, the removal position C, and the second opposed position B are shown. That is, a direction where the active material layer is conveyed is a right side. Further, the up-down direction inFIG. 5is a width direction of the active material layer.

A length, in the width direction, of the active material layer121which is formed at the first opposed position A but which has not reached the removal position C is longer than the length LK of the interval between the pair of division plates71, as illustrated inFIG. 5. Further, the length, in the width direction, of the active material layer121formed at the first opposed position A is not uniform. That is, both ends, in the width direction, of the active material layer121formed at the first opposed position A are not parallel to the conveying direction but distorted in a waveform.

Further,FIG. 6is a sectional view of the active material layer121formed at the first opposed position A. As illustrated inFIG. 6, in the active material layer121, its thickness is uniform in a central part122corresponding to a part (indicated by the length LK) between the pair of division plates71. In the meantime, thicknesses at end portions123, which are both ends outside the central part122in the width direction, are thinner than the central part122. Further, as the end portion123is farther from the central part122and closer to an end, the end portion123becomes thinner. That is, in the active material layer121which is formed at the first opposed position A but which has not reached the removal position C, the quality of parts near both ends in the width direction is not uniform both in terms of the width direction and the conveying direction.

As described above, the gap GK is provided between the division plate71and each of the outer peripheral surface11of the first roll10and the outer peripheral surface21of the second roll20. Further, the gap GA between the first roll10and the second roll20is small at the first opposed position A. Because of this, as illustrated inFIG. 2, the division plate71is not inserted up to the first opposed position A, so the division plate71cannot restrict the powder constituent130at the first opposed position A. The end portions123of the active material layer121formed at the first opposed position A are parts formed of the powder constituent130that passes the gap GK and the like and protrudes outside the pair of division plates71before the powder constituent130passes the first opposed position A. That is, the active material layer121formed by pressurizing the powder constituent130easily becomes nonuniform in quality around the end portions in the width direction.

Subsequently, the active material layer121on the outer peripheral surface21of the second roll20is conveyed by the rotation of the second roll20as illustrated inFIG. 2, and reaches the removal position C at which the removal portion40is provided. The active material layer121that has reached the removal position C passes the gap GC, and at a time when the active material layer121passes the gap GC, the active material layer121is pressurized in its thickness direction between the outer peripheral surface21of the second roll20and the first surface61of the removal film60.

Here, as described above, the second surface62of the removal film60makes contact with the outer peripheral surfaces52of the large-diameter portions51of the removal roll50, but does not make contact with the outer peripheral surface56of the small-diameter portion55. On this account, as illustrated inFIG. 4, only end portions124of the active material layer121are pressurized. The end portions124are placed at both ends of the active material layer121in the width direction and opposed to the large-diameter portions51of the removal roll50. As described above, the moving speed of the first surface61of the removal film60at the removal position C is faster than the circumferential speed of the second roll20.

At the removal position C, the pressurized end portions124of the active material layer121are attached to a surface that moves at a faster moving speed at the removal position C, out of the outer peripheral surface21of the second roll20and the first surface61of the removal film60. Accordingly, at the removal position C, the end portions124of the active material layer121are transferred onto the first surface61of the removal film60from the outer peripheral surface21of the second roll20. Thus, as illustrated inFIG. 2, only the end portions124of the active material layer121are attached onto the first surface61of the removal film60that has passed the removal position C. Hereby, the end portions124of the active material layer121are removed from the outer peripheral surface21of the second roll20. Further, the end portions124of the active material layer121thus removed at the removal position C are regions corresponding to the non-formation regions N1, N2of the electrode plate100. This is because the large-diameter portions51are provided in regions corresponding to the non-formation regions N1, N2of the electrode plate100, as described above.

Meanwhile, an active material layer120is left on the outer peripheral surface of the second roll20that has passed the removal position C so that the end portions124have been removed therefrom, as illustrated inFIG. 2. The active material layer120is a central part of the active material layer121, and the central part has not been pressurized at the removal position C, as illustrated inFIG. 4. Further, the active material layer120is a part opposed to the small-diameter portion55of the removal roll50at the removal position C, and a length thereof in the width direction is the length LM of the interval between the large-diameter portions51at both ends of the removal roll50. That is, the active material layer120is attached to a region of the outer peripheral surface21of the second roll20, the region corresponding to the formation region M of the electrode plate100.

As illustrated in a plan view ofFIG. 5, a length, in the width direction, of the active material layer120that has passed the removal position C is maintained uniform at the length LM. Because of this, the active material layer120that has passed the removal position C is formed such that both ends thereof in the width direction are parallel to the conveying direction. Further,FIG. 7is a sectional view of the active material layer120that has passed the removal position C. As illustrated inFIG. 7, a thickness of the active material layer120in the width direction is uniform. That is, the active material layer120that has passed the removal position C has a uniform quality both in terms of the width direction and the conveying direction.

As described above, the length, in the width direction, of the active material layer121that has not reached the removal position C is longer than the length LK of the interval between the pair of division plates71. Further, the length LK of the interval between the pair of division plates71is at least the length LM, in the width direction, of the formation region M in the electrode plate100. That is, the active material layer120that has passed the removal position C is obtained such that the end portions124including the end portions123that are nonuniform in quality are removed from the active material layer121that is nonuniform in quality around both ends. Further, the active material layer120that has passed the removal position C is the central part122of the active material layer121. The quality of the central part122is uniform because its thickness is uniform.

Subsequently, the active material layer120on the outer peripheral surface21of the second roll20that has passed the removal position C is conveyed by the rotation of the second roll20as illustrated inFIG. 2, and reaches the second opposed position B. The current collector foil110is conveyed to pass the second opposed position B as illustrated inFIG. 2. On this account, the active material layer120that has reached the second opposed position B by the rotation of the second roll20passes the gap GB together with the current collector foil110. At the time of passing the gap GB, the current collector foil110and the active material layer120are pressurized by the second roll20and the third roll30in their thickness direction. Further, as described above, the third roll30of the present embodiment rotates at a circumferential speed at which a moving speed of the first surface111of the current collector foil110at the second opposed position B is faster than the circumferential speed of the second roll20.

Also at the second opposed position B, the active material layer120thus pressurized is attached to a surface that moves at a faster moving speed at the second opposed position B, out of the outer peripheral surface21of the second roll20and the first surface111of the current collector foil110. Hereby, at the second opposed position B, the active material layer120is transferred onto the first surface111of the current collector foil110from the outer peripheral surface21of the second roll20. Therefore, as illustrated inFIG. 2, the active material layer120is transferred to the first surface111of the current collector foil110that has passed the second opposed position B. Thus, the electrode plate100is manufactured.

Further, as illustrated inFIG. 5, the formation region M and the non-formation regions N1, N2are provided in the electrode plate100that has passed the second opposed position B. The active material layer120formed in the formation region M has a uniform quality both in terms of the width direction and the conveying direction. Accordingly, in the present embodiment, the high-quality electrode plate100having the formation region M and the non-formation regions N1, N2in the width direction is manufactured by using the electrode plate manufacturing apparatus1.

Note that, in the electrode plate manufacturing apparatus1of the present embodiment, a circumferential speed ratio A, represented by a ratio of the circumferential speed of the second roll20with respect to the circumferential speed of the first roll10, is preferably 4/3 or more. When the circumferential speed ratio A is 4/3 or more, the active material layer121formed by the powder constituent130passing the first opposed position A can be successfully attached to the outer peripheral surface21of the second roll20.

Further, the inventor performed an experiment in which electrode plates100were manufactured by use of the electrode plate manufacturing apparatus1using different circumferential speed ratios between opposed rolls at the first opposed position A, the second opposed position B, and the removal position C. In this experiment, a copper foil of 8 μm was used as the current collector foil110. Further, as the powder constituent130to be supplied from the powder supply portion70, granulated particles obtained by granulating graphite as the active material131and carboxymethyl cellulose (CMC) as the binding material132were used. Then, the first roll10, the second roll20, the third roll30, and the removal roll50were rotated at respective circumferential speeds shown in Table 1, so as to manufacture the electrode plates100.

In Table 1, the circumferential speed ratio A, which is a ratio of the circumferential speed of the second roll20with respect to the circumferential speed of the first roll10, is shown. Further, a circumferential speed ratio B shown in Table 1 is a ratio of the circumferential speed of the third roll30with respect to the circumferential speed of the second roll20. A circumferential speed ratio C is a ratio of the circumferential speed of the removal roll50with respect to the circumferential speed of the second roll20. As shown in Table 1, the circumferential speed ratio B and the circumferential speed ratio C take smaller values from Example 1 to Example 6.

In the experiment, an electrode plate100having a formation region M and non-formation regions N1, N2was able to be manufactured in each example. This is because, as shown in Table 1, the second roll20rotates at a circumferential speed faster than the circumferential speed of the first roll10in each example. This is also because both the third roll30and the removal roll50rotate at a circumferential speed faster than the circumferential speed of the second roll20in each example.

Note that, in each example, the circumferential speed ratio A is 5/3, which is 4/3 or more. As a result, in each example, an active material layer121was able to be formed successfully on the second roll20at the first opposed position A.

Further, Table 1 shows evaluations of the electrode plates100manufactured in respective examples. As shown in Table 1, Example 1 and Example 6 are evaluated as a “Δ.” This is because, in each of the electrode plates100of Example 1 and Example 6, a first surface111of a current collector foil110in non-formation regions N1, N2was not completely exposed. That is, in each of Example 1 and Example 6, end portions124of an active material layer121were not completely removed by the removal portion40, and the end portions124of the active material layer121, slightly left on the second roll20, were transferred to the first surface111of the current collector foil110.

Meanwhile, Examples 2 to 5 are evaluated as a “∘.” That is, in each of Examples 2 to 5, end portions124of an active material layer121were able to be successfully removed by the removal portion40. Each of the electrode plates100manufactured in Examples 2 to 5 had non-formation region N1, N2where a first surface111of a current collector foil110was exposed successfully. Thus, according to the experiment, it is found that the circumferential speed ratio B and the circumferential speed ratio C are preferably within a range of not less than 4/3 but not more than 2.

Further, in the above description, the removal portion40is constituted by the removal roll50having the large-diameter portions51and the small-diameter portion55with a radius difference D therebetween, and the removal film60in which the first surface61and the second surface62are both flat. However, other configurations can be used. For example, in the electrode plate manufacturing apparatus1, a removal portion140as one modification illustrated inFIG. 8can be used instead of the afore-mentioned removal portion40.

FIG. 8is a sectional view of the removal portion140at a removal position C. InFIG. 8, the Z-axis direction is the right-left direction and the Y-axis direction is the up-down direction. The removal portion140is constituted by a removal roll150and a removal film160. The removal roll150is placed in parallel to the second roll20such that an outer peripheral surface151is opposed to the outer peripheral surface21of the second roll20at the removal position C. Note that the removal roll150of the removal portion140is configured such that its diameter along the axial direction is uniform, which is different from the removal roll50of the removal portion40.

Further, the removal film160of the removal portion140is an elongated belt-shaped member, and is wound around the removal roll150at the removal position C. On this account, when the removal film160is also conveyed by a rotation of the removal roll150, the removal film160passes the removal position C in a state where a first surface161faces the second-roll-20side and a second surface162faces the removal-roll-150side.

Note that a recessed portion165is formed in a center, in the width direction, of the removal film160of the removal portion140, which is different from the removal film60of the removal portion40. That is, the removal film160illustrated inFIG. 8includes end portions163placed at both axial ends in the width direction, and a central portion164placed in a center, in the width direction, sandwiched between the end portions163at both ends and having a thickness thinner than the end portions163. Accordingly, the end portions163are parts projecting toward the second roll20relative to the central portion164. That is, in the removal portion140ofFIG. 8, the end portion163can be regarded as a “projecting portion”.FIG. 8shows a difference D in thickness between the end portion163and the central portion164in the removal film160.

Further, an interval with a length LM is provided between the end portions163placed at both ends of the removal film160. Hereby, the end portions163of the removal film160are provided in regions corresponding to the non-formation regions N1, N2of the electrode plate100. Further, the central portion164of the removal film160is provided in a region corresponding to the formation region M of the electrode plate100.

Consequently, with the use of the removal portion140illustrated inFIG. 8, only the end portions124of the active material layer121on the outer peripheral surface21of the second roll20are pressurized at the removal position C. The end portions124are placed at both ends, in the width direction, of the active material layer121so as to be opposed to the end portions163of the removal film160. Accordingly, at the removal position C, the end portions124of the active material layer121can be transferred to the first surface161of the removal film160from the outer peripheral surface21of the second roll20so as to remove the end portions124from the outer peripheral surface21of the second roll20. Accordingly, even in a case where the removal portion140illustrated inFIG. 8is used, it is possible to manufacture the electrode plate100having the formation region M and the non-formation regions N1, N2provided appropriately.

Note that, in a case where the removal portion140illustrated inFIG. 8is used, the removal film160to be conveyed may meander in the width direction at the removal position C. This is because the strength of the removal film160is not so high. In a case where the removal film160meanders, a boundary between the formation region M and each of the non-formation regions N1, N2may not be formed in parallel to the conveying direction of the current collector foil110. This is because, along with meandering of the removal film160, a position of the active material layer121to be pressurized on the second roll20is displaced in the width direction.

In the meantime, in a case of the afore-mentioned removal portion40, even if the removal film60meanders, the large-diameter portions51of the removal roll50can always pressurize regions corresponding to the non-formation regions N1, N2appropriately. This is because the removal roll50has a strength higher than that of the removal film60. This accordingly allows the removal portion40to stably manufacture the electrode plate100with a high quality, as compare with the removal portion140of the modification.

Also, a removal portion240illustrated inFIG. 9may be used instead of the removal portion40in the electrode plate manufacturing apparatus1.FIG. 9is a sectional view of the removal portion240in a modification different fromFIG. 8, at the removal position C. InFIG. 9, the Z-axis direction is the right-left direction and the Y-axis direction is the up-down direction. The removal portion240includes a removal roll250as illustrated inFIG. 9. However, the removal portion240does not include the removal film60of the removal portion40.

The removal roll250includes large-diameter portions251placed at both axial ends, and a small-diameter portion255placed in a center in the axial direction so as to be sandwiched between the large-diameter portions251at both ends. In view of this, the large-diameter portions251are parts projecting toward the second roll20relative to the small-diameter portion255. That is, in the removal portion240ofFIG. 9, the large-diameter portion251can be regarded as a “projecting portion”. InFIG. 9, a difference D between a radius of the large-diameter portion251and a radius of the small-diameter portion255is shown. Further, an interval with a length LM is also provided between the large-diameter portions251at both ends of the removal roll250. Hereby, the large-diameter portions251are provided in regions corresponding to the non-formation regions N1, N2of the electrode plate100. Further, the small-diameter portion255is provided in a region corresponding to the formation region M of the electrode plate100.

Further, the removal roll250is also configured such that outer peripheral surfaces252of the large-diameter portions251are opposed to the outer peripheral surface21of the second roll20at the removal position C. Further, the removal roll250is also placed in parallel to the second roll20.

Accordingly, in a case of the removal portion240illustrated inFIG. 9, only the end portions124of the active material layer121on the outer peripheral surface21of the second roll20are pressurized at the removal position C. The end portions124are placed at both ends, in the width direction, of the active material layer121so as to be opposed to the large-diameter portions251of the removal roll250. This is because an outer peripheral surface256of the small-diameter portion255of the removal roll250does not make contact with the active material layer121. Further, inFIG. 9, the end portions124of the active material layer121can be transferred onto the outer peripheral surfaces252of the large-diameter portions251of the removal roll250from the outer peripheral surface21of the second roll20at the removal position C, so as to remove the end portions124from the outer peripheral surface21of the second roll20. Accordingly, even in a case where the removal portion240illustrated inFIG. 9is used, it is possible to manufacture the electrode plate100having the formation region M and the non-formation regions N1, N2provided appropriately.

The end portions124of the active material layer121, transferred onto the outer peripheral surfaces252of the large-diameter portions251of the removal roll250at the removal position C, are removed from the removal roll250before they reach the removal position C again by a rotation of the removal roll250. On this account, as illustrated in a front view ofFIG. 10, a blade270may be provided to make contact with the outer peripheral surfaces252of the large-diameter portions251of the removal roll250. The blade270removes the transferred end portions124of the active material layer121by scraping. Further, when the end portions124of the active material layer121are removed by the blade270from the removal roll250, the end portions124are recovered and subjected to processes such as crushing, so as to be used as the powder constituent130again.

Further, in the electrode plate manufacturing apparatus1of the present embodiment, the difference D in radius between the large-diameter portion51and the small-diameter portion55of the removal roll50is preferably 10 μm or more. The reason is as follows. That is, when the difference D is too small, the active material layer120attached to a region corresponding to the formation region M on the second roll20may be pressurized at the removal position C. As a result, a pressurized part of the active material layer120might be transferred onto the first surface61of the removal film60. That is, when the difference D in radius between the large-diameter portion51and the small-diameter portion55of the removal roll50is 10 μm or more, the active material layer120attached to the region corresponding to the formation region M on the second roll20can be left on the second roll20appropriately even after the active material layer120has passed the removal position C. The same can apply to the difference D in the modifications inFIGS. 8 and 9.

As specifically described above, in the electrode plate manufacturing apparatus1of the present embodiment, the end portions124, corresponding to the non-formation regions N1, N2, in the active material layer121formed on the outer peripheral surface of the second roll20are removed from the second roll20by the removal portion40at the removal position C. That is, it is possible to remove the end portions of the active material layer121and its vicinal area where the quality easily becomes nonuniform. Accordingly, the active material layer120transferred to the first surface111of the current collector foil110at the second opposed position B has a uniform quality both in terms of the width direction and the conveying direction. Consequently, the electrode plate100manufactured by transferring the active material layer120to the current collector foil110at the second opposed position B has a high quality. Hereby, it is possible to achieve an electrode plate manufacturing method that can manufacture a high-quality electrode plate having a formation region and a non-formation region in a width direction.

Note that the present embodiment is merely an example, and is not intended to limit the present invention at all. Accordingly, it goes without saying that the present invention can be altered or modified variously within a range which does not deviate from the gist of the present invention. For example, the above embodiment deals with a case where the active material layer120is formed only on the first surface111of the current collector foil110, but the active material layer120can be formed on the second surface112of the current collector foil110. For example, the active material layer120can be formed on the second surface112of the current collector foil110in the same manner as a case where the active material layer is formed on the first surface111as described above.

Further, the division plates71may not be provided. However, in a case where the division plates71are not provided, the powder constituent130accumulated between the first roll10and the second roll20above the first opposed position A easily protrudes outward relative to the region corresponding to the formation region M. Because of this, in a case where the division plates71are not provided, an amount of the end portions124of the active material layer121to be removed by the removal portion40from the second roll20at the removal position C increases. In view of this, by providing the division plates71, it is possible to increase a yield.

Further, for example, the above embodiment deals with the electrode plate100in which the formation region M is provided in the center in the width direction and the non-formation regions N1, N2are provided at both ends. However, the arrangement of the formation region and the non-formation regions is not limited to that of the electrode plate100. For example, the present invention can be applied to manufacture of an electrode plate in which a non-formation region is provided in a center in a width direction and formation regions are provided at both ends. Alternatively, the present invention can be also applied to manufacture of an electrode plate in which a formation region is provided in one end in a width direction and a non-formation region is provided in the other end.

Further, for example, the above embodiment deals with a case where the powder constituent130made of granulated particles of the active material131and the binding material132is used as an active material layer material to be supplied to the first opposed position A. However, the granulated particles may not necessarily be used as the active material layer material. That is, as the active material layer material, it is possible to use a powder constituent obtained by mixing powders of materials necessary to form the active material layer120. Alternatively, the active material layer material is not limited to a powdered material, but a material containing a solvent together with the active material131, the binding material132, and so on is also usable.