JP2011222206A - Device and method for manufacturing electrode, electrode, and lithium ion battery using electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode manufacturing device capable of controlling a position of a metallic foreign particle in an electrode.SOLUTION: This device includes current collector transportation means (11, 12, 13) for moving a plate-like current collector (14), electrode formation means (8) for forming the electrode by applying active material slurry on one face of the current collector (14) and forming an active material layer, and magnetic field generation means (21) for applying a magnetic field to the active material slurry (15) applied to the current collector (14) from the other face of the current collector (14), on which the active material slurry is applied.

Description

  The present invention relates to an electrode manufacturing apparatus, a manufacturing method, an electrode, and a lithium ion battery using the electrode.

  If the active material contains foreign material such as metal (hereinafter referred to as “metal foreign material”) as a contamination (contaminant), or if metal foreign particles generated in the process of creating the electrode are mixed into the active material Battery performance deteriorates due to self-discharge. For this reason, before forming an active material slurry with an active material and a solvent, an active material transport pipe is formed of a magnetic material to remove foreign metal particles contained in the active material (Patent Document 1). reference).

JP 2001-243947 A

  However, if the metal foreign particles are small, the amount of magnetization of the metal foreign particles is also small, so that the metal foreign particles are not stably adsorbed on the transport pipe and the metal foreign particles may still remain in the active material. Therefore, when the battery is manufactured, the foreign metal particles may be deposited and grown locally on the separator surface, causing an internal short circuit.

  Therefore, an object of the present invention is to provide an electrode manufacturing apparatus and an electrode manufacturing method capable of controlling the position of the metal foreign particles in the electrode, without intentionally removing the metal foreign particles.

  The present invention includes a current collector conveying means for moving a current collector, an electrode forming means for forming an electrode by applying an active material slurry to one surface of the current collector to form an active material layer, Magnetic field generating means for applying a magnetic field to the active material slurry applied to the current collector from the other surface side of the current collector applied with the active material slurry.

  According to the present invention, the foreign metal particles in the active material slurry applied to one surface of the current collector are attracted to the current collector side by a magnetic field. Can be arranged. Therefore, when the battery is manufactured, the metal foreign particles are located at a position far from the separator, so that the metal foreign particles change to metal ions due to charge / discharge after the battery is manufactured, and these metal ions are collected on the separator side (collected). In the process of moving to the opposite side of the electric body, the metal foreign particles are diffused more than when they are present at a position close to the separator. The internal short circuit can be suppressed by the difference in the degree of diffusion.

It is a schematic block diagram of the electrode manufacturing apparatus of 1st Embodiment of this invention. It is a partial schematic perspective view of the same electrode manufacturing apparatus. It is an expansion perspective view of a backup roll part. It is sectional drawing of the cell using the electrode manufactured with the conventional electrode manufacturing apparatus. It is sectional drawing of the cell using the electrode manufactured with the electrode manufacturing apparatus of this invention. It is a state diagram for demonstrating the influence which a magnetic force has on the state in a coating film. It is a state figure which shows the state in the coating film before passing after passing a permanent magnet. It is a schematic block diagram of the electrode manufacturing apparatus of 2nd Embodiment.

  1 is a schematic configuration diagram of an electrode manufacturing apparatus according to an embodiment of the present invention, FIG. 2 is a partial schematic perspective view of the electrode manufacturing apparatus, and FIG. 3 is an enlarged perspective view of a backup roll unit. However, FIG. 2 shows only a part of the current collector 14. FIG. 3 shows a state where the current collector 14 is removed.

  As shown in FIG. 1, the powdered positive electrode active material 2 is supplied to a hopper 3. The positive electrode active material 2 in the hopper 3 is supplied to the mixer 4 by a conveying means (not shown). The mixer 4 disperses and stirs the powdered positive electrode active material 2 and the solvent to form a slurry 5. The slurry 5 that is a mixture of the positive electrode active material 2 and the solvent produced by the mixer 4 is hereinafter referred to as “active material slurry”.

  The electrode forming means includes a coating means for applying the active material slurry to the current collector 14 and an electrode drying means for drying the applied active material. The active material slurry 5 is supplied to a die coater 8 as a coating means via a conveying pipe 6 by driving a slurry conveying means such as a pump 7. Although only the die head 9 of the die coater 8 is shown in FIGS. 1 to 3, the die coater 8 extrudes the active material slurry 5 as a coating liquid from the die head 9 to form a film-like (plate-like) positive electrode current collector ( Hereinafter, it is also simply referred to as “current collector”). That is, the tip of the die head 9 is provided close to the current collector 14 wound around the peripheral surface of the backup roll 12. A slit 9 a is formed at the tip of the die head 9 in the horizontal direction. The active material slurry 5 is supplied from the slit 9 a toward the current collector 14, and the active material slurry 5 is applied onto the current collector 14. Since the backup roll 12 rotates in one direction (clockwise in the figure) at a constant speed, the active material slurry 5 having a predetermined thickness is applied on the current collector 14. Hereinafter, the active material slurry 5 applied on the current collector 14 is also referred to as a “coating film”.

  The coating means is not limited to that shown in FIGS. For example, FIG. 8 is a schematic configuration diagram of the electrode manufacturing apparatus of the second embodiment, which replaces FIG. 1 of the first embodiment.

  In the second embodiment, a gravure cylinder is used as a coating means. That is, in FIG. 8, the circumferential surface of the cylindrical or columnar gravure roll 51 is provided immediately below the backup roll 12 in proximity to the current collector 14 wound around the circumferential surface of the backup roll 12. The axis of the gravure roll 51 is made parallel to the axis of the backup roll 12.

  In addition, the active material slurry 5 is supplied to a predetermined height in the tub 52 through the conveying pipe 6 by the pump 7, and the lower part of the gravure roll 51 is immersed in the liquid of the active material slurry 5 in the tub 52. . For this reason, when the gravure roll 51 is rotated counterclockwise while the backup roll 12 is rotated in the clockwise direction, the active material slurry 5 is wound on the peripheral surface of the gravure roll 51 and the gravure roll 51 is backed up. The active material slurry 5 is applied (transferred) to the current collector 14 at a predetermined thickness at a portion facing the roll 12.

  The active material slurry 5 applied on the current collector 14 forms a positive electrode active material layer after drying. Thus, after the coating film is dried, a positive electrode is formed from the current collector 14 and the dried coating film 15 (that is, the positive electrode active material layer).

  The current collector transport means includes a feed roll 11, a backup roll 12, and a take-up roll 13 as shown in FIGS. 1 and 8. In FIG. 8, an idler 53 is added. The feed roll 11, the backup roll 12, and the take-up roll 13 (and the idler 53) arranged so that the axes are parallel to each other in the horizontal direction are all cylindrical or columnar, and the rolls 11 to 13 and the idler 53 are A current collector 14 having a predetermined width is wound around. The current collector 14 is conveyed from the feed roll 11 to the backup roll 12 by rotating the take-up roll 13 in the clockwise direction in FIGS. 1 and 8, and then taken up by the take-up roll 13. After the current collector 14 passes through the die head 9 and the gravure roll 51, a coating film 15 having a predetermined thickness is applied on the current collector 14.

  Now, a lithium ion battery is finally manufactured using the electrode manufactured by the electrode manufacturing apparatus shown in FIG. 1 or FIG. 4 and 5 described later show one cell 31 included in the lithium ion battery. If metal particles are contained in the active material slurry 5 or metal particles are mixed in the electrode manufacturing process, the metal particles may elute and precipitate in the cell 31 and the battery may cause an internal short circuit (self-discharge). is there. Unlike consumer batteries, automobile batteries have the characteristics of a long life cycle and the characteristics of a large short-circuit current when an internal short circuit occurs, so when adopting a lithium ion battery as an automobile battery, Measures against foreign metal particles are important.

  For this reason, in the conventional electrode manufacturing apparatus, the positive electrode active material transport pipe is formed of a magnetic material before the active material slurry is formed, and a magnetic field is applied to the transport pipe to trap the foreign metal particles in the transport pipe. This prevents the foreign metal particles contained in the positive electrode active material from being contained in the manufactured electrode (battery).

  However, in the conventional electrode manufacturing apparatus, if the metal foreign particles are small, the amount of magnetization of the metal foreign particles is also small, so the metal foreign particles are not stably adsorbed on the conveying pipe and the metal foreign particles still remain in the positive electrode active material. There is a fear. Therefore, when manufacturing the battery, there is a possibility that the metal foreign matter will be deposited and grown on the local part of the separator, causing an internal short circuit. In addition, when metal foreign particles are deposited on a transfer pipe that is a magnetic field application unit, there is a problem that the ability to remove the metal foreign particles decreases. If the deposited foreign metal particles are periodically collected, the operating rate of battery production deteriorates.

  Therefore, in the present invention, the metal foreign particles are not completely removed from the positive electrode active material, but self-discharge is performed after the battery is completed by controlling the position of the metal foreign particles contained in the positive electrode active material at the time of manufacturing the electrode. Prevent it from happening. If self-discharge can be prevented, the yield of the electrode is improved.

  Details will be described below. 1 and 8, the backup roll 12 is made of a magnetic material such as iron or SUS, and the magnetic material backup roll 12 is excited by a magnet such as a permanent magnet, an electromagnet, or a superconducting magnet. For example, a plurality of short columnar parts having an axial height of about 10 mm are formed with SUS420, the short columnar parts are arranged coaxially, and a nonmagnetic material is sandwiched between adjacent short columnar parts to form a single piece as a whole. A cylindrical composite is formed. And the one backup roll 12 extended in an axial direction is produced by coat | covering the surface of this composite_body | complex with engine plastic resin.

  In order to make it possible to adjust the magnitude of the magnetic field applied to the backup roll 12, an electromagnetic wave composed of a rectangular parallelepiped iron core 22 and an insulating winding 23 is formed on the outer periphery in the axial direction of the backup roll 12 as shown in FIG. 3. The coils 21 are arranged side by side along the axial direction of the backup roll 12. The axial length of the iron core 22 (the axial direction of the backup roll 12) so that the two end portions 22a, 22b of the iron core 22 around which the winding 23 is not wound protrude from the axial ends 12a, 12b of the backup roll 12. Is longer than the axial length of the backup roll 12. A rectangular parallelepiped shape is in contact with one axial end of the backup roll 12, that is, the axial end 12a located on the left front side in FIG. 3 and the side surface of the iron core 22 on the end 22a side located on the left front side in FIG. The first magnetic material 24 is disposed. Similarly, the other end of the backup roll 12 in the axial direction, that is, the axial end 12b located at the right rear side in FIG. 3 and the side surface of the iron core 22 at the end 22b side located at the right rear side in FIG. A rectangular parallelepiped second magnetic material 25 is disposed.

  In addition, in embodiment, although the iron core 22 and the two magnetic materials 24 and 25 are shown by the rectangular parallelepiped shape, each shape of the iron core 22 and the two magnetic materials 24 and 25 is not restricted to a rectangular parallelepiped shape. Further, the portion for supplying the active material slurry such as the die head 9 shown in FIG. 1 and the gravure roll 51 shown in FIG. 8 onto the current collector 14 is not excited and is made of a nonmagnetic material.

  When a current is passed through the electromagnetic coil 21, the electromagnetic coil 21 functions as an electromagnet. For example, as shown in FIG. 3, lines of magnetic force are generated in the iron core 22 in the axial direction of the backup roll 12. This magnetic field line bends in the second magnetic member 25 located at the right back, and enters the backup roll 12 from the other axial end 12 b of the backup roll 12. In the backup roll 12, the magnetic field lines are generated in the direction opposite to the iron core 22. The magnetic lines of force that have reached one axial end 12 a of the backup roll 12 bend in the first magnetic member 24 located on the left front side and return to the iron core 22. In this way, a loop of magnetic lines connecting the electromagnetic coil 21 and the backup roll 12 is formed (see arrow in FIG. 3).

  Thus, the magnetic field generating means is constituted by the electromagnetic coil 21, the backup roll 12, and the two magnetic materials 24 and 25.

  When magnetic lines of force are thus generated in the axial direction of the backup roll 12 by the electromagnetic coil 21, the individual short cylindrical parts forming the composite are magnetized. Since an S pole and an N pole are generated at the axial end of one short cylindrical part, FIG. 2 shows how magnetic poles are generated for two short cylindrical parts, and FIG. 3 shows how magnetic poles are generated for three short cylindrical parts. Yes. Actually, combinations of S poles and N poles are generated by the number of short cylindrical parts.

  Thus, by the backup roll 12 in which the individual short cylindrical parts are magnetized, the coating film 15 on the current collector 14 is changed from the surface of the coating film 15 (the surface exposed to the atmosphere) to the back surface of the coating film 15 (the surface exposed to the atmosphere). A line of magnetic force is generated in a direction toward the surface that is in contact with the current collector 14. The foreign metal particles in the coating film 15 are moved to the current collector 14 side by magnetic lines penetrating the coating film 15 from the front surface to the back surface.

  This will be described with reference to FIGS. The upper part of FIG. 4 and the upper part of FIG. 5 are cross-sectional views when the battery cells 31 are stacked. From the bottom, the current collector (positive electrode current collector) 14, the positive electrode active material layer 15 ′ (coating film 15), and the separator 16 are shown. The negative electrode active material layer 17 and the negative electrode current collector 18 are laminated in this order. A positive electrode is composed of the current collector (positive electrode current collector) 14 and the positive electrode active material layer 15 ′ (coating film 15), and a negative electrode is composed of the negative electrode active material layer 17 and the negative electrode current collector 18. In order to prevent the material layer 15 ′ and the negative electrode active material layer 17 from being short-circuited, a separator 16 as an insulating material is interposed between the electrodes. However, the separator 16 is configured to transmit ions such as metal ions. The electrode manufacturing apparatus shown in FIGS. 1 and 8 is an apparatus for manufacturing a positive electrode.

  In the upper part of FIG. 4 and the upper part of FIG. 5, one metal foreign particle M present in the positive electrode active material layer (coating film 15) is indicated by a circle. 4 shows a cell 31 in which metal foreign particles M exist in a position near the separator 16 in the positive electrode active material layer 15 ′ (coating film 15) by a conventional electrode manufacturing apparatus. On the other hand, the upper part of FIG. 5 is a cell 31 manufactured by the electrode manufacturing apparatus of the present invention, and the metal foreign particle M contained in the positive electrode active material layer 15 ′ (coating film 15) moves to a position close to the current collector 14. A cell 31 is shown.

  After the battery including the cell 31 is completed, the battery is charged and discharged. In this case, when an oxidation potential acts on the cell 31, the foreign metal particles M become metal ions M ′ in the positive electrode active material layer 15 ′ (coating film 15). Since the metal ion M ′ has a positive charge, it moves upward on the negative electrode current collector 18 side, that is, in FIGS. 4 and 5. In addition, the metal ion M ′ has a property of diffusing in a conical shape at an angle starting from the position where the metal foreign particle M is present. For this reason, as the distance from the position where the metal foreign particle M exists is increased, the metal ion M ′ spreads in the left-right direction, while the width in the vertical direction (movement direction) decreases. This is because the volume of the entire metal ion does not change.

  In the cell 31 produced by the conventional electrode manufacturing apparatus, as shown in the upper part of FIG. 4, the metal foreign particle M exists in the positive electrode active material layer 15 ′ (coating film 15) at a position close to the separator 16. Metal ions M ′ generated by the action of the oxidation potential diffuse upward. Since the position of the metal foreign particle M is close to the separator 16, the metal ion M ′ reaches the lower surface of the negative electrode active material layer 17 through the separator 16 before spreading in the left-right direction, as shown in the lower part of FIG. 4. . That is, since the metal ions M ′ do not spread in the left-right direction but remain in a long lump state in the up-down direction, the positive electrode active material layer 15 ′ and the negative electrode active material layer 17 are electrically connected and short-circuited by the metal ions M ′. End up.

  On the other hand, in the cell 31 created by the electrode manufacturing apparatus of the present invention, the metallic foreign particles M are moved to the vicinity of the current collector 14 as shown in the upper part of FIG. Even if the metal ion M ′ generated by the action of the oxidation potential diffuses upward, the position from the position where the metal foreign particle M is present to the lower surface of the separator 16 is farther from the upper stage of FIG. 4. Therefore, the metal ion M ′ penetrates the separator 16 and reaches the lower surface of the negative electrode active material layer 17 at a stage where the metal ion M ′ is greatly spread in the left-right direction, as shown in the lower part of FIG. That is, since the metal ions M ′ have spread greatly in the left-right direction, the vertical width is in a state thinner than the thickness of the separator 16. Therefore, if the metal ions M ′ are thin in the vertical direction, the positive electrode active material layer 15 ′ (coating film 15) and the negative electrode active material layer 17 are not electrically connected to each other depending on the metal ions M ′. Short circuit can be avoided.

  4 and 5, the viscous resistance of the coating film 15 (that is, the active material slurry) acting on the metal foreign particle M is not considered. Next, the viscous resistance of the active material slurry acting on the metal foreign particle M is not considered. Is considered. That is, when the metal foreign particle M is moved to the current collector 14 side by a magnetic force, a drag force (viscosity resistance) acts in a direction that prevents the movement of the metal foreign particle M (that is, the surface side of the coating film 15). To do. Therefore, when the magnetic force is Fm and the drag force is Fd, it is necessary to apply the magnetic force Fm to the metal foreign particle M so that the magnetic force Fm is larger than the drag force Fd.

Here, the magnetic force (hereinafter simply referred to as “magnetic force”) Fm acting on the metallic foreign particle M is:
Fm = VMΔH (1)
V: volume of foreign metal particles,
M: volume saturation magnetization of foreign metal particles,
ΔH: magnetic field gradient,
The drag force acting on the metal foreign particle M (hereinafter simply referred to as “drag force”) Fd
Fd = 6πrηvp (2)
Where r: radius of the foreign metal particle,
η: viscosity of the coating film (active material slurry),
vp: moving speed of foreign metal particles in the coating film (active material slurry),
It can be calculated by the following formula.

  For example, the radius r of the metallic foreign particle M is 100 [μm], the viscosity η of the coating film (active material slurry) is 10,000 [mPa · s], and the moving speed vp of the metallic foreign particle M in the coating film (active material slurry). Is 0.02 [mm / sec], the drag force Fd = 3.8 × 10 ^ −8 [N] from the above equation (2). However, “^” represents a power.

  In order to apply the magnetic force Fm that overcomes the drag force Fd, in the present invention, the maximum magnetic field strength T = 10 [T] and the magnetic field gradient ΔH = 1000 [T / m] are applied to the coating film 15 using the electromagnetic coil 21. Give. When the values of the maximum magnetic field strength T and magnetic field gradient ΔH are substituted into the above equation (1) and calculated, the magnetic force Fm = 4.1 × 10 ^ −8 [N] is obtained, and the minimum magnetism to overcome the drag force Fd The force Fm can be set.

The moving speed vp of the metallic foreign particle M of the above formula (2) is
vp = (distance traveled by the metal foreign particle M) /
(Time when the metal foreign particle M is exposed to the magnetic force Fm)
= (Distance from the lower surface of the positive electrode active material layer (15) to the lower surface of the negative electrode active material layer 17)
/ (Time for coating film 15 to pass through backup roll 12)
... (3)
It is a value defined by the formula.

  The magnetic field gradient ΔH in the formula (1) is simply the strength of the magnetic field in the environment where the metal foreign particle M is placed, and the density of magnetic flux generated from the surface of the coating film 15 toward the back surface of the coating film 15. This is a value obtained by dividing [T] by the distance [m] from the electromagnet (electromagnetic coil 21) to the metal foreign particle M. The volume saturation magnetization of the above formula (1) is a physical quantity indicating the degree of magnetization of the magnetic material, and is determined in advance depending on the type of the magnetic material.

  Next, how much the magnetic force Fm is set will be further described. Each particle L of the positive electrode active material dispersed and present in the coating film 15 has a little magnetism. Although the positive electrode active material particles L have a saturation magnetization amount as small as about 1/5 or less compared to the metal foreign matter particles M such as SUS, when the magnetic force Fm is too large, the magnetic force Fm is different from each particle of the positive electrode active material. Also acting on L, each particle L of the positive electrode active material is moved toward the current collector 14, and the positive electrode active material particles L are unevenly distributed in the coating film 15.

  This will be described with reference to FIG. The coating film 15 contains positive electrode active material particles L, metal foreign matter particles M, and particles N of other substances (for example, binder). Here, it is assumed that the positive electrode active material particles L, the foreign metal particles M, and the other material particles N are all spherical.

  The upper part of FIG. 6 shows how the state in the coating film 15 is before the magnetic force Fm is applied. The positive electrode active material particles L, the metal foreign particle M, and the particles N of other substances (for example, binder) are almost uniform. Scattered around. On the other hand, what happens to the state in the coating film 15 when the magnetic force Fm is too large is shown in the middle part of FIG. 6, and what happens to the state in the coating film 15 when the magnetic force Fm is appropriate is shown in the lower part of FIG. ing.

  Ideally, in the state where the positive electrode active material particles L are evenly dispersed in the coating film 15, only the metal foreign particles M are attracted by the magnetic force Fm and move closer to the current collector 14 (downward in the figure). It is to be. However, when the magnetic force Fm is too large, not only the metal foreign particles M but also the positive electrode active material particles L move to the vicinity of the current collector 14 due to the magnetic force Fm as shown in the middle part of FIG. In the coating film 15, the positive electrode active material particles L are unevenly distributed on the current collector 14 side.

  On the other hand, when the magnetic force Fm is set not to be strong or weak but optimally set, as shown in the lower part of FIG. Only the particles M can be moved close to the current collector 14. In order to optimize the magnetic force Fm as described above, the specification of the electromagnetic coil 21 is actually determined so that the range of the applied magnetic field can be adjusted to 0.5 to 10 [T].

  Returning to FIGS. 1 and 8, the current collector 14 moves between the backup roll 12 and the take-up roll 13 in order to dry the coating film 15 on the current collector 14 to form the positive electrode active material layer 15 ′. Are provided with a plurality of rows of heaters 41 and 42 as electrode drying means. Specifically, two rows of heaters 41 and 42 are provided in the moving direction of the current collector 14, and three heaters are provided in one row. The number of rows of heaters 41 and 42 and the number of heaters in one row are not limited to this.

  Flat permanent magnets 45, 46, 47 (magnetic field generating means) are provided close to the current collector 14 on the side opposite to the heaters 41, 42 across the current collector 14 (vertically below the current collector 14). It is arranged. The shape of the permanent magnets 45 to 47 is not limited to a flat plate shape, and may be a rod shape. In FIG. 1 and FIG. 8, three permanent magnets 45 to 47 are arranged in the moving direction of the current collector 14, but at least one permanent magnet row (number) is sufficient. Further, it may be an electromagnet instead of a permanent magnet.

  1 and 8, the permanent magnet 45 is brought close to the backup roll 12, but actually, the electromagnetic coil 21 shown in FIG. 3 exists between the backup roll 12 and the permanent magnet 45. .

  The reason why the heaters 41 and 42 and the permanent magnets 45 to 47 are arranged with the current collector 14 coated with the coating film 15 interposed therebetween is as follows. That is, heat is applied to the surface of the coating film 15 by the heaters 41 and 42, and from the surface of the coating film 15 to the back surface of the coating film 15 (the surface where the coating film 15 is in contact with the current collector 14) by the permanent magnets 45 to 47. This is because the coating film 15 is dried and the metal foreign particle M is moved toward the current collector 14 at the same time by applying a magnetic field so that magnetic field lines are generated in the direction toward the surface. The functions of the permanent magnets 45 to 47 are the same as the functions of the electromagnet provided to the backup roll 12.

  This will be further described with reference to FIG. The coating film 15 contains positive electrode active material particles L, metal foreign matter particles M, and particles N of other substances (for example, binder). Here, the positive electrode active material particles L and the other material particles N are spherical, whereas the metal foreign particle M is shown in a star shape.

  The state in the coating film 15 before the magnetic force Fm from the permanent magnets 45 to 47 acts is shown in the upper part of FIG. 7 after passing through the heaters 41 and 42 and the permanent magnets 45 to 47 (that is, the coating film). FIG. 7 shows the state of the state in the coating film 15 after 15). In addition, the upper stage of FIG. 7 does not show the state in the coating film 15 after passing through the backup roll 12. In other words, the state in the coating film 15 when the electromagnetic coil 21 is not energized and before the permanent magnets 45 to 47 is shown.

  As shown in the upper part of FIG. 7, the moving speed of the metal foreign particles M (see arrow) is about 5 times faster than the moving speed of the positive electrode active material particles L (see arrow). As shown in the lower part of FIG. 7, the metal foreign particle M is not included in the area surrounded by the broken line. Thus, the positive electrode active material particles L are unevenly distributed on the current collector 14 side in the coating film 15 by simultaneously drying the coating film 15 and moving the metal foreign particle M to the current collector 14 side. Can be dried and fixed. Thereby, segregation of the positive electrode active material particles L can be reduced.

  Here, the effect of this embodiment is demonstrated.

  According to this embodiment, the metal foreign particles in the active material slurry 5 applied to one surface of the current collector 14 are attracted to the current collector 14 side by the magnetic field generated by the electromagnetic coil 21 and the backup roll 12. The foreign metal particles can be selectively arranged on the current collector 14 side. Therefore, when the battery is manufactured, the metal foreign particles are located at a position far from the separator 16, so that the metal foreign particles are changed to metal ions by charging / discharging after the battery manufacture, and the metal ions are separated from the separator 16 side. In the process of moving to (the side opposite to the current collector 14), the metal foreign particles are diffused more than when the particles are present at a position close to the separator 16. The internal short circuit can be suppressed by the difference in the degree of diffusion.

  Specifically, when an oxidation voltage is applied to the cell 31, the distance from the separator 16 is longer than the case where the metal foreign particle M is present near the surface of the coating film 15 (on the surface side), and the distance is increased. When metal ions M ′ that change from the foreign metal particles M move toward the negative electrode active material layer 17 (upward in the lower part of FIG. 5), the diffusion range in the direction perpendicular to the moving direction (left and right in the lower part of FIG. 5) And the width in the moving direction becomes thin, so that the situation where the positive electrode active material layer 15 ′ and the negative electrode active material layer 17 are short-circuited by the metal ions M ′ diffused in the separator 16 can be avoided (FIG. 5). See below).

  According to the present embodiment, the magnetic field generating means is provided on the back surface of the coating film 15 (active material slurry) applied to the current collector 14 from the surface of the coating film 15 (active material slurry) applied. Since the lines of magnetic force are generated in the direction toward, the metal foreign particles can be moved to the current collector 14 side.

  According to this embodiment, since the backup roll 12 (current collector transporting means) functions as an electromagnet (having a magnetic field generating means), the electrode manufacturing apparatus 1 can be made compact.

  According to the present embodiment, the heaters 41 and 42 (electrode drying means) for drying the active material slurry applied to one surface of the current collector 14 are included, and the coating film (active material slurry) 15 is applied. Permanent magnets 45 to 47 (second magnetic field generating means) are arranged on the side opposite to the heaters 41 and 42 across the current collector 14. That is, the surface of the coating film (active material slurry) 15 on the current collector 14 is dried, and simultaneously, a magnetic field is applied from the back surface (current collector 14 side) of the coating film 15 by the permanent magnets 45 to 47. Drying and magnetic attraction of the foreign metal particles toward the current collector 14 can be performed simultaneously. Since the foreign metal particles have a higher moving speed than the active material particles, the active material particles are scattered in the coating film 15 by magnetic attraction and drying of the foreign metal particles simultaneously, and the active material particles are not unevenly distributed. It can be dried and fixed as a layer (see the lower part of FIG. 7).

  In the first and second embodiments, the backup roll 12 is made to function as an electromagnet (magnetic field generating means), and the permanent magnets 45 to 47 are provided as magnetic field generating means, that is, two magnetic field generating means are provided. However, the mode (3rd Embodiment) which does not provide the function as an electromagnet to the backup roll 12, ie, uses one magnetic field generation | occurrence | production means can be considered. When a strong magnetic field is applied too much by the backup roll 12 before the coating film 15 is dried, the positive electrode active material particles may be unevenly distributed on the current collector 14 side in the coating film 15, but the third embodiment. According to the present invention, since the coating film 15 is dried immediately after the foreign metal particles move to the current collector 14 side in the coating film 15, it is avoided that the positive electrode active material particles are unevenly distributed on the current collector 14 side. it can.

  In the embodiment, the case where the active material slurry is the positive electrode active material slurry has been described, but the present invention can also be applied when the active material slurry is the negative electrode active material slurry.

DESCRIPTION OF SYMBOLS 1 Electrode manufacturing apparatus 5 Active material slurry 8 Die coater (electrode formation means)
9 Die head 11 Feed roll (conveying means)
12 Backup roll (conveying means, magnetic field generating means)
13 Winding roll (conveying means)
14 Current collector (current collector)
21 Electromagnetic coil (magnetic field generating means)
41, 42 Heater (electrode drying means)
45, 46, 47 Permanent magnet (magnetic field generating means)
51 Gravure roll (electrode forming means)

Claims (9)

Current collector transport means for moving the current collector;
An electrode forming means for forming an electrode by applying an active material slurry to one surface of the current collector to form an active material layer;
And a magnetic field generating means for applying a magnetic field to the active material slurry applied to the current collector from the other surface side of the current collector to which the active material slurry is applied. The electrode manufacturing apparatus according to claim 1,
The magnetic field generating means generates a magnetic field line in a direction from the surface of the applied active material slurry to the back surface of the active material slurry applied to the current collector. Electrode manufacturing equipment. In the electrode manufacturing apparatus according to claim 1 or 2,
The electrode manufacturing apparatus, wherein the current collector conveying means has a magnetic field generating means. In the electrode manufacturing apparatus according to any one of claims 1 to 3,
An electrode drying means for drying the active material slurry applied to one surface of the current collector,
An apparatus for producing an electrode, wherein the magnetic field generating means is arranged on the opposite side of the electrode drying means across a current collector coated with an active material slurry. An electrode forming step of forming an electrode by applying an active material slurry to one surface of a plate-like current collector to form an active material layer;
And a magnetic field generating step of applying a magnetic field to the active material slurry applied to the current collector from the other surface side of the current collector to which the active material slurry is applied. In the electrode manufacturing method according to claim 5,
An electrode manufacturing method comprising applying an active material slurry to one surface of the current collector and simultaneously applying a magnetic field to the active material slurry applied to the current collector. In the electrode manufacturing method according to claim 5 or 6,
The magnetic field is applied to the applied active material slurry from the side of the other surface of the current collector on which the active material slurry is applied while drying the active material slurry applied to one surface of the current collector. The electrode manufacturing method characterized by the above-mentioned.   The electrode manufactured by the electrode manufacturing apparatus or electrode manufacturing method as described in any one of Claim 1-7.   The lithium ion battery using the electrode manufactured by the electrode manufacturing apparatus or electrode manufacturing method as described in any one of Claim 1-7.