JPS6355186B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in spiral shaped electrodes for batteries.

Cylindrical sealed batteries with coiled electrode plates are most widely used as power sources for various electronic devices, and there is a strong demand for higher capacity and lower costs for these batteries. A typical sealed battery is a nickel-cadmium storage battery, and its electrodes are
Generally used are a sintered electrode in which a sintered substrate is filled with an active material by electrolysis, and a spaced electrode in which an active material paste containing a binder is applied to a perforated plate.

Sintered electrodes have excellent performance, but their capacity and
Paste electrodes are superior in terms of cost. However, paste-type electrodes are inferior in lifespan and utilization rate, especially in the positive electrode.

As a method to improve this problem, an electrode using a sponge-like porous metal material having a three-dimensional structure as an active material holder has been proposed. This porous material can be freely obtained with pore diameters in the range of several tens of micrometers to 500 micrometers, and can be filled directly with paste-formed active material at high density, with little active material falling out, resulting in low cost. High capacity electrodes can be expected.

However, when an electrode using this sponge-like porous material is spirally wound, cracks may occur, which may lead to breakage of the electrode. Especially when starting winding, the smaller the winding diameter, the more likely cracks will occur.

The present invention solves these problems,
The material is characterized in that the part of the sponge-like porous metal material corresponding to the electrode winding start end is compressed under pressure to make it have a lower porosity than other parts and filled with an active material, and then the entire part is compressed under pressure. be.

According to the present invention, the part corresponding to the winding start end of the porous body is filled with the active material in a state of low porosity, so the amount of active material relative to the skeleton of the porous body is reduced, and the stretchability of the skeleton is increased. Therefore, cracks are less likely to occur during spiral winding.

The present invention will be explained below with reference to Examples.

Figure 1 shows the schematic structure of a sponge-like porous metal body, in which a three-dimensionally continuous lattice 1 provides
Similarly, a three-dimensionally continuous space 2 is formed, and the active material is held within this space.

Figure 2 shows a long band-shaped sponge-like porous metal body for continuously manufacturing a large number of electrode plates. has been established. 5 is a highly porous part that is not compressed. The compressed portion 4 may be compressed from both sides as shown in FIG. 3, or from one side as shown in FIG. After this porosity is filled with a paste-like active material during the process of transporting it in its length direction, it is cut into electrodes of a predetermined size at the positions indicated by the dashed lines in the figure.

FIG. 5 shows the electrode made as described above, where 6 corresponds to the low porosity section 4, and when the electrode is configured in a spiral shape, the winding starts from this section. 7 corresponds to the highly porous portion 5. 8 is a lead piece connected by welding.

FIG. 6 shows a state in which the positive electrode plate 9 configured as described above, a negative electrode plate 10 and a separator 11 are combined and started to be wound in a spiral shape.

A sponge-like porous body can be manufactured, for example, as follows. First, a conductive material is attached to a continuous band-shaped sponge-like sheet of polyurethane, and then the sheet is nickel-plated through an electrolytic bath using a Watt bath. Thereafter, the resin is roasted to remove the resin and heat treated in a hydrogen stream.

Specific examples will be described below.

As described above, a sponge-like porous nickel material with a thickness of 1.5 mm, a width of 150 mm, and a porosity of approximately 94% was produced. Next, the end portions of this band-shaped porous body were compressed under pressure to provide a low-porosity portion. The porosity of the compressed part is 91
It was %.

Next, the entire porous body was filled with an active material mixture made into a paste of a mixture of 85 parts by weight of nickel hydroxide, 10 parts by weight of nickel powder, and 5 parts by weight of cobalt powder, and after drying, the whole was further pressurized. , the overall thickness was set to approximately 0.9 mm. and width 38
It was cut into pieces of mm to obtain a nickel positive electrode approximately 150 mm long and 0.9 mm thick. Electrode leads were attached to this, and a general-purpose cadmium negative electrode and a separator were wound between them to create a AA cylindrical alkaline battery.

In this case, before filling the active material, if you start winding the porous body from the part corresponding to the low porosity part through a separator together with a cadmium pole of the same size as the nickel pole, the small There were few cracks in the winding diameter, and it could be rolled smoothly without breaking. Further, even if the product was turned back in the opposite direction, a small amount of cracks remained, but it did not break and it was possible to swirl it again. However, with conventional electrodes made from porous materials that do not have low-porosity areas before being filled with active material, cracks often develop in the electrodes from the beginning of winding, leading to breakage. Naturally, when it was rewound, it broke and it was impossible to regenerate the electrode.

Next, battery A using nickel electrodes according to the present invention
And regarding battery B using conventional nickel electrodes,
When battery A was repeatedly charged and discharged by charging at 200 mA for 15 hours and discharging at 400 mA, battery A showed a capacity of 2.5 Ah, which was the same as the initial value, even after 50 cycles, but battery B had a capacity of 2.0 Ah after 50 cycles. Capacity decreased to . The cause of this is considered to be a decrease in capacity due to an internal short-circuit phenomenon due to cracks at the winding start of the electrode, falling of the active material due to collapse, and exposure of the skeleton of the porous body.

Note that the compression degree of the portion where the porous body is compressed under pressure before being filled with the active material is preferably about 5 to 50% of the original thickness of the porous body. When it is less than 5%, it has no effect on the minimum diameter of the spiral, and when it is over 50%, it has a very advantageous effect on the minimum diameter of the spiral, but the amount of active material packed in that part decreases. Capacity decreases.

As mentioned above, by pressurizing and compressing the part of the porous body corresponding to the winding start end of the electrode to make it have a low porosity before filling the active material, the amount of active material filled into this part is limited. The amount of active material in the skeleton made of the sponge-like porous metal material is reduced, allowing the skeleton to have more flexibility and reducing stress on the skeleton. Therefore, even when the winding diameter is small,
It can sufficiently withstand the winding strength. Moreover, if the boundary part to be pressurized is provided with an inclination, there will be no cracks from that part, making it more effective.

As described above, according to the present invention, it is possible to prevent a decrease in the life of a spiral electrode using a sponge-like porous metal material due to cracking or breakage, and to obtain an electrode with a long life and high capacity.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the general structure of a sponge-like porous metal material, Fig. 2 is a plan view of a continuous sheet of a sponge-like porous metal material for making a large number of electrodes, and Figs. 3 and 4 are the same. FIG. 5 is a front view showing an example of the electrode according to the present invention, and FIG. 6 is a cross-sectional view of a group of electrode plates that have started to be spirally wound. 1... Lattice, 2... Space, 3... Sponge-like porous sheet, 4... Low porosity part, 5...
Highly porous areas.

Claims (1)

[Claims] 1 In a method for manufacturing an electrode in which a spongy metal porous body having a three-dimensional structure is used as a holder for an active material and the active material is held on this and spirally wound, the porous body corresponding to the winding start end of the electrode is a step of pressurizing the portion to a degree of compression of 5 to 50% of the original thickness of the porous body to make it have a lower porosity than other portions, and then filling the entire porous body with an active material. 1. A method for manufacturing a spiral electrode for a battery, comprising the steps of compressing the entire electrode under pressure to a desired electrode thickness.