JP2014078439A - Electrode manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode manufacturing method capable of forming a flat plane-like active material layer.SOLUTION: A positive electrode manufacturing method has: a coating step of coating an active material mixture on both faces of a metallic foil 22 for a positive electrode at an interval in a longitudinal direction of the metallic foil 22 for the positive electrode to form coating parts G, and forming an un-coated part M between the adjacent parts G in the longitudinal direction; and a press step of pressing the coating parts G. Furthermore, the positive electrode manufacturing method has: a support layer forming step performed after the press step and for providing a support layer 40 in the un-coated part M; and a take-up step of taking up the metallic foil 22 for the positive electrode after the support layer forming step around a take-up roll 46 for firing in the longitudinal direction.

Description

  The present invention relates to an electrode manufacturing method including an active material layer on at least one surface of a metal foil.

  A vehicle such as an EV (Electric Vehicle) or a PHV (Plug in Hybrid Vehicle) is equipped with a secondary battery such as a lithium ion battery as a power storage device that stores electric power supplied to the electric motor. This type of secondary battery has a positive electrode and a negative electrode having an active material layer on a metal foil, an electrode assembly in which a positive electrode and a negative electrode are laminated with a separator therebetween, and an electrode assembly. Is housed in a case together with an electrolytic solution.

  The active material layer is formed by applying a slurry-like or paste-like active material mixture containing an active material to a metal foil, and drying and curing (see, for example, Patent Document 1). In the manufacturing method of the electrode plate for nonaqueous electrolyte secondary batteries of patent document 1, the easily peelable tape which has an adhesive layer on a base | substrate in the longitudinal direction on the electrical power collector which consists of elongate metal foil. And an active material mixture is applied on the current collector excluding the easily peelable tape to form an active material layer. Next, the easily peelable tape and the active material layer on the current collector are pressed so that the thickness of the easily peelable tape is the same as that of the active material layer. And if an easily peelable tape is peeled, an uncoated part will be formed on an electrical power collector between an active material layer and an adjacent active material layer. The electrode metal foil on which the active material layer and the uncoated portion are formed is wound into a roll.

JP 2005-216722 A

  However, when the electrode metal foil is wound into a roll, another active material layer is superimposed on the wound active material layer. At this time, another active material layer overlapped with the wound active material layer is pushed toward the wound active material layer by the weight of the stacked electrode metal foil or the like. Then, another active material layer that protrudes from the wound-up active material layer is bent so as to fall into the uncoated portion. As a result, a winding mark formed when the active material layer is bent is attached, and the active material layer is formed in an uneven shape.

  It is an object of the present invention to provide an electrode manufacturing method capable of forming a flat surface active material layer.

  In order to solve the above problems, the invention described in claim 1 is a method of manufacturing an electrode including an active material layer on at least one side of a metal foil, wherein an active material mixture containing an active material is used as a strip-shaped metal. At least one surface of the foil is coated with an interval along the longitudinal direction of the metal foil to form a coating portion, and the active material mixture is formed between the coating portions adjacent to each other in the longitudinal direction. An application process for forming an uncoated part that is not coated, a pressing process for pressing the coated part, and a support layer made of a material different from the coated part on the uncoated part. And a winding step of winding the belt-shaped metal foil after the supporting layer forming step on a winding roll along the longitudinal direction.

  According to this, the coated portion is slightly restored in the thickness direction after being compressed in the thickness direction by the pressing process. Since the support layer is formed on the uncoated part after this pressing step, the thickness of the support layer can be adjusted to the thickness of the coated part whose thickness has been restored. And in a winding process, another coating part is piled up directly or indirectly on both sides of the said metal foil with respect to the coating part already wound by the winding roll. At this time, another coating portion that overlaps the wound coating portion is pushed toward the winding roll by the weight of the metal foil that is overlapped and the winding of the metal foil. Then, another coating portion that protrudes from the wound coating portion tends to fall toward the winding roll. However, a support layer is provided in front of the collapse. And since the thickness of a support layer is match | combined with the thickness of the restored coating part, another pressed coating part is supported by the support layer, without falling down. As a result, in the longitudinal direction of the metal foil, it is suppressed that another coating part is bent from the edge of the wound coating part, and the winding mark is prevented from sticking to another coating part. . As a result, it is possible to prevent unevenness from being formed in the coated portion, and to form a flat active material layer.

Moreover, the thickness of the said support layer may be the same as the thickness of the said coating part after the said press process.
According to this, since the support layer and the coating part have the same thickness, even if another coating part is pushed toward the take-up roll, the other coating part does not bend into the support layer. Can be supported.

Moreover, the said support layer may be provided over the whole length of the said uncoated part along the longitudinal direction of the said metal foil.
According to this, in the longitudinal direction of the metal foil, a continuous surface is formed without forming a step between the support layer and the coating portion. Therefore, when another coating part is pushed toward the winding roll, the other coating part protruding from the wound coating part is supported by the support layer from one end to the other end. For this reason, it is possible to reliably prevent the wound coating portion from falling down.

Moreover, it has the baking process of the said coating part after the said winding-up process.
According to this, the metal foil wound on the winding roll in the winding process is subjected to the firing process while being wound. And even during the firing process, the coated part is supported by the support layer, so even if baked and cured, the coated part remains flat without forming irregularities. Can do.

  According to the present invention, a flat active material layer can be formed.

The disassembled perspective view which shows the secondary battery of embodiment. The perspective view which shows the external appearance of a secondary battery. The perspective view which shows the component of an electrode assembly. (A) is a figure which shows an application | coating process and a drying process typically, (b) is a partial top view of the metal foil for positive electrodes which shows a coating part and an uncoated part. (A) is a figure which shows typically the state which winds up metal foil on a press process and the winding roll for baking, (b) is a partial top view of the metal foil for positive electrodes which shows a support layer and a coating part. The figure which shows the coating part and support layer of metal foil for positive electrodes set to the baking path. The figure which shows a punching process.

Hereinafter, an embodiment embodying the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, in a secondary battery 10 as a power storage device, an electrode assembly 14 is accommodated in a case 11. The case 11 has a rectangular parallelepiped main body member 12 and a rectangular flat plate-like lid member 13. The main body member 12 has a housing portion S inside thereof, and an insertion port 13c communicating with the housing portion S is opened. The lid member 13 closes the insertion port 13c. Both the main body member 12 and the lid member 13 constituting the case 11 are made of metal (for example, stainless steel or aluminum). Further, the secondary battery 10 of the present embodiment is a prismatic battery whose appearance is square. Further, the secondary battery 10 of the present embodiment is a lithium ion battery.

  A positive electrode terminal 41 and a negative electrode terminal 42 for taking out electricity from the electrode assembly 14 are electrically connected to the electrode assembly 14. The positive electrode terminal 41 and the negative electrode terminal 42 protrude out of the case 11 through the through hole 13a of the lid member 13, and the positive electrode terminal 41 and the negative electrode terminal 42 are ring-shaped insulation for insulation from the case 11. Each ring 13b is attached.

  As shown in FIG. 3, in the electrode assembly 14, a plurality of positive electrodes 21 as one electrode and a plurality of negative electrodes 24 as the other electrode can pass ions related to electrical conduction (lithium ions). The separators 27 are formed by alternately laminating with separators 27 formed of a porous film.

  The positive electrode 21 includes a rectangular positive electrode metal foil (in this embodiment, an aluminum foil) 22 and a rectangular positive electrode active material layer 23 provided on both surfaces (surfaces) of the positive electrode metal foil 22. Have. The positive electrode active material layers 23 on both surfaces of the positive electrode metal foil 22 have the same planar shape and the same thickness, and face each other with the positive electrode metal foil 22 interposed therebetween. The positive electrode 21 has a positive electrode-side inactive material layer portion 22d along which the positive electrode active material layer 23 is not provided. And in the positive electrode 21, the positive electrode current collection tab 31 protrudes in a part of one side of the positive electrode side inactive material layer part 22d.

  The negative electrode 24 includes a rectangular negative electrode metal foil (copper foil in this embodiment) 25 and a rectangular negative electrode active material layer 26 provided on both surfaces (surfaces) of the negative electrode metal foil 25. Have. The negative electrode active material layers 26 on both surfaces of the negative electrode metal foil 25 have the same planar shape and the same thickness. The negative electrode 24 has a negative electrode-side inactive material layer portion 25d along which the negative electrode active material layer 26 is not provided. And in the negative electrode 24, the negative electrode current collection tab 32 protrudes in a part of one side of the negative electrode side inactive material layer part 25d.

  As shown in FIG. 1, the positive electrode 21 and the negative electrode 24 are arranged such that the positive electrode current collecting tabs 31 are arranged in a line along the stacking direction, and the negative electrode current collecting tabs 32 are not overlapped with the positive electrode current collecting tabs 31. Are stacked in a row along the stacking direction. Each positive electrode current collecting tab 31 is bent in a state of being collected (bundled) within a range from one end to the other end in the stacking direction of the electrode assembly 14. Each positive current collecting tab 31 is electrically connected by welding a portion where each positive current collecting tab 31 overlaps, and a positive terminal 41 is connected to the positive current collecting tab 31. Each negative electrode current collection tab 32 is electrically connected by welding the location where each negative electrode current collection tab 32 has overlapped, and the negative electrode current collection tab 32 is connected to the negative electrode terminal 42.

  Next, a method for manufacturing the positive electrode 21 and the negative electrode 24 will be described. In addition, since the manufacturing method of the positive electrode 21 and the negative electrode 24 is fundamentally the same, the manufacturing method of the positive electrode 21 is demonstrated and the detailed description about the negative electrode 24 is abbreviate | omitted.

  The manufacturing method of the metal foil for positive electrode 22 includes an application process, a drying process, a cutting process, a pressing process, a support layer forming process, a winding process, a firing process, a removing process, and a punching process. Have.

First, the coating and drying apparatus 35 that performs the coating process and the drying process will be described.
As shown in FIG. 4A, the coating / drying device 35 applies the active material mixture to both sides of the supply mechanism 36 for supplying the metal foil 22 for the positive electrode and the metal foil 22 for the positive electrode. A coating mechanism 37 that forms the coating part G, a drying mechanism 38 that dries the coating part G, and a winding mechanism 39 that winds the positive electrode metal foil 22 after drying are provided. The supply mechanism 36 includes a supply roll 36a around which a long strip-shaped positive electrode metal foil 22 is wound in the longitudinal direction. The supply roll 36a is rotatably supported by a support mechanism.

  The coating mechanism 37 includes a first slit die 37 a, and the discharge port (not shown) of the first slit die 37 a is one surface that is the surface of the positive electrode metal foil 22 below the positive electrode metal foil 22. It is arranged opposite to (one side). The coating mechanism 37 includes a second slit die 37b. The discharge port (not shown) of the second slit die 37b is located on the other side, which is the surface of the positive electrode metal foil 22, above the positive electrode metal foil 22. Are arranged opposite to each other (one side).

  The active material mixture is intermittently discharged from the discharge ports of the first and second slit dies 37a and 37b, and the layers of the active material mixture are formed on both surfaces of the positive electrode metal foil 22 fed from the supply roll 36a. Are applied at intervals. Then, the layer of the coating part G is formed in both surfaces of the metal foil 22 for positive electrodes by each active material mixture. The lengths of the coating portions G along the longitudinal direction of the positive electrode metal foil 22 are all the same.

  As shown in FIG. 4B, the length of the coating part G along the short direction perpendicular to the longitudinal direction of the positive electrode metal foil 22 is also the same. That is, the same planar coated portions G are formed on both surfaces of the positive electrode metal foil 22 with a gap therebetween. The positive electrode active material mixture is a mixture of a positive electrode active material, a conductive additive, and a binder (binder), kneaded with a solvent. On the other hand, the negative electrode active material mixture is obtained by mixing a negative electrode active material, a conductive additive, and a binder (binder), adding a solvent, and kneading.

  Further, in the coating process, by intermittently discharging the active material mixture from the first and second slit dies 37a, 37b, between the coating parts G adjacent in the longitudinal direction of the positive electrode metal foil 22, An uncoated portion M where no active material mixture is applied is formed. Each uncoated part M is formed in a planar rectangular shape. In each uncoated portion M, the length N along the longitudinal direction of the positive electrode metal foil 22 is the same.

  As shown to Fig.4 (a), the drying mechanism 38 is provided with the dryer 38a which dries the coating part G with the heat from a heat source. The winding mechanism 39 includes a winding roll 39a for the drying mechanism. The drying mechanism winding roll 39a rotates at a constant rotation speed and winds up the positive electrode metal foil 22 fed from the supply roll 36a.

  In the coating process, the coating part G and the uncoated part M are formed on both surfaces of the positive electrode metal foil 22 by the coating mechanism 37. In the drying process, the coating part G applied to the positive electrode metal foil 22 by the drying mechanism 38 is dried. And the metal foil 22 for positive electrodes which passed the drying mechanism 38 is wound up by the winding roll 39a for drying mechanisms.

  In the cutting step, while winding the positive electrode metal foil 22 fed from the drying mechanism take-up roll 39a onto the firing take-up roll 46, both ends in the short direction (width direction) of the positive electrode metal foil 22 are formed. Disconnect. Further, as shown in FIG. 5 (a), in the pressing step, the positive electrode metal foil 22 immediately after the cutting step is sandwiched and pressed by rotating press rollers 63a and 63b. Each is compressed to a predetermined thickness.

  In the support layer forming step, after passing through the press rollers 63a and 63b, an adhesive tape made of a material different from the coated part G is attached to each uncoated part M, and the support layer 40 is formed with the adhesive tape. As shown in FIG.5 (b), the support layer 40 is stuck over the whole surface of the uncoated part M, and between the uncoated parts M adjacent in the longitudinal direction of the metal foil 22 for positive electrodes is between. Embedded with the support layer 40. Moreover, the thickness of the coating part G and the thickness of the support layer 40 are the same. In addition, the thickness of the coating part G is a thickness in a state in which the coating part G immediately after pressing is slightly restored in the thickness direction (so-called spring back), and the thickness does not increase thereafter. It is the thickness in the state. Therefore, the surface of the coating part G whose thickness has been restored and the surface of the support layer 40 are located on the same plane, and are between the coating part G and the support layer 40 adjacent to each other in the longitudinal direction of the positive electrode metal foil 22. There is no step and a continuous surface is formed.

  In the winding process, the positive electrode metal foil 22 provided with the coating part G and the support layer 40 is wound on the winding roll 46 for firing along the longitudinal direction. Winding in a state in which a coating part G wound on the winding roll 46 for firing (hereinafter referred to as a wound coating part G) overlaps with another coating part G wound up thereafter. Taken.

  As shown in FIG. 6, in the firing step, a firing winding roll 46 on which the positive electrode metal foil 22 is wound is set in a firing furnace 48, and the coating part G is heated as it is. Then, the solvent remaining in the coating part G evaporates, the binder is cured, and the positive electrode active material layer 23 is formed from the coating part G.

In the removing step, the support layer 40 adhered to the uncoated part M is peeled off from the positive electrode metal foil 22 to remove the support layer 40 from the positive electrode metal foil 22 and to expose the uncoated part M. .
As shown in FIG. 7, in the punching process, the positive electrode metal foil 22 is pulled out from the firing winding roll 46 and conveyed on the table 50. Then, the positive electrode metal foil 22 on the table 50 is punched out using a mold (not shown), whereby the positive electrode active material layer 23 is formed in a predetermined shape and the uncoated portion M is exposed to the positive electrode side inactive material. The layer portion 22d and the positive electrode current collecting tab 31 are formed, and the positive electrode 21 is manufactured. The negative electrode 24 is also manufactured by the same method as the positive electrode 21.

Next, the effect | action of the manufacturing method of the positive electrode 21 is demonstrated.
In the support layer forming step after the pressing step, the support layer 40 is formed according to the thickness of the coated portion G after pressing, and the coating portion G and the support layer 40 are formed along the longitudinal direction of the positive electrode metal foil 22. A continuous surface was formed. Then, as shown in FIG. 5A and FIG. 6, in the winding process, the positive electrode metal foil 22 is wound around the firing winding roll 46, and the coated coating part G is wound. Another coating part G is piled up. At this time, another coating part G that overlaps the wound coating part G is pushed toward the winding roll 46 for firing due to the weight and winding of the superimposed metal foil 22 for positive electrode.

  Then, another coated part G that protrudes in the longitudinal direction from the wound coated part G tends to fall toward the winding roll 46 for firing. However, the support layer 40 is provided at the tip of the fall. Therefore, another pressed coating portion G is supported by the support layer 40 and is prevented from being bent toward the winding roll 46 for firing.

  And the metal foil 22 for positive electrodes wound by the winding roll 46 for baking by the winding process is provided to a baking process with the winding state. Even during the baking process, the coating part G is supported by the support layer 40 and is prevented from being bent. Therefore, even if the coating part G is cured, the coating part G can be prevented from being wound. Note that, in the manufacturing method of the negative electrode 24, the same action as that of the manufacturing method of the positive electrode 21 can be obtained.

According to the above embodiment, the following effects can be obtained.
(1) After the pressing step, the support layer 40 was formed in accordance with the thickness of the coating part G whose thickness was restored. For this reason, in the winding process, even if another wound coating part G is pushed toward the winding roll 46 for firing, another coating part G that protrudes from the wound coating part G. Is supported by the support layer 40 and is prevented from being bent toward the winding roll 46 for firing. As a result, in the longitudinal direction of the metal foil for positive electrode 22 and the metal foil for negative electrode 25, another coating part G is prevented from being bent from the edge of the wound coating part G, and another coating part It is possible to prevent winding marks from being attached to G. As a result, unevenness can be prevented from being formed in the coating part G, and the flat-surface positive electrode active material layer 23 and negative electrode active material layer 26 can be formed.

  Therefore, in the electrode assembly 14 obtained by laminating the positive electrode 21 and the negative electrode 24, it is possible to suppress variation in the distance between the positive electrode active material layer 23 and the negative electrode active material layer 26 facing each other.

  (2) The support layer 40 is provided over the entire length of the uncoated part M along the longitudinal direction of the positive electrode metal foil 22 and the negative electrode metal foil 25, and the support layer 40 is not applied to the uncoated part M. Are provided throughout. For this reason, no step is formed between the coating part G and the support layer 40 adjacent in the longitudinal direction, and the support layer 40 is formed along the longitudinal direction on the surfaces of the positive electrode metal foil 22 and the negative electrode metal foil 25. And a continuous surface of the coating part G can be formed. Therefore, even if another coating portion G protruding from the wound coating portion G tries to fall down toward the winding roll 46 for firing, the support layer 40 causes one end portion of the other coating portion G to fall. Since up to the other end is supported by the support layer 40, the coating part G can be reliably prevented from being bent.

  (3) Since the thickness of the support layer 40 is the same as the thickness of the restored coating part G, the support layer 40 and the coating part G have the same thickness. For this reason, in the winding process, even if the coating part G wound on the winding roll 46 for firing protrudes from the coating part G that has been wound and falls toward the winding roll 46 for firing, And it can support reliably by the support layer 40, without bending, and it can prevent that a winding trace is attached to another coating part G.

  (4) After the winding process, the coating part G has a firing process. The positive electrode metal foil 22 and the negative electrode metal foil 25 are subjected to the firing step while being wound on the firing roll 46. And in the coating part G, since the other coating part G which protruded from the winding-up coating part G is supported by the support layer 40 in the coating part G, it is baked and hardened. Also, it is possible to prevent the winding part from being applied to the coating part G.

In addition, you may change the said embodiment as follows.
(Circle) the thickness of the support layer 40 may be a little thinner than the thickness of the coating part G which thickness restored, and may be a little thicker.

  ○ The support layer 40 supports the collapsed coating part G, and the size of the support layer 40 may be changed as long as there is no winding trace, and the entire uncoated part M as in the embodiment. It does not have to be provided. For example, the support layer 40 may be provided only in a region corresponding to the length of the uncoated portion M where another coated portion G protrudes from the wound coated portion G.

  The support layer 40 may be provided over the entire length N of the uncoated portion M along the longitudinal direction of the positive electrode metal foil 22 and the negative electrode metal foil 25, but the positive electrode metal foil 22. And in the transversal direction of the metal foil 25 for negative electrodes, it does not need to be provided over the whole. For example, the support layer 40 may be provided over the entire length N of the uncoated portion M at both ends in the short direction and the center of the positive electrode metal foil 22 and the negative electrode metal foil 25. Good.

(Circle) the support layer 40 may be the coating film formed with the coating material which can be removed from the metal foil 22 for positive electrodes, and the metal foil 25 for negative electrodes.
In the embodiment, the coating portion G is formed on both surfaces of the positive electrode metal foil 22 and the negative electrode metal foil 25, and the support layer 40 is formed on both surfaces of the positive electrode metal foil 22 and the negative electrode metal foil 25. When the coating part G is formed on one surface of the metal foil 22 for negative electrode and the metal foil 25 for negative electrode, the support layer 40 may be formed only on the surface on which the coating part G is formed.

The press process may be performed by a press machine having a flat press surface instead of the press rollers 63a and 63b.
○ The cutting process may be performed simultaneously with the punching process.

O The power storage device may be embodied in another power storage device such as an electric double layer capacitor.
The secondary battery 10 may be a lithium ion secondary battery or another secondary battery. In short, any ion may be used as long as ions move between the positive electrode active material layer and the negative electrode active material layer and transfer charge.

Next, the technical idea that can be grasped from the above embodiment and other examples will be described below.
(A) one electrode having an active material layer on at least one surface of a metal foil, the other electrode having an active material layer having a polarity different from the one electrode, and a separator, and the one electrode A power storage device having an electrode assembly stacked with the other electrode interposed between separators, wherein the electrode is manufactured by the manufacturing method according to any one of claims 1 to 4. A power storage device which is characterized by being made.

  (B) The power storage device according to the technical concept (a), in which the power storage device is a secondary battery.

  G ... coated part, M ... uncoated part, N ... length, 21 ... positive electrode as electrode, 22 ... metal foil for positive electrode as metal foil, 23 ... active material layer for positive electrode as active material layer, 24 ... Negative electrode as electrode, 25 ... Metal foil for negative electrode as metal foil, 26 ... Active material layer for negative electrode as active material layer, 40 ... Support layer, 46 ... Winding roll for firing as winding roll.

Claims (4)

An electrode manufacturing method comprising an active material layer on at least one side of a metal foil,
An active material mixture containing an active material is applied to at least one surface of a strip-shaped metal foil at intervals along the longitudinal direction of the metal foil to form a coating portion, and adjacent to the longitudinal direction. An application process for forming an uncoated part where the active material mixture is not applied between the coated parts,
A pressing step of pressing the coating part;
A support layer forming step, which is performed after the pressing step, and is provided on the uncoated portion with a support layer made of a material different from the coated portion;
A winding step of winding the band-shaped metal foil after the support layer forming step on a winding roll along the longitudinal direction.   The thickness of the said support layer is the same as the thickness of the said coating part after the said press process, The manufacturing method of the electrode of Claim 1.   The said support layer is a manufacturing method of the electrode of Claim 1 or Claim 2 provided over the whole length of the said uncoated part along the longitudinal direction of the said metal foil.   The manufacturing method of the electrode as described in any one of Claims 1-3 which has the baking process of the said coating part after the said winding-up process.