JPH0415582B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a method of manufacturing an electrode plate for a battery. [Background Art] For example, nickel anode plates used in alkaline storage batteries are mainly produced by a sintering method. This method is known to have excellent mechanical strength, as well as excellent performance in terms of high rate discharge characteristics and cycle life, but the problem is that the manufacturing process is complicated and it takes a long time. There is. As a manufacturing method that solves these manufacturing problems, there is a known method of applying and drying an active material paste to the core of an electrode plate such as a punched plate, but in terms of performance, sintered electrode plates are not suitable. It is several steps inferior to . Therefore, in recent years, a manufacturing method has been proposed in which a metal porous body having three-dimensionally continuous pores is used as a substrate and an active material is held on this substrate. According to this method, the manufacturing process is simple, It has been confirmed that the manufacturing time is short, and the performance is equivalent to, or in some cases even better than, sintered electrode plates. To explain a specific example of this manufacturing method using a nickel anode plate as an example, a glue liquid is added to a mixed powder of nickel hydroxide powder and conductive agent powder to form a paste, and this paste is applied to the pores of the nickel porous body. The active material may be introduced by mechanical means, ultrasonic vibration or vacuum degassing, and then dried and pressurized to form a completed electrode plate, or after pressurization, polyester may be applied to the surface of the substrate to prevent the active material from falling off. The completed electrode plate is impregnated with a suspension of tetrafluoroethylene and dried.
Although this manufacturing method is simpler than the conventional sintering method, it cannot be said to be a fully streamlined manufacturing method, and the process of filling the pores of the substrate with a paste-like active material is difficult. However, it is difficult to pack them uniformly and densely. Furthermore, a filling method in which a substrate made of a metal porous body having three-dimensionally continuous pores is preliminarily impregnated with a liquid, and a paste-like active material is rubbed into the pores of the substrate is disclosed in JP-A-53-10833. and Japanese Patent Publication No. 54-63230
It is disclosed in the publication No. However, according to these manufacturing methods, since the paste mixes with the liquid in the pores, the density of the active material and the fluidity of the paste change over time, making it difficult to adjust the filling amount, and the liquid content of the paste changes over time. Since the rate increases, there are problems such as a decrease in the amount of filling. Furthermore, since the active material paste is made viscous by using a glue liquid, the binding force between the active material powders is strong, increasing the resistance when filling the holes in the substrate. [Disclosure of the Invention] The present invention was invented in view of the above points, and includes a substrate made of a metal porous body having three-dimensionally continuous pores containing a liquid, and then an active material powder is injected into the pores. It is characterized by being filled with. That is, the active material in the pores is filled in a powder state, and the powder particles are independent and can move freely.The active material powder is placed on the surface of a porous substrate containing a liquid. First, the active material powder is filled into the pores of the substrate by settling. The filled powder absorbs the liquid in the substrate, so the amount of liquid gradually decreases. In other words, as the amount of powder packed increases, the relationship between the powder and liquid changes from the initial state through the slurry region and capillary to the funicular region, as shown in the drawing, and the powder loses its fluidity and becomes fixed in the pores. be done. In the drawings, 1 is a powder particle, 2 is a liquid, 3 is a liquid film, and 4 is a hole. If the powder is simply supplied onto the base from the middle of the slurry region, the pores will not be filled, and it will be necessary to press-fit the powder by sliding or other methods. In addition, during filling, the powder supply speed becomes faster than the filling speed into the holes, causing a difference in the degree of filling between the deep part of the hole and the surface part, resulting in a decrease in the amount of liquid at the surface part. However, because the liquid is supplied from deep by capillary action and fluidity is ensured,
Filling becomes relatively uniform between the surface and deep areas. Furthermore, when a powder is moistened, its apparent volume decreases and its apparent density increases, so even if the substrate has the same porosity, it is difficult to fill a dry powder into a dry substrate that does not contain liquid. In comparison, the amount of filling can be increased. As described above, the present invention has the advantages of the dry method, which reduces the interaction between the particles of the powder to be filled and makes the filling easy and uniform, and the method which increases the filling amount and fixes the powder particles inside the pores. It has the advantage of easy wet method. As shown in Table 1, the present inventor actually carried out filling under various conditions and studied the optimum liquid content of the substrate. Nickel hydroxide with a mesh pass of 200 was used as the active material powder, a porous nickel material with a porosity of 95%, a pore diameter of 100 to 300 μm, and a thickness of 2.0 mm was used as the substrate, and water was used as the liquid. Further, in the "Condition" column of Table 1, "single-sided filling" means that the active material powder is filled from one side of the substrate, and "both-sided filling" means that the active material powder is filled from both sides of the substrate. From Table 1, it can be seen that the higher the moisture content, the higher the filling rate, and that filling from both sides increases the filling rate even when the moisture content is low. The density of the powder used in the experiments shown in Table 1 is 0.85 g/cm ³ , but we were able to achieve a higher packing density than this (No. 1,
No. 4, No. 5). Regarding the relationship between the powder particle size and the pore size, it is desirable that the powder particle size be 1/2 or less of the pore size, based on the experimental results that showed that if the particle size was 150 μm or less, filling could be performed without any problem. Furthermore, regarding the uniformity of filling, there was variation between the surface and deep part of the hole in No. 3 in Table 1, and between the surface and center in No. 6, but otherwise it was uniform. It was filled with.

[Example and comparative example]

Example 1 A substrate made of a nickel porous body containing water with a porosity of 95%, a thickness of 1.3 mm, and a water content of 80%, having three-dimensionally continuous pores with a pore diameter of 100 to 300 μm, is placed horizontally. On this substrate, 200 mesh passes of mixed powder consisting of 95 parts of nickel hydroxide powder and 8 parts of cobalt hydroxide are gradually supplied. When this mixed powder no longer enters the pores naturally, the fluidity of the filler in the pores, which was press-fitted with a spatula-shaped sliding tool, disappears and the mixed powder supply and filling operation are terminated when it reaches the funicular region. . After drying, a binding liquid was added, and after drying again, pressure pressing was performed. Example 2 In Example 1, a fluororesin solution was used as the liquid to be contained in the substrate, and immediately after the mixed powder was filled and dried, it was pressed under pressure. Example 3 In Example 2, the liquid content of the substrate was set to 65% by volume, and the mixed powder was filled from both sides of the substrate. Comparative Example 1 An active material paste was prepared by mixing the same mixed powder as in Example 1 with a 2% aqueous solution of carboxymethylcellulose as a glue at a ratio of 7:3. Using the same substrate as in Example 1, a base plate was rubbed in with a spatula-shaped jig without containing a liquid plate. After drying, a binding liquid was added, and after drying again, pressure pressing was performed. Comparative Example 2 In Comparative Example 1, a substrate containing water with a water content of 30% by volume was used. Table 2 shows a comparison of the filling rate and production time in these Examples and Comparative Examples. In this table, the post-process time indicates the time for the binding liquid addition process, drying process, pressing process, etc. after filling. From Table 2, it can be seen that each Example has a higher filling rate and a shorter required manufacturing time than each Comparative Example. Further, the nickel anode plates obtained in the Examples and Comparative Examples were each combined with a well-known cadmium cathode plate, and the capacity was measured in an aqueous caustic potassium solution to obtain the data shown in Table 3.
From this table, it can be seen that each Example is superior in utilization rate and volumetric efficiency as compared to the Comparative Example.

【table】

[Industrial applicability]

The manufacturing method according to the present invention is not limited to the nickel anode plate shown in the example, but can also be applied to a substrate made of a metal porous body having three-dimensionally continuous pores, including a cadmium cathode plate. It can also be applied to the production of electrode plates for other battery systems, which serve as bodies and active material holders.

[Brief explanation of drawings]

The drawing is a schematic diagram explaining the relationship between the powder and liquid to be filled, where is the initial state, is the slurry area,
indicates the state of the capillary region, and indicates the state of the funicular region.

Claims (1)

[Claims] 1. A method for producing a battery electrode plate, which comprises impregnating a liquid in a substrate made of a pair of metal porous holes having three-dimensionally continuous pores, and then filling the pores with active material powder.