JP2016004743A - Electrode manufacturing device and electrode manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide electrode manufacturing device and method that can suppress formation of an impression on a press roll.SOLUTION: A roll press device 1 has plural press roll pairs 2 passing through a belt-like metal foil 12 on which an active material layer 13 is formed. The plural press roll pairs 2 have first press roll pairs 3A, 3B which are configured so that the roll intervals d1, d2 are set to be equal to or more than the total thickness b of the metal foil 12 and the active material layer 13 before pressing, and second press roll pairs 3C which are arranged at the rear stage side of the first press roll pairs 3A, 3B and configured so that the roll interval d3 is set to be less than the total thickness b of the metal foil 12 and the active material layer 13 before pressing.

Description

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

  In the manufacturing process of electrodes used in secondary batteries, for example, an electrode paste is applied to a strip-shaped metal foil to form an active material layer, and individual electrodes are formed from the strip-shaped metal foil on which the active material layer is formed. A punching process is included. In this step, after the active material layer is formed on the strip-shaped metal foil, the active material layer may be pressed by, for example, a roll press device in order to increase the density of the active material.

  In a roll press apparatus, a band-shaped metal foil on which an active material layer is formed is sandwiched between a pair of press rolls, and the active material layer is pressed by these press rolls (see, for example, Patent Document 1). Some roll press apparatuses include a plurality of pairs of press rolls. In such a roll press apparatus, the active material layer is pressed stepwise by a plurality of pairs of press rolls (see, for example, Patent Documents 2 and 3).

JP 2013-223871 A JP 2010-80272 A JP 58-97268 A

  The active material layer formed on the metal foil may have a convex portion on the surface due to, for example, aggregation of the active material. When the active material layer is pressed in a state where the convex portion is generated, a local load is applied to the press roll by the convex portion, and an indentation may be formed on the press roll. If indentations are formed on the press roll, the film thickness of the active material layer may be nonuniform during subsequent pressing. There is also a problem that the frequency of replacing the press roll is increased.

  The present invention has been made to solve the above problems, and an object of the present invention is to provide an electrode manufacturing apparatus and an electrode manufacturing method capable of suppressing the formation of indentations on a press roll.

  In order to solve the above problems, an electrode manufacturing apparatus according to one aspect of the present invention includes a plurality of press roll pairs through which a strip-shaped metal foil on which an active material layer is formed, and the plurality of press roll pairs includes: The first press roll pair in which the roll interval is set so as to be equal to or greater than the total thickness of the metal foil and the active material layer before pressing, and the metal before pressing, arranged on the rear stage side of the first press roll pair And a second press roll pair in which the roll interval is set to be less than the combined thickness of the foil and the active material layer.

  In this electrode manufacturing apparatus, when a protrusion due to, for example, active material aggregation occurs on the surface of the active material layer formed on the metal foil, only the protrusion is formed into a press roll by the first press roll pair. It becomes possible to make it contact. Before the active material layer is pressed by the second press roll pair, the convex portion is flattened by bringing only the convex portion into contact with the press roll by the first press roll pair. Load can be relaxed and the formation of indentations on the press roll can be suppressed.

  Further, the first press roll pair may include a plurality of press roll pairs in which roll intervals are set so as to become narrower toward the rear stage side. In this case, since the convex portion is flattened in stages by the plurality of press roll pairs, the local load applied to the press roll can be more reliably alleviated. Therefore, it can suppress suitably that an indentation will be formed in a press roll.

  The electrode manufacturing method according to one aspect of the present invention includes a pressing step of pressing a band-shaped metal foil on which an active material layer is formed with a press roll pair, and the pressing step includes a metal foil and an active material layer before pressing. The first step of passing the metal foil and the active material layer through the first press roll pair in which the roll interval is set so as to be equal to or greater than the combined thickness, and the metal before pressing after performing the first step And a second step of passing the metal foil and the active material layer through a second press roll pair in which the roll interval is set to be less than the combined thickness of the foil and the active material layer.

  In this electrode manufacturing method, when the convex part resulting from aggregation of the active material etc. has arisen on the surface of the active material layer formed in metal foil, only a convex part is made into a press roll by the 1st press roll pair. It becomes possible to make it contact. Before the active material layer is pressed by the second press roll pair, the convex portion is flattened by bringing only the convex portion into contact with the press roll by the first press roll pair. Load can be relaxed and the formation of indentations on the press roll can be suppressed.

  Further, in the first step, the metal foil and the active material layer may be passed through a plurality of press roll pairs in which the roll interval is set so as to narrow toward the rear side. In this case, since the convex portion is flattened in stages by the plurality of press roll pairs, the local load applied to the press roll can be more reliably alleviated. Therefore, it can suppress suitably that an indentation will be formed in a press roll.

  According to this invention, it can suppress that an indentation is formed in a press roll.

It is the schematic which shows one Embodiment of the electrode manufacturing apparatus which concerns on this invention. It is a figure which shows an example of the relationship of the load in a press roll pair. It is the schematic which shows the press process by the electrode manufacturing apparatus shown in FIG. FIG. 5 is a schematic view showing a subsequent process of FIG. 4. FIG. 6 is a schematic diagram illustrating a subsequent process of FIG. 5.

  Hereinafter, preferred embodiments of an electrode manufacturing apparatus and an electrode manufacturing method according to the present invention will be described in detail with reference to the drawings.

  It is the schematic which shows one Embodiment of the electrode manufacturing apparatus which concerns on this invention.

  FIG. 1 is a configuration diagram showing an embodiment of an electrode manufacturing apparatus according to the present invention. The electrode manufacturing apparatus according to the present embodiment is configured as a roll press apparatus 1 used in a pressing process, which is a process for manufacturing an electrode of a secondary battery. The secondary battery is a nonaqueous electrolyte secondary battery such as a lithium ion secondary battery.

  The electrode of a secondary battery is comprised by the metal foil which makes a rectangle, for example, and the active material layer each formed in the front and back both surfaces of metal foil. The active material layer is formed by applying electrode paste to both the front and back surfaces of the metal foil. The electrode is also provided with a tab to which no electrode paste is applied.

  The metal foil of the positive electrode is, for example, an aluminum foil, and the metal foil of the negative electrode is, for example, a copper foil. The electrode paste contains an active material, a binder, a solvent, and the like. As the positive electrode active material, for example, composite oxide, metallic lithium, and sulfur are used. The composite oxide includes at least one of manganese, nickel, cobalt, and aluminum and lithium. Examples of the active material for the negative electrode include carbon such as graphite, highly oriented graphite, mesocarbon microbeads, hard carbon, and soft carbon, alkali metals such as lithium and sodium, metal compounds, and SiOx (0.5 ≦ x ≦ 1. 5) and other metal oxides and boron-added carbon are used. As the solvent, for example, organic solvents such as NMP (N-methylpyrrolidone), methanol, methyl isobutyl ketone, and water are used. Further, the electrode paste may contain a conductive additive such as carbon black, graphite, acetylene black, and ketjen black, and a thickener such as carboxymethyl cellulose (CMC).

  In addition, a coating process and a drying process are performed as a pre-process of a press process. The coating process is a process of coating an electrode paste for forming an active material layer on both surfaces of a strip-shaped metal foil. In the coating process, the electrode paste is applied to both surfaces of the strip-shaped metal foil with a predetermined interval. As the coating method, for example, a die method or a comma roll method is adopted. The drying step is performed immediately after the coating step, and is a step of removing the solvent in the electrode paste by heating and drying the electrode paste coated on both surfaces of the belt-shaped metal foil. As a result, a band-like electrode is obtained in which active material layers are formed at predetermined intervals on both sides of the band-like metal foil. The strip electrode is wound around a winding roll.

  In the subsequent pressing step, the unwinding roll and the take-up roll are operated so that the strip-shaped electrode is fed out from the unwinding roll, and the strip-shaped electrode and the unwinding roll at a predetermined transport speed in a state where a predetermined tension is applied. It is transported between winding rolls. When conveyance of the strip electrode is started, the roll press apparatus 1 of the present embodiment is operated.

  As shown in FIG. 1, the roll press apparatus 1 includes a plurality of pairs of upper and lower press roll pairs 2 (here, a pair of upper and lower press rolls 2 disposed so as to sandwich a strip electrode 11 conveyed between an unwind roll and a take-up roll. 3 pairs). The strip electrode 11 includes a strip-shaped metal foil 12 and an active material layer 13 formed on the front and back surfaces of the metal foil 12 with predetermined intervals. The active material layer 13 may be formed continuously or intermittently.

  In the present embodiment, the press roll pair 2 includes a first press roll pair 3A, 3B in which the roll interval is set to be equal to or greater than the combined thickness of the active material layer 13 and the metal foil 12 before pressing, A second press roll pair 3C, which is disposed on the rear side of the first press roll pair 3A, 3B, and the roll interval is set to be less than the combined thickness of the metal foil 12 and the active material layer 13 before pressing; Therefore, it has a three-stage configuration.

  The first press roll pair 3A, 3B is a press roll pair for flattening the protrusions 14 formed on the surface of the active material layer 13 before the active material layer 13 is pressed by the second press roll pair 3C. It is. The second press roll pair 3C is a press roll pair that sandwiches the active material layer 13 and performs pressing with a predetermined pressing pressure.

  The convex portion 14 of the active material layer 13 is an abnormal portion formed on the surface of the active material layer 13 due to, for example, aggregation of the active material or deviation of components in the electrode paste. The thickness of the strip electrode 11 including the convex portion 14 (the total thickness of the metal foil 12, the active material layer 13 on both sides of the metal foil 12, and the convex portion 14) is a, and the strip electrode not including the convex portion 14 11 (the total thickness of the metal foil 12 and the active material layer 13 on both surfaces of the metal foil 12) is b, and the target value of the thickness of the strip electrode 11 after pressing is c (see FIG. 5). Assuming that the roll intervals of the first press roll pair 3A, 3B and the second press roll pair 3C are d1 to d3, these satisfy the relationship of a> d1> d2 ≧ b> d3 = c. .

  In determining the roll intervals d1 and d2 according to the above relationship, it is necessary to determine the thickness a of the belt-like electrode including the convex portion 14. Since there are a plurality of causes for the convex portion 14, the thickness a is not generally determined to be a specific value. However, the cause is limited when the convex part 14 is scattered in each manufacturing apparatus (manufacturing line) like the adhesion of the aggregates mentioned later and the metal foreign material derived from a manufacturing apparatus. In this case, the thickness a can also be measured by a test, and the roll intervals d1 and d2 can be determined with the maximum value of the measured thickness as the thickness a.

  As an example, the thickness a of the strip electrode 11 including the convex portion 14 is 300 μm, the thickness b of the strip electrode 11 not including the convex portion 14 is 200 μm, and the target value of the thickness of the strip electrode 11 after pressing is 160 μm. In some cases, the roll interval d1 of the first press roll pair 3A is set to 220 μm, the roll interval d2 of the first press roll pair 3B is set to 200 μm, and the roll interval d3 of the second press roll pair 3C is set to 160 μm.

  When the convex portion 14 is formed by an agglomeration of active material, the thickness of the convex portion 14 is the thickness of the active material layer 13 before pressing (in the case of the die method, the nozzle interval of the die head, the comma roll method) In this case, the distance between the comma roll and the coating roll is considered to be less than or equal to. In this case, the upper limit value of the roll interval d1 of the first press roll pair 3A through which the strip electrode 11 first passes is twice the thickness of the metal foil 12 and the thickness of the active material layer 13 on both surfaces of the metal foil 12. And the total thickness.

  The press method using the press roll pair 2 is a fixed-size press method. In this case, as shown in FIG. 2, the load applied to one bearing portion 24 of the lower roll 22 is F1, the load applied to the other bearing portion 25 is F2, and the load applied to the strip electrode 11 from the lower roll 22 and the upper roll 23. Is F3, the load applied to one bearing portion 26 of the upper roll 23 is F4, and the load applied to the other bearing portion 27 is F5, the relationship of F1 + F2 = F3 + F4 + F5 is satisfied. When the strip electrode 11 passes without contacting the lower roll 22 and the upper roll 23, the load is received by the support portions 28 disposed between the bearing portions 24 and 26 and between the bearing portions 25 and 27. The pressing load of the strip electrode 11 and the temperature at the time of pressing can be arbitrarily set.

  In the roll press apparatus 1 having the above-described configuration, when the belt-like electrode 11 having the convex portions 14 formed on the surface of the active material layer 13 is conveyed, the belt-like electrode 11 is the first one as shown in FIG. When passing between the rolls of the press roll pair 3A, only the convex portion 14 comes into contact with the first press roll pair 3A, and the convex portion 14 is flattened at a certain level.

  More specifically, for example, when the convex portion 14 is caused by the agglomerates of the active material and is formed by protruding a part of the agglomerates from the inside of the active material layer 13 to the surface, the first press roll When the convex portion 14 comes into contact with the pair 3A, the aggregate that is the cause of the convex portion 14 is deformed so as to be crushed inside the active material layer 13, and the height of the convex portion 14 is reduced. At this time, when a high pressure from the pair of press rolls is also acting on the active material layer 13 around the convex portion 14 as in the case of performing pressing with a conventional roll press apparatus, the aggregation inside the active material layer 13 is performed. It is difficult for deformation and movement of the lump to occur, and a large force acts locally on the surface of the press roll contacting the convex portion 14.

  On the other hand, the press roll pair 3 </ b> A in the roll press apparatus 1 contacts only the convex portion 14 and the back surface side corresponding to the convex portion 14, and does not act on the active material layer 13 around the convex portion 14. Therefore, deformation of the agglomerates in the active material layer 13 is likely to occur, and the burden on the press roll pair 3A is reduced. Even when the convex portion 14 is caused by another cause (for example, adhered foreign matter) and moves so as to sink into the active material layer 13 by contact with the press roll pair 3A, the flattening is similarly facilitated.

  When the belt-like electrode 11 is further conveyed to the rear stage side, as shown in FIG. 4, when the belt-like electrode 11 passes between the rolls of the first press roll pair 3B, only the convex portion 14 is the first press roll pair 3B. And the convex portion 14 is further flattened. Therefore, as shown in FIG. 5, the active material layer 13 can be pressed by the second press roll pair 3 </ b> C in a state where the convex portions 14 on the surface of the active material layer 13 are flattened. Thus, by flattening the convex portion 14 before pressing the active material layer 13, a local load applied to the second press roll pair 3C can be relaxed, and an indentation is formed on the second press roll pair 2C. Can be suppressed.

  The roll press apparatus 1 includes two stages of first press roll pairs 3A and 3B in which the roll interval is set so as to become narrower toward the rear stage side. Therefore, since the convex portion is flattened stepwise by the first press roll pair 3A, 3B, the local load applied to the second press roll pair 3C can be more reliably alleviated. Therefore, it can suppress suitably that an indentation is formed in the 2nd press roll pair 3C.

  In the present embodiment, the first press roll has two stages, but the first press roll may have only one stage or three or more stages. In the present embodiment, the second press roll has one stage, but the second press roll may have multiple stages.

  DESCRIPTION OF SYMBOLS 1 ... Roll press apparatus (electrode manufacturing apparatus), 2 ... Press roll pair, 3A, 3B ... 1st roll press pair, 3C ... 2nd roll press pair, 12 ... Metal foil, 13 ... Active material layer.

Claims (4)

Provided with a plurality of press roll pairs through which a band-shaped metal foil with an active material layer formed passes between,
The plurality of press roll pairs are:
A first press roll pair in which the roll interval is set to be equal to or greater than the combined thickness of the metal foil and the active material layer before pressing;
A second press roll pair disposed on the rear side of the first press roll pair and having a roll interval set so as to be less than the combined thickness of the metal foil and the active material layer before pressing. Including electrode manufacturing equipment.   The electrode manufacturing apparatus according to claim 1, wherein the first press roll pair includes a plurality of press roll pairs in which a roll interval is set so as to become narrower toward a rear stage side. A pressing step of pressing the band-shaped metal foil on which the active material layer is formed with a press roll pair;
The pressing step includes
A first step of passing the metal foil and the active material layer through a first press roll pair in which a roll interval is set to be equal to or greater than the combined thickness of the metal foil and the active material layer before pressing;
After performing the first step, the metal foil and the active foil are placed on a second press roll pair in which a roll interval is set to be less than the combined thickness of the metal foil before pressing and the active material layer. And a second step of passing the material layer.   The electrode manufacturing method according to claim 3, wherein, in the first step, the metal foil and the active material layer are passed through a plurality of press roll pairs in which roll intervals are set so as to narrow toward the rear side.

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