JPH0239064B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a battery electrode plate, in which a sponge-like metal porous body having a three-dimensionally continuous network structure is filled with an active material in the form of a paste. The purpose of this is to fill a long band-shaped sponge-like porous metal body (hereinafter referred to as porous body) with an active material in the form of a paste in the manufacturing process of an electrode plate. It is an object of the present invention to provide a method for manufacturing an electrode plate that is excellent in mass productivity by providing a step of preliminary pressing using a roller press and subsequent main pressing using a flat plate press after filling and before a drying step. That is, by adjusting the liquid content in the porous body in the preliminary press to an amount suitable for the main press, it is possible to make the pressurizing process continuous. In addition, the pressurizing process eliminates the opportunity for the binder to adhere to the press mold as an additive for the binder, thereby reducing maintenance work for the pressurizing device. Conventionally, as an electrode plate for a battery, a method has been adopted for lead-acid batteries, in which a porous cylinder or a grid is filled with a powder mainly containing an active material, or a method is applied in the form of a paste. On the other hand, in the case of a nickel-cadmium storage battery, which is an alkaline battery, a method similar to the above or a method of impregnating a sintered body with a salt solution of the active material and converting it into an active material by electrolysis, thermal decomposition, chemical treatment, etc. It has been adopted. In order to retain an active material in a sintered body using such a method, it is necessary to repeat impregnation with a salt solution and conversion several times to more than 10 times, making the process complicated. On the other hand, in the case of applying the paste to the grid, the manufacturing method is simpler than in the case of holding it in a sintered body, and it is possible to use a screen, expanded metal, perforated plate, etc. as the support. , a continuous manufacturing method was also possible. However, the number of contact points between the support and the active material is smaller than in the case of a sintered body, and the bonding strength is also insufficient, so that the battery characteristics such as discharge performance and lifespan are not as good as those of a sintered body. Note that if a sintered body is used as the support and a coating method can be adopted, the advantages of both can be utilized, but in the conventional sintered body, the pore diameter is small, ranging from several microns to several tens of microns. On the other hand, the active material used for diameter filling has a size of several microns to several hundred microns, and it has been impossible to uniformly fill the sintered body directly to the inside of the sintered body. However, the sponge-like porous metal bodies that have recently been commercialized are porous bodies in which spherical pores are three-dimensionally connected, and the pore diameter can be arbitrarily selected within the range of several tens of microns to several mm. Therefore, if the support is a sponge-like metal porous material having a pore size that matches the particle size distribution of the active material to be filled, the coating method can be adopted. In other words, if a mixture of an active material, a conductive material, and an additive is filled in a paste form inside a sponge-like porous metal material, the active material is directly filled in the form of the active material, unlike when it is added in the form of a salt. The manufacturing process can be simplified without the need for conversion treatment. As an application example of this method, we have proposed a nickel positive electrode for alkaline storage batteries. In the case of a nickel positive electrode, the active material nickel hydroxide is used as a powder with a particle size distribution of several microns to 200 microns, which is mixed with nickel powder and cobalt powder to form a paste and formed into a sponge-like material with pore sizes ranging from several tens of microns to several hundred microns. After filling the inside of the metal porous body, it is dried, added with a binder, and pressurized to form an electrode plate. A nickel-cadmium storage battery constructed with this positive electrode and a cadmium negative electrode can have characteristics equivalent to or higher in capacity than a battery constructed using a conventional nickel electrode using a sintered body as a support. However, electrode plates were manufactured through the following steps, but the drying and pressurizing steps were not necessarily suitable for mass production. In other words, filling the porous body with paste and drying (completely dry) adding the binder and drying (semi-drying)
It was manufactured through a pressure process using a flat plate press. If drying is completely carried out during this pressurization, there is a risk that the sponge skeleton will be destroyed during pressurization.Therefore, for pressurization, a binder is added, and then drying is performed to adjust the water content to a value suitable for pressurization, that is, 15~ It was done after adjusting the moisture content to 20%. However, at this time, the thickness of the porous body,
Changing the moving speed requires setting appropriate drying conditions, which is complicated. Moreover, since it is not always possible to adjust the water content to an optimal value, there are cases where an adjustment step is required as a pretreatment during pressurization. The porous material is sandwiched between water-absorbing cloth or paper and pressurized to bring the water content to an optimum value. Therefore, the pressurizing process takes a lot of time, the work is done intermittently, and the drying process before that is complicated, so it is not suitable for mass production, and improvements are desired. was. The present invention focused on the fact that when a porous body filled with a paste-like active material is subjected to appropriate pre-pressurization, its liquid content can be adjusted to a value suitable for main pressurization. That is, when a porous body filled with a paste-like active material is pressurized, liquid is discharged from the porous body, and the amount thereof is proportional to the degree of pressurization. For example, in the case of a nickel electrode, if a porous body with a porosity of 95% is filled with a paste with a liquid content of approximately 30%, the liquid content will be reduced by applying pressure to a thickness of about 80% of the thickness of the porous body at the time of filling. 15-20 optimal for pressure
It has been found that it can be adjusted to %. The preliminary pressurization is performed using a roller press because it is possible to continuously pressurize a long porous body filled with active material, and it is easy to remove liquid coming out of the porous body and remove deposits from the press surface. It has been found that a method using a flat plate press is suitable for the main pressing. In other words, the capacity density of the porous body filled with active material in paste form is approximately 350 mAh/cm ³ , and the finished electrode plate is approximately 500 mAh/cm ³ . When pressurized at 450 mAh/cm ^{3 , no problems occur up to around 450 mAh/cm 3} , but when pressurized to a capacity density higher than that, the porous material stretches and cracks occur, and rollers are not used for main pressurization. It is not appropriate to employ a press. Therefore, it was found that the best method is to use a roller press for preliminary pressing and a flat plate press for main pressing. Next, in the production of electrode plates, the porous body is pressurized either immediately after filling with paste or after adding the binder in the conventional manufacturing method; in the former case, since the porous body does not contain a binder, it There is almost no active material adhesion, and even if it does, it is easy to remove. Furthermore, since a portion of the liquid in the porous body is removed by pressurization, the drying efficiency is higher than that of the latter. on the other hand,
In the latter case, the mixture of active material and binder adheres to the pressurized surface, which requires removal work, and the porous material is dried with a large amount of liquid, so energy consumption is higher than in the former case. Become. Therefore, it is better to apply pressure immediately after filling the paste. Hereinafter, a nickel pole will be described as a specific example. Example A sponge-like porous body made of nickel and having a structure shown in FIG. 1 with a thickness of 1.0 mm, a porosity of 95%, and a pore diameter of 50 to 300 μm was used as the support for the active material. In the figure, numeral 1 is a core portion of nickel, and numeral 2 is a hole portion. A mixture of 85wt% nickel hydroxide, 10wt% nickel powder, and 5wt% cobalt powder was added to the above porous body.
Fill it uniformly with a 0.5% cyclomethylcellulose (CMC) aqueous solution into a paste with a moisture content of approximately 30wt%.
The paste attached to the surface was removed to obtain an active material-filled porous body. This porous body has an active material with a water content of approximately 30%, a porosity of approximately 5%, and a sticky surface. Cut this into a size of 200 x 500 mm,
Electrode plates were prepared using the present invention and conventional methods. First, an electrode plate was manufactured by the method of the present invention shown in A of FIG. 2 by gradually changing the conditions of preliminary pressing using a roller press, and the state of the porous body was observed. The results are shown in Table-1. As is clear from the table, the pressure applied by the roller press is line pressure unlike the flat plate press, so it is easy to damage the porous material, and the safe degree of pressure is 450 mAh / It is around cm ³ , and if it is more than that, cracks and cuts will occur. Therefore, the pressure applied by the roller press is approximately 80% of the thickness when filling the paste.
% thickness.

【table】

[Table] Next, main pressurization was performed using a flat plate press, followed by drying, addition of a binder (tetrafluoroethylene suspension), drying,
An electrode plate having a thickness of 0.7 mm was obtained by the method of the present invention. On the other hand, the production of an electrode plate by the conventional method shown in FIG. 2B involves completely drying a porous body filled with an active material.
After addition of a binder and semi-drying, the mixture was pressed and dried using a flat plate press to obtain a 0.7 mm electrode plate. In this case, the total drying time required to obtain the electrode plate is at a temperature of 100%.
While it took about 18 minutes at ℃, the method of the present invention significantly shortened the time to about 10 minutes under the same conditions. In addition, in the conventional manufacturing method, the binder and active material adhered to the pressure mold during pressurization, and it was necessary to remove the deposits each time pressurization was applied, but in the case of the present invention, when pressurization, the porous mold Since it does not contain a binder, the active material that adheres to the pre-pressurized roller press can be easily removed.
There was almost no adhesion to the flat plate press of this pressurization, and even if it did adhere, it could be easily removed and almost no maintenance work was required. By manufacturing an electrode plate according to the manufacturing process of the present invention, it has become possible to improve efficiency by about 20% compared to conventional manufacturing methods. Next, using these electrode plates as the positive electrode and a cadmium electrode as the negative electrode, six AA and sealed nickel-cadmium storage batteries were manufactured. A battery using the electrode plate manufactured by the method of the present invention is designated as a, and a battery manufactured using the conventional method is designated as b. The battery is charged at 1/10C,
The initial capacity is 2470.
~2580mAh, b2460~2580mAh, now a2400~2520mAh after about 500 charge/discharge cycles,
b2400 to 2500mAh, there was almost no performance deterioration in any of the batteries, and no influence of changing the pressurization timing in electrode plate manufacture was observed. As described above, the present invention has the following excellent effects. (a) Before the main pressurization, preliminary pressure is applied using a roller press that is ideal for prepressing, so the 15
It is possible to easily and reliably adjust the liquid content to ~20%, and not only can continuous operation be performed, but also it is easy to remove deposits from the press surface. (b) Since the main pressing is performed using a flat plate press, the thickness of the electrode plate can be made uniform and the surface condition can be arbitrarily determined. (c) By combining preliminary pressurization with a roller press and main pressurization with a flat plate press, it is possible to manufacture electrode plates of high quality with extremely high efficiency.

[Brief explanation of drawings]

Fig. 1 is an enlarged view of a sponge-like porous metal body used in an embodiment of the present invention, Fig. 2A is a schematic diagram of the manufacturing process of an electrode plate showing an embodiment of the present invention, and Fig. 2B is a conventional FIG. 2 is a schematic diagram of the manufacturing process of an electrode plate showing the manufacturing method of FIG. 1...Nickel in the core part, 2...Void part.

Claims (1)

[Claims] 1. In a battery electrode plate that uses a sponge-like porous metal material as a support for an active material, after filling the inside of the porous material with the active material in paste form, the material is pressed using a roller press and then a flat plate press before the drying process. A method for manufacturing an electrode plate for a battery, characterized by providing a process.