JP6413254B2 - Method for manufacturing electrode for secondary battery - Google Patents

Description

  The present invention relates to a method for producing an electrode used as a positive electrode or a negative electrode of a secondary battery represented by a lithium ion secondary battery.

  For example, as a thin lithium ion secondary battery using a laminate film outer package, an electrode laminate in which a plurality of sets of positive electrodes and negative electrodes are laminated together with a separator is stored inside the laminate film outer package. Both of the positive electrode and the negative electrode are current collectors made of aluminum or other metal foil, and the current collector is not applied to the active material (current collector exposed portion) to be a lead portion. A positive electrode active material layer is formed by applying a positive electrode active material thereon, and a negative electrode active material layer is formed by applying a negative electrode active material on a current collector for the negative electrode.

  In this case, although it is not a thin secondary battery using a laminate film outer package, for example, in Patent Document 1, an active material uncoated portion (current collector exposed portion) and an active material layer of an electrode for a secondary battery are disclosed. A technique is described in which an insulating tape for the purpose of preventing a short circuit is applied across the board.

JP 2006-0119199 A

  However, in the conventional technique represented by Patent Document 1, a heat-welding tape is used as the insulating tape, and the heat is applied by a so-called hot press method with the insulating tape disposed at a predetermined position of the electrode. Since the active material is not applied to the active material uncoated part (current collector exposed part) and the active material layer, the active material uncoated part (current collector exposed part) and the active material layer are both bonded. It was difficult to reliably apply with uniform adhesive strength.

  In particular, the active material uncoated part may damage the current collector or insulating tape due to overheating, for example, so-called "thermal wrinkles" occur on the insulating tape after application, which causes the quality of the tape application part. The decline is feared.

  The present invention has been made paying attention to such a problem, and for an insulating tape that is attached to a boundary portion between an active material application region and an active material non-application region of an electrode, The present invention provides a method for producing an electrode for a secondary battery that can be applied with a uniform adhesive strength regardless of whether it is a coated region or an active material uncoated region.

  In the present invention, an active material application region in which an active material is applied to a surface of a current collector and an active material non-application region in which no active material is applied are formed. It is a manufacturing method of the electrode for secondary batteries by which the boundary part with an area | region is coat | covered with the insulating tape which straddles both.

  Then, a heat-welding insulating tape is disposed across the boundary between the active material application area and the active material non-application area on the surface of the current collector, and the insulating tape is heated to the current collector. The insulating tape is attached to the current collector by heat welding.

In addition, the heating die includes a first impulse heater provided corresponding to the active material application region in the surface layer portion of the die body, and a second impulse provided corresponding to the active material non-application region. comprise a heater, a, the first, second impulse heater has a current-controlled heater that generates heat by being supplied with current individually. Then, the current supplied to the second impulse heater is made smaller than the current supplied to the first impulse heater, so that the temperature of the portion corresponding to the active material non-application region in the heating type is applied to the active material. The temperature is lower than the temperature of the portion corresponding to the region.

  According to the present invention, the insulating tape is applied so as to straddle both the active material application region and the active material non-application region, but has a large heat capacity due to the application of the active material. In the active material application area, the heat temperature applied by the heating mold is relatively high. Conversely, since the active material is not applied, the heat temperature applied by the heating mold is relatively low in the active material uncoated area where the heat capacity is small. Therefore, it is possible to reliably apply an insulating tape with uniform adhesive strength regardless of whether it is an active material application region or an active material non-application region. And damage to the insulating tape due to overheating can be avoided.

The figure which shows 1st Embodiment of the manufacturing method of the electrode which concerns on this invention, and is schematic explanatory drawing of an insulating tape sticking process. Cross-sectional explanatory drawing along the longitudinal direction of FIG. Plane explanatory drawing of the electrode cut out from the electrode sheet of FIGS. FIG. 5 is a view showing a second embodiment of the electrode manufacturing method according to the present invention, and is a cross-sectional explanatory view of the same portion as FIG. 2. FIG. 9 is a diagram showing a third embodiment of an electrode manufacturing method according to the present invention, and is a cross-sectional explanatory view of the same portion as FIG. 2.

  1 and 2 show a more specific first embodiment for carrying out the method for manufacturing an electrode for a secondary battery according to the present invention. FIG. FIG. 1 shows a cross-sectional view along the longitudinal direction of FIG.

  As shown in FIGS. 1 and 2, the electrode sheet 1 is formed by intermittently fixing active material layers 3 a and 3 b along the longitudinal direction on both front and back surfaces of a long foil-like current collector 2. Then, the sheet is sequentially supplied to the attaching step S from the arrow direction a so as to be fed out from a winding roll (not shown). In the example of FIGS. 1 and 2, the active material layers 3 a and 3 b are intermittently formed on the front and back surfaces of the current collector 2 that is the base of the electrode 1, so that the active material layer as an active material application region in the longitudinal direction. 3a, 3b and the active material non-application area | region 4 in which the active material is not apply | coated are located alternately. Note that the active material non-applied region 4 can be regarded as a current collector exposed portion where the base current collector 2 is exposed to the outside as it is because no active material is applied.

  1 and 2, on the surface side of the electrode sheet 1, the boundary between the active material layer 3 a and the active material uncoated region 4 adjacent to the active material layer 3 a is covered with the insulating tape 5 across the both. In order to do so, an object is to stick the insulating tape 5 having a predetermined width having heat welding property with a predetermined adhesive strength by heat welding. Therefore, when the electrode sheet 1 is positioned at a predetermined position as will be described later, an insulating tape having a predetermined width is formed at the boundary between the active material layer 3a and the active material uncoated region 4 adjacent thereto. 5 is arranged over the entire width of the electrode sheet 1.

  Here, hereinafter, the longitudinal direction of the electrode sheet 1 (the direction along the direction of arrow a in FIGS. 1 and 2) is defined as the longitudinal direction of the electrode sheet, and the direction orthogonal to the longitudinal direction is defined as the electrode width direction.

  The electrode sheet 1 should also be referred to as a wide and long electrode base material before being cut into individual electrodes 1A as shown in FIG. After passing through the above, the active material layer 3a on the surface side, the insulating tape 5 and the active material non-applied region 4 are arranged in series and cut into one electrode of a predetermined size. The electrode 1A as shown in FIG. 3 is finished through the cutting process. In this case, the active material uncoated region 4 that is also the current collector exposed portion is a so-called tab or lead portion and another terminal (not shown) (current collector of another electrode sheet or electrode terminal led out of the battery). It will function as a connection part.

  1 and 2, an upper heating die 6 and a lower heating die 7 having the same width as the insulating tape 5 are disposed opposite to each other across the electrode sheet 1 in the vertical direction. Both heating dies 6 and 7 have two sets of impulse heaters 8 and 9 as heaters that are heating elements on the surface layer side facing the electrode sheet 1 of the die bodies 6 a and 7 a, that is, the first impulse heater 8. And the second impulse heater 9 are arranged side by side. These two sets of impulse heaters 8 and 9 are set so as to cover the entire width of the insulating tape 5 with the entire width.

  At the same time, the first impulse heater 8 of the two sets of impulse heaters 8 and 9 corresponds to the active material layers 3a and 3b of the electrode sheet 1, and the other second impulse heater 9 is activated. This corresponds to the active material uncoated region 4 adjacent to the material layers 3a and 3b. The heat generation temperature of the second impulse heater 9 is set in advance so as to be lower than the heat generation temperature of the first impulse heater 8.

  This is based on the premise that the insulating tape 5 having a uniform thickness with heat-welding property is applied so as to straddle both the active material layer 3a of the electrode sheet 1 and the active material uncoated region 4 adjacent thereto. The active material layer 3a has a characteristic that the heat capacity is large by the thickness of the active material layer 3a and heat is easily escaped to the current collector 2 side, which is the base material, while the active material is not applied in the active material uncoated region 4. Since the current collector 2 itself is exposed, the heat capacity is small, and this is based on the characteristic that heat does not easily escape to the current collector 2 side.

  Here, the first and second impulse heaters 8 and 9 are ribbon-shaped, and at the same time, generate a heat by flowing a low voltage and high current instantaneously. There is an advantage that the temperature can be increased up to. The first and second impulse heaters 8 and 9 can arbitrarily adjust the heat generation temperature by controlling the energization voltage and current independently of each other. In the example of the first and second impulse heaters 8 and 9, the energization current to the second impulse heater 9 is set in advance smaller than that of the first impulse heater 8.

  1 and 2, the thickness dimensions of the first and second impulse heaters 8 and 9 are exaggerated in addition to the thickness dimensions of the active material layers 3a and 3b and the insulating tape 5.

  Accordingly, in the attaching step S shown in FIGS. 1 and 2, the electrode sheets 1 positioned between the two heating dies 6 and 7 are separated from each other by a predetermined amount in the direction of the arrow a. When the electrode sheet 1 is fed by one pitch intermittently, the active material coating layers 3a and 3b and the active material uncoated region adjacent to the heating dies 6 and 7 are disposed between the heating dies 6 and 7 because the electrode sheet 1 is fed by pitch. 4 is positioned. Then, after this positioning, the insulating tape 5 is stretched over the entire width of the electrode sheet 1 so as to straddle the boundary between the active material layer 3a on the surface side and the active material uncoated region 4 by a tape supply means (not shown). Is supplied. As the heat-welding insulating tape, for example, polypropylene is used.

  Subsequent to the supply of the insulating tape 5, the two heating dies 6, 7 move closer to each other and the heating dies 6, 7 pressurize and restrain the insulating tape 5 together with the electrode sheet 1. The second impulse heaters 8 and 9 are energized, and the first and second impulse heaters 8 and 9 instantaneously generate heat. Thereby, the insulating tape 5 superposed on the boundary portion between the active material layer 3a and the active material uncoated region 4 in addition to the vicinity of the boundary between the active material layer 3a and the active material layer 3a As a result, the insulating tape 5 is adhered to the boundary portion between the active material layer 3a on the surface side and the active material uncoated region 4 by adhesive bonding by so-called thermal welding.

  In this case, the heat capacity is large on the active material layers 3a and 3b side, and heat easily escapes to the current collector 2 side which is the parent body, while the heat capacity is small on the active material uncoated region 4 side, and the current collector which is the mother body. Since the heat does not easily escape on the second side, the heat generation temperature of the second impulse heater 9 is set in advance so as to be lower than the heat generation temperature of the first impulse heater 8 in consideration of these points. It is as described above.

  Therefore, the current collector 2 and the insulating tape 5 are not damaged due to overheating on the active material uncoated region 4 side, so that generation of “thermal wrinkles” can be prevented and the active material layer 3a. In addition, the insulating tape 5 can be reliably and uniformly attached with uniform adhesive strength in both the active material uncoated region 4 adjacent thereto. As a result, the affixing quality of the insulating tape 5 is uniform and stable.

  Here, the heat generation temperature of the first impulse heater 8 on the lower heating mold 7 side is set lower than the heat generation temperature of the first impulse heater 8 on the upper heating mold 6 side, and the first heating heater on the upper heating mold 6 side is similarly set. The heat generation temperature of the second impulse heater 9 on the lower heating mold 7 side is set lower than the heat generation temperature of the second impulse heater 9, and the lower heating mold 7 is pushed against the electrode sheet 1 prior to the upper heating mold 6. It is possible to make the lower heating mold 7 function substantially as a preheating mold.

  FIG. 4 is a diagram showing a more specific second embodiment for carrying out the method for manufacturing an electrode for a secondary battery according to the present invention, in a portion common to FIG. 2 which is the previous first embodiment. Are given the same reference numerals.

  In the second embodiment, the thermal conductivity of both the upper heating mold 6 and the lower heating mold 7 is higher than that of the mold bodies 6a and 7a between the mold bodies 6a and 7a and the second impulse heater 9. A heat insulating material 10 is interposed as a small low thermal conductivity member.

  According to the second embodiment, the mold bodies 6a and 7a and the second impulse heater 9 in both the heating molds 6 and 7 are thermally disconnected due to the presence of the heat insulating material 10, so that the second The heat generation temperature of the first impulse heater 9 is not easily affected by the heat generation temperature of the first impulse heater 8, and the heat generation temperature of the first impulse heater 8 and the heat generation temperature of the second impulse heater 9 are individually and more precisely controlled. It becomes possible to do. As a result, the attaching quality of the insulating tape 5 including the uniform bonding strength of the insulating tape 5 in the active material layer 3a and the active material uncoated region 4 is further improved.

  FIG. 5 is a diagram showing a more specific third embodiment for carrying out the method for manufacturing an electrode for a secondary battery according to the present invention, and is in a portion common to FIG. 4 which is the previous second embodiment. Are given the same reference numerals.

  This third embodiment is an example in the case where the insulating tape 5 is applied to the back surface side as well as the front surface side of the electrode sheet 1, and the electrode sheet 1 is placed so as to face the insulating tape 5 on the front surface side. The insulating tape 15 is also arranged on the back side of the gap. Then, if both heating dies 6 and 7 are moved closer to each other and the insulating tapes 5 and 15 on both the front and back sides are pressed and restrained together with the electrode sheet 1, the active material layers 3a and 3b and Insulating tapes 5 and 15 are bonded to the boundary portion with the active material uncoated region 4 by thermal welding so as to straddle both of them.

  And since the two insulating tapes 5 and 15 are affixed simultaneously in the front and back both surfaces side of the electrode sheet 1, the insulating tape 5 is provided only on the surface side of the electrode sheet 1 as in the first and second embodiments. As compared with the case of pasting, the necessary thermal conditions are different. In response to the requirement of such different thermal conditions, in both the upper heating mold 6 and the lower heating mold 7, the heating temperatures of the first and second impulse heaters 8 and 9 are individually adjusted. The energization current to the first and second impulse heaters 8 and 9 is controlled.

  Therefore, according to the third embodiment, the two insulating tapes 5 and 15 can be applied at the same time with the same attachment quality as when one insulating tape 5 is attached, thereby shortening the process. In addition, the number of heating dies and power consumption can be reduced.

DESCRIPTION OF SYMBOLS 1 ... Electrode sheet 1A ... Electrode 2 ... Current collector 3a, 3b ... Active material layer (active material application area | region)
4 ... Active material uncoated region 5 ... Insulating tape 6 ... Upper heating mold 6a ... Mold body 7 ... Lower heating mold 7a ... Mold body 8 ... First impulse heater (first heating element)
9: Second impulse heater (second heating element)
10 ... Insulating material (low thermal conductivity member)
15 ... Insulating tape S ... Paste process

Claims (4)

An active material application region where an active material is applied to the surface of the current collector and an active material non-application region where no active material is applied are formed, and the boundary between the active material application region and the active material non-application region A method for producing an electrode for a secondary battery in which a part is covered with an insulating tape straddling both,
Place a heat-welding insulating tape across the boundary between the active material application area and the active material non-application area on the surface of the current collector,
By pressing the insulating tape against the current collector with a heating die, the insulating tape is attached to the current collector by heat welding,
The heating mold includes a first impulse heater provided corresponding to the active material application region in a surface layer portion of the die body, and a second impulse heater provided corresponding to the active material non-application region. equipped,
The first and second impulse heaters are current-controlled heaters that generate heat when individually supplied with current,
By making the current supplied to the second impulse heater smaller than the current supplied to the first impulse heater, the temperature of the portion corresponding to the active material uncoated region in the heating type is changed to the active material coated region. The manufacturing method of the electrode for secondary batteries characterized by making it lower than the temperature of a corresponding part. 2. The secondary battery according to claim 1, wherein a low thermal conductivity member having a smaller thermal conductivity than that of the mold body is provided between the heating mold body and the second impulse heater . Electrode manufacturing method. The insulating tape is attached by thermal welding by press-clamping the insulating tape together with the current collector between the upper heating mold and the lower heating mold disposed opposite to each other,
The upper heating mold and the lower heating mold include a first impulse heater provided corresponding to the active material application area in the surface layer portion of the mold main body and a second impulse heater provided corresponding to the active material non-application area. An impulse heater ,
The first and second impulse heaters are current-controlled heaters that generate heat when individually supplied with current,
The current supplied to the second impulse heater is made smaller than the current supplied to the first impulse heater, so that the temperature of the portion corresponding to the active material non-application region of both heating types is applied to the active material. The method for manufacturing an electrode for a secondary battery according to claim 1 or 2, wherein the temperature is lower than a temperature of a portion corresponding to the region . An active material application region where an active material is applied to both the front and back surfaces of the current collector and an active material uncoated region where no active material is applied are formed respectively.
A heat-welding insulating tape is arranged on each of the boundary portions between the active material application region and the active material non-application region on both sides of the current collector,
Claim, characterized in that pasting the insulating tape by hot welding on both sides of the current collector by pressing the front and rear surfaces of the insulating tape at top heating type and a lower heated mold to the collector 3 The manufacturing method of the electrode for secondary batteries as described in 2 ..

Images