JPH10125332A - Manufacture of battery electrode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a proper electrical connection and improve the productivity of an electrode by applying the constitution that a sheet type three-dimensional porous body is pasted to the surface of a conductive sheet metal having a large number of open holes and sintered for carrying an active material. SOLUTION: A generating element 2 is housed in a battery can 1 and this can 1 is filled with an electrolyte. The can 1 is then internally sealed with a battery cover 3 via an insulator. The element 2 is formed, so that a strip type positive and negative electrodes 4 and 5 are respectively wound via a strip type separator 6. The electrodes 4 and 5, and the separator 6 are wound so as to be slightly dislocated from one another vertically. Only the upper edge of the positive electrode 4 is thereby projected from the upper end of the element 2, while only the lower edge of the negative electrodes 5 is projected from the lower end of the element 2. An upper current collection plate is then welded to the upper edge of the positive electrode 4, and a lower current collection plate 8 to the lower edge of the negative electrode 5. In addition, the current collecting plate 8 is connected to the reverse side of a battery cover 3 and the inner bottom of a battery can 1 via a lead piece or the like. According to this construction, the center projection of the battery cover 3 comes to function as a positive terminal, and the bottom of the battery can 1 comes to function as a negative terminal respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for producing a battery electrode in which an active material is supported on a three-dimensional porous body such as a foamed metal or a nonwoven metal.

[0002]

2. Description of the Related Art In some cases, a three-dimensional porous body such as a foamed metal or a non-woven metal is used as an electrode of a battery in order to increase the density of an active material and increase the battery capacity. For example, foamed nickel (foamed metal), nickel fiber felt (non-woven metal), or the like is used for the positive electrode of a nickel-hydrogen secondary battery. Nickel foam is nickel foam that is made conductive by adding carbon and then baked to remove urethane and carbon components, leaving only foamed metallic nickel. A large number of nickel skeletons are three-dimensionally connected to each other in a network (network) to form a three-dimensional porous body having extremely large porosity. Nickel fiber felt is made by thinning nickel fine fibers produced by chatter vibration or the like into a felt shape (nonwoven fabric shape). In this case, too, a large number of nickel fiber pieces are three-dimensionally networked with each other. A three-dimensional porous body having an extremely large porosity is formed. Therefore, if a powder (insoluble) of, for example, nickel hydroxide, which is an active material, is dispersed in a dispersion medium such as water and applied to these three-dimensional porous bodies and dried, a large number of skeletons and fibers bonded in a network form can be obtained. Since a large amount of the active material can be reliably carried in the gaps, and the active material filling density can be improved, the battery capacity is greatly increased.

Meanwhile, in order to connect the three-dimensional porous body to a terminal of a battery, it is necessary to collect power through a current collector formed of a metal plate or the like. However, welding and connecting the current collector directly to the three-dimensional porous body carrying the active material may prevent the active material from welding, or reduce the mechanical strength of the skeleton or fibers of the three-dimensional porous body. Difficult for.

[0004] Therefore, conventionally, a part of the three-dimensional porous body is pressed in advance and then the active material is supported, and a current collector is welded or crimped to the pressed part. That is, when the three-dimensional porous body is pressed, the skeleton or the fiber of the pressed portion is pressed to form a metal plate, so that the active material hardly adheres. Therefore, even after the active material is supported on the three-dimensional porous body, the current collector can be welded to the pressed portion, and reliable connection can be performed. Further, there is a case where the active material is once carried on the three-dimensional porous body, and then the active material is removed by applying ultrasonic vibration to a part of the three-dimensional porous body, and the current collector is welded to the removed part. Was.

[0005] In some cases, a steel strip or the like serving as a current collector is pressed against the entire surface of the three-dimensional porous body supporting the active material.

[0006]

However, conventionally, as described above, the current collector must be welded or pressed by pre-pressing a part of the three-dimensional porous body or removing the active material. In addition, since these steps are required for each electrode, there is a problem that the productivity of the battery is reduced.

In addition, the three-dimensional porous body is such that the skeleton is collapsed or fibers are brought into close contact with each other only by applying a slight pressing force, and the network portion is stretched and thinned as a whole by applying a slight tensile force. The active material cannot be sufficiently supported. In addition, if this pulling force is increased, it is easily torn and cannot be used. For this reason, careful handling is performed in the step of supporting the active material on the three-dimensional porous body, the step of performing other processing, and, in the case of a winding type power generation element, the step of winding the three-dimensional porous body. There is also a problem that it is difficult to improve the productivity of electrode production by a method of continuously transporting and processing the three-dimensional porous body through a line. Moreover, especially when the current collector is welded or crimped to a part of the three-dimensional porous body,
If force is applied to this current collector during battery assembly work, etc.,
There is also a problem that the three-dimensional porous body is easily torn at the welded portion or the crimped portion and is easily cut. Further, when the current collector is attached to a part of the three-dimensional porous body in this way, there is also a problem that the electric resistance of the current collection increases because the contact area between the current collector and the three-dimensional porous body is small. Was.

When a steel strip or the like is directly pressed into contact with a three-dimensional porous body supporting an active material, the contact resistance with the steel strip or the like becomes unstable due to the active material, and a reliable electric connection is not always ensured. There was also a problem that it could not always be obtained.

The present invention has been made in view of the above circumstances, and has been proposed to improve the productivity of electrodes by sintering a three-dimensional porous body on a conductive thin plate and then supporting an active material. It is an object of the present invention to provide a method of manufacturing a battery electrode that can easily handle a porous body and reliably collect electricity through a conductive thin plate.

[0010]

That is, in order to solve the above-mentioned problems, the present invention is to bond a sheet-shaped three-dimensional porous body to the surface of a conductive thin plate having a large number of openings and sinter the sheet. It is characterized by including a three-dimensional porous body sintering step and an active material supporting step of supporting an active material on the three-dimensional porous body sintered on the conductive thin plate by the three-dimensional porous body sintering step.

According to the means, since the three-dimensional porous body before supporting the active material is sintered into a conductive thin plate, a very large number of fiber pieces and skeletons are formed on the conductive surface at the contact surface of the three-dimensional porous body. And a reliable electrical connection can be obtained. In addition, since the three-dimensional porous body carries the active material in a state of being sintered and bonded to the conductive thin plate, the conductive thin plate is used as a support to facilitate handling such as transport and winding. Moreover, the step of pre-pressing a part of the three-dimensional porous body for each electrode or removing the active material and welding the current collector before performing winding or the like can be omitted, so that the production of the battery can be omitted. Performance can be improved.

[0012] Further, the three-dimensional porous body sintering step is to bond a sheet-shaped three-dimensional porous body to both the front and back surfaces of a conductive thin plate having a large number of openings, and to sinter the three-dimensional porous body. Features.

According to the means, since the three-dimensional porous body is bonded to both sides of the conductive thin plate by sintering, the electrolyte can easily contact the three-dimensional porous body also on the back side of the conductive thin plate. In addition, in the case of using a nonwoven fabric-shaped three-dimensional porous body, the fiber pieces of the front and back three-dimensional porous bodies are entangled through the openings of the conductive thin plate, so that the bonding strength of these three-dimensional porous bodies is increased.

Further, the method further comprises a pressing step of pressing a part of the three-dimensional porous body sintered on the conductive thin plate in the three-dimensional porous body sintering step to the conductive thin plate side. The active material is supported on the three-dimensional porous body which has been sintered into a conductive thin plate and partially pressed in this pressing step. It is characterized by having a cutting step of cutting together with the conductive thin plate at the pressed portion.

According to the means, when a part of the three-dimensional porous body is pressed in the pressing step, the pressed part becomes a metal plate and no active material is supported. Therefore, when a plurality of electrodes are manufactured in a lump and cut at the pressed portion of the three-dimensional porous body by a cutting process, a current collector or the like can be easily connected to the pressed portion of each slice by welding or the like.

[0016]

Embodiments of the present invention will be described below with reference to the drawings.

1 to 7 show an embodiment of the present invention. FIG. 1 is a perspective view showing a method for manufacturing a positive electrode.
Is a longitudinal sectional view showing the structure of the nickel-metal hydride secondary battery, FIG. 3 is a perspective view showing the structure of the positive electrode, FIG. 4 is a perspective view showing the structure of the negative electrode, FIG. 6 is a perspective view showing another manufacturing method of the positive electrode, and FIG. 7 is a view showing a relationship between a discharge rate and a discharge intermediate voltage.

In this embodiment, a method for manufacturing a positive electrode used for a wound-type power generating element of a nickel-metal hydride secondary battery will be described. As shown in FIG. 2, the nickel-hydrogen secondary battery is one in which a power generation element 2 is housed in a battery can 1, filled with an electrolytic solution, and the inside is sealed with a battery lid 3 via an insulator. The power generating element 2 is configured by winding a strip-shaped positive electrode 4 and a strip-shaped negative electrode 5 via a strip-shaped separator 6.
The positive electrode 4, the separator 6 and the negative electrode 5 are wound while being slightly shifted up and down, so that only the upper edge of the positive electrode 4 protrudes toward the upper end of the power generating element 2, and the negative electrode 5, only the lower edge is projected. An upper current collector 7 is welded to the upper edge of the positive electrode 4 projecting toward the upper end of the power generating element 2, and a lower current collector 8 is welded to the lower edge of the negative electrode 5 projecting to the lower end of the power generator 2. It is connected. The current collector plates 7 and 8 are connected to the back surface of the battery cover 3 and the inner bottom surface of the battery can 1 via lead pieces or the like, so that the central projection of the battery cover 3 serves as a positive electrode terminal. The bottom surface of the battery can 1 serves as a negative electrode terminal. In addition,
A rubber valve body 3a for venting gas is attached to the battery cover 3.

As shown in FIG. 3, the positive electrode 4 has a belt-shaped punched metal 9 and a belt-shaped nickel fiber felt 10 bonded to the surface thereof, and a cathode active material 11 mainly composed of nickel hydroxide supported thereon. . Further, the negative electrode 5 is shown in FIG.
As shown in FIG. 2, a punching metal 12 carries a negative electrode active material 13 mainly composed of a hydrogen storage alloy. Each of these punching metals 9 and 12 is formed by pressing a nickel thin plate into a large number of opening holes 9a (not visible behind the nickel fiber felt 10 in FIG. 3) or opening holes 12a (negative electrode active material in FIG. 4). Thirteen depressions). And the separator 6
Is an insulating nonwoven fabric or the like through which the electrolyte passes, and the electrolyte is
Use caustic aqueous solution.

The negative electrode 5 is prepared by kneading a powder of a hydrogen storage alloy and a binder to form a paste and applying the paste on both the front and back surfaces of a punching metal 12 and drying the same, as shown in FIG. The negative electrode active material 13 is adhered and supported in a thick film shape so as to cover both surfaces of the negative electrode 12 and close the opening hole 12a. However, the negative electrode active material 13 does not adhere to the lower edge of the strip of the punching metal 12, and the lower edge of the punching metal 12 of the negative electrode 5 projects from the lower end of the power generating element 2.
Therefore, the lower current collecting plate 8 can be easily welded to the lower edge of the punching metal 12 to which the negative electrode active material 13 is not attached.

The method for manufacturing the positive electrode 4 will be described in detail.
As shown in FIG. 1, first, a strip-shaped nickel fiber felt 10 is bonded to the surface of the strip-shaped punching metal 9 and sintered (three-dimensional porous body sintering step). That is, the nickel fiber felt 10 is stuck to the surface of the punching metal 9 and pressed lightly, and heated to about 850 to 1000 ° C. Then, an extremely large number of fiber pieces adhere to the surface of the punching metal 9 and the opening edge of the opening 9a due to the surface diffusion and partial melting of nickel on the contact surface of the nickel fiber felt 10, as shown in FIG. Then, the nickel fiber felt 10 is sintered and joined to the punching metal 9 so that it does not come off easily. At this time, by using the nickel fiber felt 10 having a width slightly smaller than the width of the punching metal 9, the nickel fiber felt 10 is joined to the punching metal 9 at least at an upper edge thereof with a certain gap. When the nickel fiber felt 10 is joined to the punching metal 9 in this manner, handling such as transporting and winding is facilitated by using the punching metal 9 as a support, and excessive force is applied to the nickel fiber felt 10 during the operation of the subsequent steps. The risk of stretching or tearing due to the addition of

When the nickel fiber felt 10 is sintered and joined to the surface of the punching metal 9 by the three-dimensional porous material sintering step, a powder mainly composed of nickel hydroxide is dissolved and applied to the nickel fiber felt 10 with water. Then, the positive electrode active material 11 is supported by drying (active material supporting step). That is, a positive electrode active material 11 mainly composed of nickel hydroxide is provided in a gap between many fiber pieces of the nickel fiber felt 10.
Are adhered and carried in large quantities. However, in this case, the positive electrode active material 11 is made of a punched metal 9 which is a nickel thin plate.
Hardly adheres to In this active material supporting step, the nickel fiber felt 10 can be processed by using the punching metal 9 as a support as described above. No decrease in the amount of 11 carried will occur.

The positive electrode 4 manufactured by the above method is shown in FIG.
As shown in FIG. 7, the wound power generating element 2 is wound together with the negative electrode 5 via the separator 6. The upper edge of the positive electrode 4 protruding from the upper end of the power generating element 2 is the upper edge of the punching metal 9 to which the nickel fiber felt 10 is not bonded and the positive electrode active material 11 is not attached. The plate 7 is easily welded.

As described above, according to the method of manufacturing the positive electrode 4 in the nickel-metal hydride secondary battery of the present embodiment, the nickel fiber felt 10 before supporting the positive electrode active material 11 is sintered and bonded to the punching metal 9. Thus, the nickel fiber felt 10 and the punching metal 9 can be reliably electrically connected. Therefore, when the positive electrode active material 11 is supported on the nickel fiber felt 10, stable current collection can be performed from the positive electrode active material 11 by the punching metal 9 via the nickel fiber felt 10. Also, unlike the nickel fiber felt 10, the positive electrode active material 11 does not adhere to the punched metal 9, so that the upper current collector 7 can be easily connected to the upper edge protruding toward the upper end of the power generating element 2 by welding. Connection with the battery cover 3 becomes easy. In addition, since the positive electrode 4 performs operations such as an active material supporting step and a winding step of the power generating element 2 using the punching metal 9 as a support, excessive force is applied to the nickel fiber felt 10 which is difficult to handle by itself. Transport and the like can be performed without any problems, and workability can be improved.

The positive electrode 4 is appropriately processed after a three-dimensional porous material sintering step and an active material supporting step are continuously performed by a line processing for sequentially supplying a band-shaped punching metal 9 and a nickel fiber felt 10 from a roll. It can also be manufactured by cutting to length. At this time, a wide nickel fiber felt 1 is attached to a wide punching metal 9.
0 may be supplied to manufacture a plurality of positive electrodes 4 in parallel. That is, after performing the three-dimensional porous body sintering step by sintering the wide nickel fiber felt 10 to the wide punching metal 9 and performing a three-dimensional porous body sintering process, as shown in FIG. Along the punching metal 9 side (pressing process)
The nickel fiber felt 10 is divided into a plurality of tracks by 0a (in FIG. 6, it is divided into three). Then, after performing an active material supporting step of supporting the positive electrode active material 11 on the nickel fiber felt 10, the punching metal 9 and the nickel fiber felt 10 are pressed along the pressed portion 10a (along the dashed line in FIG. 6). Is cut for each track (cutting step), a plurality of positive electrodes 4 can be efficiently manufactured in parallel. However, at the cut portion of the punched metal 9, the pressed portion 10a of the nickel fiber felt 10 is sintered and joined to the edge of the cut portion without any gap. However, in the pressed portion 10a, a large number of fiber pieces are crushed into a nickel plate shape, and the positive electrode active material 11 hardly adheres even in the active material supporting step, so that the cut portion protrudes from the upper end side of the power generation element 2. Even in the case of the upper edge portion, the upper current collecting plate 7 can be easily welded.

The configuration of the present invention is not particularly limited except for the positive electrode 4 in the above embodiment. That is, the configuration of the negative electrode 5 and the configuration in which the positive electrode 4 and the negative electrode 5 are connected to the positive terminal of the battery lid 3 and the negative terminal of the battery can 1 via the current collector plates 7 and 8 are also limited to those of the present embodiment. Not optional.

Further, in the above embodiment, the nickel fiber felt 10 is sintered only on the surface of the punching metal 9 of the positive electrode 4, but the nickel fiber felt 10, 10 is sintered on both the front and back surfaces of the punching metal 9. You can also. In this case, the electrolyte can be easily brought into contact with the positive electrode active material 11 supported on the nickel fiber felt 10 also on the back side of the punching metal 9. Moreover, since the fiber pieces of the front and back nickel fiber felts 10 and 10 are entangled with each other via the opening 9a of the punching metal 9, the bonding strength of these nickel fiber felts 10 and 10 can be increased.

Further, in the above embodiment, a nickel-hydrogen secondary battery has been described. However, the present invention can be similarly applied to any battery that can use a three-dimensional porous body as an electrode.

Further, in the above embodiment, the nickel fiber felt 10 is used as the three-dimensional porous body. However, the present invention is not limited to this as long as it is a three-dimensionally porous conductor. For example, foamed nickel or the like can be used. . Moreover, the type of the conductor is not limited to such nickel, but can be arbitrarily selected according to the type of the battery or the electrode.

Further, in the above-described embodiment, the punching metal 9 made of a nickel thin plate is used as the conductive thin plate. However, any conductive thin plate having a large number of openings having an arbitrary shape and an arbitrary size can be used. Such as expanded metal or wire mesh, or those with microscopic fine holes formed by compressing foamed metal or non-woven metal into a metal plate. Can also be used. Moreover, the type of the conductor is not limited to such nickel, but can be arbitrarily selected according to the type of the battery or the electrode.

Further, in the above embodiment, the wound power generating element 2 used for a cylindrical battery is shown, but the present invention can be similarly applied to a stacked power generating element 2 used for a prismatic battery. it can. When using a laminated type, punching metal 9
For the nickel fiber felt 10, a flat plate (short sheet) instead of a band (long sheet) is used.

[0032]

EXAMPLES The batteries of the following examples and comparative examples were prepared and compared.

Examples and Comparative Examples Examples: SC type Ni-MH battery Positive electrode dimensions: 188 mm (length) x 31.5 mm (width) x
0.80mm (thickness)-Negative electrode plate dimensions: 235mm (length) x 31.5mm (width) x
0.43 mm (thickness) ・ Electrolyte: 31 wt% (wt%) aqueous solution of potassium hydroxide in which lithium hydroxide (LiOH) is dissolved at 30 g / l ・ Nominal capacity: 2.5 Ah

Comparative Example 1 Positive electrode dimensions: 188 mm (length) x 31.5 mm (width) x
0.76mm (thickness) (active material was removed and current collecting terminals were ultrasonically welded) ・ Other items are the same as in the example

Comparative Example 2 Positive electrode dimensions: 188 mm (length) x 31.5 mm (width) x
0.73 mm (thickness)-Conductive thin plate: 188 mm (length) x 34 mm (width) x 0.
06mm (thickness) (wound with the positive electrode) ・ Other items are the same as in Example 1.

[Comparative Results] When the battery of Comparative Example 1 was manufactured by the conventional manufacturing method, only 5 cells / min (battery for 5 cells per minute) could be manufactured. Since the step of removing the active material for each sheet and the step of welding the current collecting terminals can be omitted, the production of 12 cells / min can be performed in each case, and the productivity is improved.

The batteries of Example and Comparative Example 2 were:
FIG. 7 shows the results of measuring the discharge intermediate voltage while changing the discharge rate. When the discharge rate of the battery increases, the voltage drop due to the internal resistance of the battery increases, so that the discharge intermediate voltage decreases. In the embodiment, the three-dimensional porous body of the positive electrode is sintered on the conductive thin plate, whereas in the comparative example 2, the three-dimensional porous body is only in contact with the conductive thin plate. Become. Therefore, the battery of the example is the same as that of the comparative example 2.
As compared with the battery of Example 1, even if the discharge rate was increased, the rate of decrease in the discharge intermediate voltage was reduced, and high current collecting properties could be obtained.

[0038]

As is apparent from the above description, according to the battery electrode manufacturing method of the present invention, a three-dimensional porous body can be sintered into a conductive thin plate to obtain a reliable electrical connection. Through this conductive thin plate, stable current collection can be performed. Moreover, the step of pre-pressing a part of the three-dimensional porous body for each electrode or removing the active material and welding the current collector before performing winding or the like can be omitted, and the conductive thin plate can be formed. Since the three-dimensional porous body can be subjected to an active material supporting step or the like without being stretched or cut by performing transport or the like as a support, productivity of the electrode can be improved.

When the three-dimensional porous body is sintered and bonded to both sides of the conductive thin plate, the utilization factor of the back side of the electrode surface can be increased. In addition, when a nonwoven fabric-shaped three-dimensional porous body is used, the fibers are entangled with each other through the openings of the conductive thin plate, so that the bonding strength is increased.

Furthermore, if the three-dimensional porous body is pressed before the active material is supported, a current collector or the like can be easily connected to the pressed portion, so that a plurality of electrodes can be manufactured and cut at once. , And can be efficiently manufactured by line processing or the like.

[Brief description of the drawings]

FIG. 1, showing an embodiment of the present invention, is a perspective view illustrating a method for manufacturing a positive electrode.

FIG. 2, showing one embodiment of the present invention, is a longitudinal sectional view illustrating a structure of a nickel-metal hydride secondary battery.

FIG. 3, showing one embodiment of the present invention, is a perspective view illustrating a configuration of a positive electrode.

FIG. 4 illustrates one embodiment of the present invention, and is a perspective view illustrating a configuration of a negative electrode.

FIG. 5, showing an embodiment of the present invention, is a perspective view illustrating a method for manufacturing a power generating element.

FIG. 6, showing an embodiment of the present invention, is a perspective view illustrating another method for manufacturing a positive electrode.

FIG. 7 is a diagram showing a comparison result between an example of the present invention and a comparative example, and is a diagram showing a relationship between a discharge rate and a discharge intermediate voltage.

[Explanation of symbols]

 4 Positive electrode 9 Punching metal 9a Opening hole 10 Nickel fiber felt 11 Positive electrode active material

Claims (3)

[Claims] 1. A three-dimensional porous body sintering step of laminating and sintering a sheet-like three-dimensional porous body on the surface of a conductive thin plate having a large number of openings, and the three-dimensional porous body sintering step. An active material supporting step of supporting an active material on a three-dimensional porous body sintered on a conductive thin plate. 2. The three-dimensional porous body sintering step is characterized in that a sheet-like three-dimensional porous body is bonded and sintered on both front and back surfaces of a conductive thin plate having a large number of openings. The method for producing a battery electrode according to claim 1. 3. A pressing step of pressing a part of the three-dimensional porous body sintered on the conductive thin plate in the three-dimensional porous body sintering step toward the conductive thin plate side, wherein the active material supporting step includes: The three-dimensional porous body sintered on a conductive thin plate and partially pressed in this pressing step carries the active material. The three-dimensional porous body carrying the active material in the active material supporting step is pressed. The method for producing a battery electrode according to claim 1 or 2, further comprising a cutting step of cutting the portion together with the conductive thin plate.