JPS593027B2 - Cathode for alkaline batteries - Google Patents

Description

[Detailed description of the invention] The present invention uses a cathode active material such as zinc as a cathode current collector.

The present invention relates to a method for manufacturing a cathode for an alkaline storage battery having a structure in which the cathode is attached. An alkaline battery is a secondary battery that can be charged and discharged, and is made up of negative and positive electrodes, such as zinc as the negative active material and nickel oxide or silver oxide as the positive active material, and a caustic potash solution as the electrolyte. be.

The cathode conventionally used for alkaline batteries consists of a cathode active material applied as a sticky mixture to a cathode current collector using a binder such as polyvinyl alcohol, polystyrene, or polyacrylate. .

However, with any cathode using a conventional binder, satisfactory performance as an alkaline battery cannot be obtained.

For example, when polyvinyl alcohol is used, it gradually deteriorates in a concentrated alkaline solution, causing the active material to fall off from the current collector. In addition, when polyolene is used, its high electrical resistance increases the internal resistance of the battery, and if the mixing ratio is reduced to reduce this, it has disadvantages such as insufficient strength. Not good. Furthermore, when polyacrylate is used, repeated charging and discharging to dissolve it in the electrolyte can deform the electrode and cause short circuits. It is unsuitable for constructing a cathode for a real alkaline battery. In the present invention, a mixture consisting of a cathode active material, an aqueous dispersion of a fluororesin, and alkali-resistant short fibers is developed to obtain a fibrous sheet body, and then the fibrous sheet body is laminated and developed so that the directions of the fibrous sheet bodies are different. However, by attaching multiple layers of fibrous sheets to the current collector, it is highly flexible and does not deform during long charge/discharge cycles, and it also improves the efficiency of alkali-resistant battery reactions. An object of the present invention is to provide a manufacturing method that allows a cathode for an alkaline storage battery with excellent properties to be obtained.

In other words, in the method of the present invention, due to the synergistic effect of mixing short fibers, kneading and spreading an aqueous fluororesin dispersion, and laminating them in different directions of spreading, a fibrous sheet with intricately interwoven structures is produced. is obtained, and the flexibility and mechanical strength are significantly improved.

In addition, the electrode reaction surface area is significantly increased (2 times larger, battery reactions are carried out efficiently and uniformly, and the products generated by the battery reactions can be retained near the electrodes, allowing for multiple charge/discharge cycles, etc.) Accordingly, an excellent cathode for an alkaline storage battery can be obtained without causing deformation even when the present invention is used.Examples of the present invention will be described in detail below.

In the method for producing an alkaline storage battery cathode of the present invention, when zinc is used as the active material, an aqueous dispersion of fluororesin (dice version) is added to 100 f of the zinc active material, 0.5 t of short fibers of 8 f1 polyamide, and 30 liters of water are added. The mixture was kneaded for about 15 minutes in a seconder mixer to form a clay-like material, and this material was rolled by rollers to form a sheet. In this sheet body, the fibrous bodies of fluororesin are aligned in the rolling direction, that is, the longitudinal direction of the fibrous bodies, so a plurality of sheet bodies are made and the alignment directions of the fibrous bodies are different so that they are orthogonal to each other. , overlap and roll again with rollers. This rolling operation is repeated to form a sheet of active material having sufficient strength, and this is pressed onto the cathode current collector to complete the cathode. }, alkali-resistant short fibers are not limited to polyamide, but also include polyethylene, polypropylene, acrylic [
It may also be a copolymer of carbon fiber and pinyl chloride. If the length of the short fibers is too short, it will have little effect in preventing deformation of the electrode, and if it is too long, it will cause cross-wires and difficulties when rolling out. 15m! Appropriate length, preferably 5m
If the amount of short fibers is too large, it becomes difficult to form a multilayer structure of the active material sheet, so the appropriate amount is about 0.5 (!l) for the active material.

Assemble the cathode thus obtained with a nickel-zinc alkaline secondary battery and repeat the charge-discharge cycle of charging at a 5-hour rate and discharging at a 5-hour rate with the zinc electrode utilization rate at 30%. As a result, characteristics as shown by solid line 1 in FIG. 1 were obtained.

In order to compare with this characteristic, solid line 2 shows the case where the zinc active material is not mixed into the short fibers, and the zinc active material is 100% (8V for It, polypinial alcohol is added, and 80t of water is added to form a paste and applied to the current collector. The case of the conventional battery configured is shown by solid line 312.As is clear from this figure, it is clear that the battery using the cathode of the present invention has the most charge/discharge cycles.The utilization rate of the zinc electrode is 60%. In this case, the characteristics shown by the dotted line will be obtained, and the effect of the present invention will become even clearer.} When measuring the special notes in Figure 1, in order to avoid the influence of the opposite electrode, A large excess of nickel electrodes was used, and 8M caustic potassium was used as the electrolyte.

[Brief explanation of the drawing]

FIG. 1 is a comparison diagram of the characteristics obtained in the example of the present invention and the characteristics obtained in the reference example and the conventional example.

Claims (1)

[Claims] 1. A step of developing a kneaded material consisting of a cathode active material, an aqueous dispersion of a fluororesin, and alkali-resistant short fibers to obtain a fibrous sheet body, and stacking and developing the fibrous sheet bodies so that the directions of the fibrous sheet bodies are different. A method for producing a cathode for an alkaline storage battery, comprising the step of attaching a fibrous sheet body laminated in multiple layers to a current collector.