JP2949153B2 - Method for producing current collector for electrochemical cell - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing a current collector for an electrochemical cell using a carbon current collector as a current collector in contact with an electrode of the electrochemical cell. .

[Prior Art] Conventionally, as a current collector of a fuel cell, a carbon current collector made of a carbonaceous material such as graphite has been widely used. In a conventional carbon current collector, a connector for extracting electric power to the outside was also formed of a carbonaceous material integrally with the current collector. However, if the connector is formed from a carbonaceous material, the current collector resistance increases, so a metal current collector made of copper, iron, nickel, etc. with a connector is fixed on the side of the carbon current collector that does not contact the electrode. A current collector for an electrochemical cell has been proposed. In this type of cell current collector, a metal current collector is fixed to a carbon current collector using a foamable adhesive sheet containing a polyethylene resin or the like as a main component, which foams when heated to a predetermined temperature and exhibits elasticity. ing.

6A and 6B respectively show a part of the steps of a conventional method for manufacturing a current collector. Conventionally, as shown in FIG. 6A, a metal current collector having a smaller outer dimension and a connector than the carbon current collector 1 is provided on the surface of the carbon current collector 1 opposite to the surface in contact with the electrode. The metal current collector 2
Is placed outside the metal current collector 2 with an insulating foamable adhesive sheet 3 larger than the outer dimensions of the metal current collector 2. Next, in order to limit foaming in the thickness direction of the foamable adhesive sheet 3, these are disposed between the fixture main body 4 having a U-shaped cross section and the plate-shaped fixing plate 5, and the nut 6 is tightened. Foaming adhesive sheet 3
Pressure. Release agents 7 and 8 are applied to the surface of the fixture main body 4 that contacts the carbon current collector plate 1 and the surface of the fixing plate 5 that contacts the foamable adhesive sheet 3, respectively. As shown in FIG. 6A, while the carbon current collector 1, the metal current collector 2 and the foamable adhesive sheet 3 are restrained, the entire body is heated to the foaming temperature of the foamable adhesive sheet 3 to thereby provide elasticity. Is formed. Foamable adhesive sheet 3
Since the expansion in the laminating direction is limited by the fixing plate 5, it expands in the lateral direction orthogonal to the laminating direction. This foamed adhesive sheet shows an adhesive force during foaming and adheres to the contact surface between the metal current collector 2 and the carbon current collector 1. Therefore, when the foaming is completed, an adhesive portion X is formed between the carbon current collector 1 and the heat-foamed adhesive layer 9 so as to mainly surround the outer periphery of the metal current collector 2. The metal current collector 2 is fixed to the carbon current collector 1 by the adhesive force of the bonding portion X.

The elasticity of the heat-foamable adhesive layer 9 generates an urging force for pressing the carbon current collector 1 against the electrode when the cell current collector is arranged in the case and compressed in the stacking direction. Further, the metal foam 2 is coated with the heat-foaming adhesive layer 9 so as not to be exposed, thereby preventing corrosion of the metal current collector 2 by the electrolytic solution.

[Problems to be Solved by the Invention] However, when the currently known foamed adhesive sheet 3 is pressurized at the time of foaming by the fixture main body 4 and the fixing plate 5, the bonding property of the foamed adhesive sheet 3 itself becomes strong, and this bonding is performed. When the property becomes stronger, the elasticity of the heat-foamed adhesive layer 9 after foaming becomes lower. If the foamable adhesive sheet 3 is heated without applying any pressure at the time of foaming, the adhesive force between the heat-foamable adhesive layer 9 and the carbon current collector 1 and the metal current collector 2 becomes weak, and the carbon current collector 1 The contact resistance between the metal and the metal current collector 2 increases. As described above, since the adhesive strength and the elasticity are in inverse proportion, it is difficult to obtain appropriate adhesive strength and elasticity only by the heat-foamable adhesive layer 9 as in the conventional current collector for a cell. It has been difficult to sufficiently increase the contact pressure between the carbon current collector 1 and the electrode and between the metal current collector 2 and the carbon current collector 1 to lower the contact resistance therebetween.

An object of the present invention is to provide a method for producing a current collector for an electrochemical cell, which has a large elasticity and an improved current collection performance without lowering the adhesive strength of a heat-foamable adhesive layer.

[Means for Solving the Problems] In the production method of the present invention, a step of arranging a metal current collector in contact with one side surface of a carbon current collector, and a step of foaming when heated to provide elasticity and adhesion A first foamable adhesive sheet exhibiting a property is placed on a non-contact surface of the metal current collector in a state of being pressed in a laminating direction and heated, thereby forming a part of the metal current collector and the carbon current collector. Forming a heat-foamable adhesive layer for fixing the metal current collector to the carbon current collector by coating the heat-foamable adhesive layer; Forming a high elasticity layer having higher elasticity than the heat-foamable adhesive layer by arranging and heating a conductive adhesive sheet to produce a current collector for an electrochemical cell.

Then, in the step of forming the high elasticity layer, the second foamable adhesive sheet is heated without pressure.

It is preferable that the foaming temperature of the first foamable adhesive sheet is higher than the foaming temperature of the second foamable adhesive sheet.

It goes without saying that the high elasticity layer may be composed of not only one layer but also a plurality of layers.

In the step of forming the heat-foamable adhesive layer, a third foamable adhesive sheet having a higher foaming temperature and a lower foaming ratio than the first foamable adhesive sheet is arranged near the outer peripheral portion of the metal current collector. Heat foaming is performed, and then the first foamable adhesive sheet is heated.

[Operation] In the method of the present invention, the first foamable adhesive sheet is foamed in a pressurized state, so that a sufficient adhesive force can be imparted to the heat-foamable adhesive layer. Since the high elasticity layer is formed using the second foamable adhesive sheet in the same manner as the heat-foamable adhesive layer, the heat-foamable adhesive layer and the high-elasticity layer can be sufficiently joined together with the formation of the high elasticity layer. it can. In particular, in the present invention,
In the step of forming the high elasticity layer, the second foamable adhesive sheet is heated in a non-pressurized state, so that sufficient elasticity can be obtained.

Further, when the foaming temperature of the first foamable adhesive sheet is higher than the foaming temperature of the second foamable adhesive sheet, the heated foamed adhesive layer does not re-foam when the second foamed adhesive sheet is heated. A decrease in force can be prevented.

In the step of forming the heat-foamable adhesive layer, a third foamable adhesive sheet having a higher foaming temperature and a lower foaming ratio than the first foamable adhesive sheet is arranged near the outer peripheral portion of the metal current collector. By performing heating foaming and then heating the first foamable adhesive sheet, it is possible to increase the adhesive force and to prevent the heated foaming adhesive layer from expanding more than necessary in the lateral direction. And post-processing becomes easier.

Embodiment An embodiment of the present invention will be described below with reference to the drawings. First
FIGS. A and B are cross-sectional views of the electrochemical cell using the cell current collector 10 of the present invention during the assembly and after the assembly is completed, respectively. In these figures, 11 is a carbon current collector, 12 is a metal current collector, 13 is a heat-foamed adhesive layer, and 14 is a high elasticity layer. Reference numeral 15 denotes an electrolyte, and reference numerals 16 and 17 denote a negative electrode and a positive electrode. A pair of cell current collectors 10 is arranged so as to sandwich the negative electrode 16 and the positive electrode 17 arranged on both sides of the electrolyte 15, and the combination type battery frames 18 and 19 are combined to complete an electrochemical cell.

The battery frames 18 and 19 are provided with contact portions 18a and 19a, respectively, which contact the high elastic layer 14 of the cell current collector 10 and press the high elastic layer 14, and the contact portions 18a and 19a Passage 20 (abutment portion) that constitutes a part of a circulation passage for circulating fuel
18 are not shown). The passage 20 has a U-shaped cross section and is formed of a groove that opens to the cell current collector side and extends in the vertical direction. The passage 20 communicates with the upper passage 21 and the lower passage 22.

As shown in FIGS. 2A and 2B, the carbon current collector 11 and the metal current collector 12 of the cell current collector 10 each have three holes 11a.
And 12a are formed. The metal current collector 12 has a smaller outer dimension than the carbon current collector 11, and the hole 12a of the metal current collector 12 is formed to have a larger diameter than the hole 11a of the carbon current collector 11. A portion extending from the metal current collector 12 through the battery frames 18 and 19 serves as a terminal for outputting electric power to the outside.
b.

The heat-foamable adhesive layer 13 is formed by heat-foaming a foamable adhesive sheet containing, for example, a polyethylene resin as a main component. The heat foamed adhesive layer 13 is also formed with three holes 13a having substantially the same diameter as the holes 11a of the carbon current collector 11. The high elasticity layer 14 also has three holes 14a having substantially the same diameter as the holes 11a of the carbon current collector 11.
Individually formed. Fuel chambers 23 are formed from these holes 11a, 13a and 14a. One end of the fuel chamber 23 opens toward the negative electrode 16 or the positive electrode 17, and the other end communicates with the passage 20. Therefore, fuel supplied from a fuel supply port (not shown) is supplied to each fuel chamber 23 through the passage 20.

When manufacturing the current collector 10 for a cell, specifically, for example, a jig 24 as shown in FIG. 3A is used. This jig
24 has a pair of fixing plates 25 and 26, and bolts 27 are penetrated at the four corners of these fixing plates 25 and 26, and at least the fixing plate 26 moves in the axial direction of the bolt 27. It is configured to be possible. A coil spring 29 is disposed between the nut 28 screwed to the tip of the bolt 27 and the fixing plate 26, and the fixing plate 26 can be biased toward the fixing plate 25 by tightening the nut 28.

Three rod members 30 are fixed to the fixing plate 25. The fixing plate 26 has a through hole 26a through which the rod member 30 movably passes. Fixing plates 25 and 26
A release agent 31 such as an oily fluororesin is applied to the opposite side surfaces of the mold. It is preferable that the surface of the rod member 30 is also coated with a release agent.

When forming the heat-foamable adhesive layer 13, the carbon current collector 11
, A metal current collector 12 and a perforated foamable adhesive sheet 13 ′ are laminated, and the rod member 30 is connected to the hole 11 a of the carbon current collector 11, the hole 12 a of the metal current collector 12, and the hole of the foamable adhesive sheet 13 ′. Through
The nut 28 is tightened, and the laminate is sandwiched between the fixed plate 25 and the fixed plate 26 while being pressed at a predetermined pressure.

Thereafter, the jig 24 is inserted into a heating furnace heated to the foaming temperature of the first foamable adhesive sheet 13 'to foam the foamable adhesive sheet 13'. Part of the foamed sheet 13 ′ enters between the rod member 30 and the hole 12 a of the metal current collector 12 and covers the exposed surface of the metal current collector 12 and the exposed surface of the carbon current collector 11. FIG. 3B shows a state in which the rod member 30 is omitted and the foam is cooled to room temperature after completion of foaming. During foaming, the fixed plate 26 is released by the biasing force of the coil spring 29.
Moves toward the fixing plate 25, and the pressurized state is maintained.
Therefore, the bonding property of the heat-foamable adhesive layer 13 is increased, and the adhesive strength of the bonding portion X between the heat-foamable adhesive layer 13 and the carbon current collector 11 is significantly increased as compared with the conventional case.

Next, the nut 28 is loosened, the fixed plate 26 is removed, and the fixed plate 25 is placed on the base with the fixed plate 25 facing down. Then, as shown in FIG. 4A, a second foamable adhesive sheet 14 ′ is arranged without pressure in order to form a high elasticity layer 14 on the heat-foamable adhesive layer 13. In FIG. 4, the rod member 30 is omitted as in FIG. 3B. For this reason, the second foamable adhesive sheet 14 ′ is shown without a hole formed therein, but the second foamable adhesive sheet 14 ′ actually has a hole into which the rod member 30 is inserted. ing. The second foamable adhesive sheet 14 'has a lower foaming temperature and a higher foaming ratio than the first foamable adhesive sheet 13'. Therefore, even when the second foamable adhesive sheet 14 'is foamed, the heat-foamable adhesive layer 13 is not thermally affected at all, and the adhesive strength does not decrease.

FIG. 4B shows a state in which the second foamable adhesive sheet 14 ′ is heated at a predetermined temperature and foamed to form the high elasticity layer 14. Since the high elasticity layer 14 is formed in a non-pressurized state, it has excellent elasticity. The high elasticity layer 14 is firmly bonded to the heat-foamable adhesive layer 13 during foaming. In the present embodiment, especially when foaming each foamable adhesive sheet, since foaming in the horizontal direction is not restricted, as shown in FIG. 4B, the heat foaming adhesive layer 13 and the high elasticity layer 14 are It bulges out in the lateral direction. Therefore, in this embodiment, unnecessary portions are cut off by using an appropriate cutting means such as a cutter to adjust the shape, and the shape is shaped as shown in FIG. 4C.

When an experiment was conducted on a fuel cell configuration in which the cell current collector manufactured as described above was assembled in the mode shown in FIG. 1B, the resistance value between the electrode and the metal current collector was higher than in the prior art. It was confirmed that it could be reduced by nearly 30%.
As an example, the resistance value when using this embodiment is 48 mΩ.
Met. In the conventional device, even a small one has a resistance value of about 80 mΩ.

In the above embodiment, the high elasticity layer is formed using a foamed adhesive sheet, but the high elasticity layer can be replaced with another known elastic body such as rubber as long as it has elasticity equal to or higher than a predetermined value. it can. When another elastic body is used, the elastic body may be joined to the heat-foamable adhesive layer using an appropriate adhesive.

In the above embodiment, the thickness of the metal current collector 12 has a certain limit in increasing the adhesive strength between the heat-foamable adhesive layer and the carbon current collector. Therefore, before forming the heat-foaming adhesive layer 13, as shown in FIG.
The third foaming adhesive sheet 13 ″ having a higher foaming temperature and a lower foaming ratio than the foaming adhesive sheet 13 ′ of FIG. In this case, three heating foaming operations are performed.

In the above embodiment, the high elasticity layer has a single-layer structure, but may have a two or more-layer structure if necessary. FIG. 5B shows a cross-sectional view of another embodiment having a reinforcing adhesive layer 30 and a high elasticity layer having a two-layer structure.

[Effects of the Invention] As described above, in the method of the present invention, since the first foamable adhesive sheet is foamed in a pressurized state, a sufficient adhesive force can be imparted to the heat-foamable adhesive layer. Since the high elasticity layer is formed using the second foamable adhesive sheet in the same manner as the heat-foamable adhesive layer, the heat-foamable adhesive layer and the high elasticity layer can be sufficiently joined together with the formation of the high elasticity layer. it can.
In particular, in the present invention, in the step of forming the high elasticity layer, the second foamable adhesive sheet is heated in a non-pressurized state, so that sufficient elasticity can be obtained.

[Brief description of the drawings]

FIGS. 1A and 1B are a cross-sectional view before and after assembly of an electrochemical cell provided with an embodiment of the current collector for an electrochemical cell according to the present invention, and FIGS. FIG. 3 is a plan view of a carbon current collector and a metal current collector used in the cell current collector shown in FIG. 1, and FIG. 3A is a cross-sectional view showing a state in which a heat-foamable adhesive layer is formed; FIG. 3B is a cross-sectional view showing a state in which foaming has been completed and a heat-foaming adhesive layer has been formed, and FIGS. 4A to 4C are cross-sectional views showing steps in the case of forming a high elasticity layer. FIGS. 5A and 5B are cross-sectional views used to explain another embodiment of the current collector for a cell of the present invention. FIGS. 6A and 6B are views for manufacturing a conventional current collector for a cell. FIG. 3 is a diagram showing a state before heating and a state after heating, respectively. 10 …… Current collector for electrochemical cell, 11 …… Carbon current collector, 12…
... a metal current collector, 13 ... a heat-foamable adhesive layer, 13 '... a first foamable adhesive sheet, 13 "... a third foamable adhesive sheet,
14 ... High elasticity layer, 14 '... Second foamable adhesive sheet.

──────────────────────────────────────────────────続 き Continued on the front page (58) Fields surveyed (Int.Cl. ⁶ , DB name) H01M 8/02 H01M 8/24 H01M 4/66

Claims (4)

(57) [Claims] 1. A step of arranging a metal current collector in contact with one side surface of a carbon current collector; and forming a first foamable adhesive sheet which expands when heated to show elasticity. By arranging and heating the non-contact surface of the current collector in the laminating direction in a state of being pressed, the metal current collector and a part of the carbon current collector are coated to cover the metal current collector with the carbon current collector. Forming a heat-foamable adhesive layer to be fixed to the current collector; and arranging, on the outer side in the laminating direction of the heat-foamable adhesive layer, a second foamable adhesive sheet that expands when heated and exhibits elasticity. Forming a high elasticity layer having higher elasticity than the heat-foamable adhesive layer. In the step of forming the high elasticity layer, the second foamable adhesive sheet is heated in a non-pressurized state. A method for producing a current collector for an electrochemical cell, comprising: 2. A step of arranging a metal current collector in contact with one side surface of a carbon current collector; and forming a first foamable adhesive sheet which expands when heated to show elasticity. By arranging and heating the non-contact surface of the current collector in the laminating direction in a state of being pressed, the metal current collector and a part of the carbon current collector are coated to cover the metal current collector with the carbon current collector. Forming a heat-foamable adhesive layer to be fixed to the current collector; and arranging, on the outer side in the laminating direction of the heat-foamable adhesive layer, a second foamable adhesive sheet that expands when heated and exhibits elasticity. Forming a high elasticity layer having higher elasticity than the heat-foamable adhesive layer, whereby the foaming temperature of the first foamable adhesive sheet is higher than the foaming temperature of the second foamable adhesive sheet. A method for producing a current collector for an electrochemical cell. 3. A step of arranging a metal current collector in contact with one side surface of a carbon current collector, and forming a first foamable adhesive sheet which expands when heated and exhibits elasticity. By arranging and heating the non-contact surface of the current collector in the laminating direction in a state of being pressed, the metal current collector and a part of the carbon current collector are coated to cover the metal current collector with the carbon current collector. Forming a heat-foamable adhesive layer to be fixed to the current collector; and arranging, on the outer side in the laminating direction of the heat-foamable adhesive layer, a second foamable adhesive sheet that expands when heated and exhibits elasticity. Forming a high elasticity layer having a higher elasticity than the heat-foamable adhesive layer, wherein at least one high elasticity layer is further formed using a foamable adhesive sheet outside the high elasticity layer. Of a current collector for an electrochemical cell. 4. A step of arranging a metal current collector in contact with one side surface of a carbon current collector; and forming a first foamable adhesive sheet which expands when heated to show elasticity. By arranging and heating the non-contact surface of the current collector in the laminating direction in a state of being pressed, the metal current collector and a part of the carbon current collector are coated to cover the metal current collector with the carbon current collector. Forming a heat-foamable adhesive layer to be fixed to the current collector; and arranging, on the outer side in the laminating direction of the heat-foamable adhesive layer, a second foamable adhesive sheet that expands when heated and exhibits elasticity. Forming a high-elasticity layer having higher elasticity than the heat-foamable adhesive layer. In the step of forming the heat-foamable adhesive layer, the first foaming is performed near the outer peripheral portion of the metal current collector. Third foamable contact having a higher foaming temperature and a lower foaming ratio than the foamable adhesive sheet Performing heat foamed by placing the sheet, a manufacturing method of thereafter the first foamable adhesive sheet for electrochemical cell current collector, characterized in that for heating the.