JPS59163762A - Positive plate for alkaline battery - Google Patents

Abstract

PURPOSE:To improve the performance of a positive plate, in which a three- dimensionally-continuous porous spongy nickel body, a nickel net or the like is used as a supporter, remarkably by adding as an additive a small amount of cobalt powder obtained through partial sintering and having a continuous chain- like structure to make the positive plate. CONSTITUTION:An active material powder principally consisting of nickel hydroxide powder and a cobalt powder which is obtained through partial sintering and has a chain-like structure, is packed into an active-materal-holding body. The active-material-holding body consists of either a member enwrapped in a nickel net or a porous spongy nickel body having a three-dimensionally continuous structure for example. As to a method for the above partial sintering of cobalt powder, it is heated to 300-450 deg.C for example. In addition it is preferred that the mean grain diameter and the mean grain length of cobalt powder having chain-like structure be respectively 1-5mu and 5-30mu and that its content be 2-10wt% of the active material powder.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a 1F electrode plate for an alkaline battery using a three-dimensional continuous nickel porous material, nickel mesh, etc. as a support, and as an additive. By adding a small amount of cobalt powder to the continuous silane structure obtained by partially sintering, it was discovered that the triability of the electrode plate could be significantly increased. It is something.

Conventionally, a sintered body of Nienokel powder has been used as a substrate for the positive electrode plate of alkaline batteries, but its porosity is 70%.
It is about ~80%, and if the porosity is increased beyond this, the mechanical strength will be significantly reduced, and if the positive FM active material is filled into the void, the substrate will be There were drawbacks such as deformation, cracking, and peeling of the active material. First, when filling the active material, the method is usually called Wi-field impregnation method, that is, the substrate is impregnated under reduced pressure with an aqueous solution of nickel salt such as nickel nitrate or nickel sulfate, and then treated with an alkaline aqueous solution. The method of repeating the operation of washing with hot water and drying is 61%, however, the number of sprays filled by the -times is small, and the amount filled gradually decreases from the second time, so it is usually 4 times. It is necessary to repeat the operation ~IO times. This has the disadvantage that the manufacturing process is complicated and the economic cost is high.

Therefore, in recent years, positive rM7i! has been applied to a sponge-like porous body made of dikel metal with a three-dimensionally continuous structure in the form of a paste. The method of directly filling materials has been attracting attention because of its three-dimensionally continuous structure.Subnononal nickel porous materials have a high porosity of 90 to 98% and are easy to machine. The strength is great. Moreover, since the pore size is large, it is possible to fill the active material into this porous body and achieve a high net content of the positive electrode plate.The filling method can be extremely shortened to 1m, making it possible to perform a continuous process, which is economically advantageous. However, since the porous material has large areas, sufficient electrical contact between the Nykel porous material, which is the current collector, and the active material powder and between the active material particles cannot be obtained, resulting in a low utilization rate. It has the disadvantage of being low. Therefore, attempts have been made to improve the utilization rate by adding 2 to 2 liters of conductive material and various additives. It has been suggested that cobalt powder should be used as this additive.

It is known that the particle shape of cobalt powder varies greatly depending on the manufacturing method, and attempts have been made to improve the utilization rate by using cobalt powder with different particle shapes. However, the effect of light cannot be obtained. The mechanism behind this effect is that during charging, cobalt forms an oxide that increases oxygen generation overvoltage, and hydroxide (which improves the photoelectric efficiency of the positive electrode plate and enters the lattice of nickel hydroxide) It is generally said that , increases the lattice spacing and facilitates photodischarge, but the basis for this is not clear.

The present invention is based on the discovery that when cobalt fine powder is partially sintered to form a continuous chain structure as an additive, the efficiency of the electrode plate can be significantly improved. be.

Examples of the present invention and its effects will be described in detail below.

A continuous chain-like t-14 structure due to uninventiveness can be manufactured in the following manner at any age. For example, a cobalt powder with an average particle size of 1.4 microns obtained by reducing oxalic acid with hydrogen can be used to produce a loose sinter set of two carbon plates, etc. The fine cobalt powders may be partially sintered by heating in a reduced atmosphere such as hydrogen, an inert atmosphere such as a gas filled in a container, or in a vacuum. In this case, if the heating temperature is below 300"C, sintering between particles will not proceed sufficiently and a chain structure will not be formed, and if the heating temperature is above 450"C, kidney sintering will occur. The cobalt powder bed obtained by sintering at a temperature of 300 to 450"C has an average particle size of 1 to 5μ and an average particle length of 5.
What do you do with a ~30μ chain structure? Cobalt powders having similar chain structures were obtained even when the cobalt fine powders were produced using different methods.

Next, in order to examine the effects of the present invention, a positive electrode plate was manufactured using the obtained cobalt powder as described above. First, the conomalt powder bed obtained by sintering at 400℃ is diluted with hydroxide.
A carboxymethyl cellulose solution of Q, (iwt%) was added to the powder and made into a paste. [Continuing the process, the structure was filled into a porous nickel material and dried, then immersed in a dispersion of fugitive resin and dried again to a thickness of 068 mm. Then, a positive electrode plate (N) according to the present invention was obtained. In this way, a conventional positive electrode plate (also manufactured by Hitoshi) using fine cobalt powder that was not sintered for the sake of contrast. H, G due to one positive electrode plate, two sintered negative electrode plates, and electrolysis.1.
250 (2oC) Potassium hydroxide aqueous solution was used.
After heating for 20 hours at
Ko. Figure 1 shows the changes in the active material utilization rate when the amount of cobalt powder added was changed. From the figure, it can be seen that when the cobalt powder according to the present invention is used, the utilization rate is significantly improved when the amount of cobalt added is about 2%, and when the amount of cobalt added is 10%, the utilization rate reaches 100%. Further, FIG. 2 shows the changes in the discharge midpoint potential of the positive electrode plate when the amount of cobalt added Il+ and the discharge rate were changed. It can be seen from the figure that the discharge intermediate potential increases as the amount of cobalt added increases. M1
Comparing the case according to the present invention and the case of the conventional method, it can be seen that the decrease in the discharge IEt level when the discharge rate increases is smaller in the case of the present invention. After examining the electrode plates used in these experiments, we found that the electrode plates with a high utilization rate were harder and less likely to shed the active material. Let's take a look at the effect of the length. First, the chain structure obtained by sintering at 400°C is pulverized using a ball mill to obtain 5 wt of cobalt powder for the entire active material. % was used to produce a positive electrode plate. FIG. 3 shows the relationship between grinding time and active material utilization rate.

From the figure, the longer the grinding time, the lower the utilization rate.
Karu. Here, it has been confirmed by electron microscopy that the longer the grinding time, the shorter the average particle length of the powder. Also,
FIG. 4 shows the relationship between the pulverization time and the discharge midpoint potential of the positive electrode plate. From the figure, the longer the grinding time, the longer the particle length force 5
From the above results, the effect is greater when using cobalt powder as particles with a long chain structure than when using it as a single fine particle. ) koto power; wa power) ro.

This neglects the fact that cobalt has an extremely important role as a conductive material.

The effect will be explained in detail below. In other words, the powder bed is easily oxidized during charging, unlike the powder bed.
．． It changes to KW cobalt and further to ihibalt oxyhydroxide. This oxyhydroxide cono (root “) 1 lead￥
It has a high conductivity, and the conductivity of nickel hydroxide and nickel hydroxide is several Ω compared to 0 Ω.
It has a relatively high conductivity of about −1·α−1. Well, nickel oxyhydroxide is reduced and changed to dikel hydroxide, but cobalt oxyhydroxide is hardly reduced. Therefore, even after repeated charging and discharging cycles, cobalt 0-oxyhydroxide, which has high conductivity and is not reduced, is always present, and the conductivity inside the electrode plate is maintained well. Bankokonoru I ~ It is thought that increasing the amount of powder added reduces the drop in discharge potential and improves the utilization rate. In the case of C, fine particles exist alone as in the conventional case. Then, contact between particles II! However, if a powder bed with a continuous chain structure is used, there will be a long conductive path; It is thought that because a transparent network structure is formed within the electrode plate, a significant effect can be obtained even with the addition of 9 ml. First, once the network structure is formed firmly, the active material is strongly held, the electrode plate hardens, and the active material 6 is likely to fall off, resulting in a decline in the number of workers. According to the present invention, by partially sintering cobalt powder as an additive to obtain a continuous chain structure, the performance of the positive electrode plate can be improved by adding a small amount of cobalt powder. Be able to make a significant difference. In addition, in the detailed explanation of the present invention, a three-dimensional sponge-like porous material is used as an example of an active material support, and the active material is wrapped in a 2-layer mesh or the like. Needless to say, similar effects can be observed even when using

[Brief explanation of the drawing]

Figures 1 and 2 show the changes in the active material utilization rate and discharge midpoint when the amount of conomalt added is changed, and Figures 3 and 4 show the changes in cobalt powder. Figure 13 shows the changes in the utilization rate of active materials and the discharge midpoint potential when the grinding time is increased.奔 １ Zudon Z Picture Conor ＼＼＼ＺＺ (鈱ＺＺＺ) ｜ﾔﾔ＾Ｚｲ＾＾

Claims (1)

[Claims] 1. Obtained by partially sintering 1tZ hydroxide nickel powder.
This chain-like structure is formed by wrapping the cobalt powder in an active material support, such as a nickel mesh, or by wrapping the cobalt powder in an active material support, or by using a sponge-like needle porous structure having a three-dimensionally continuous structure. A positive electrode plate for an alkaline battery, which is characterized by being filled into a body, etc. 2. The means for sintering the cobalt powder into the partial ribs 9,
A positive electrode plate for an alkaline battery according to claim 1, wherein cobalt powder is heated to 300 to 450"C and sintered. 8. What is the average particle diameter of the cobalt powder forming the continuous chain structure? The alkali 'rlt/l according to claim 1, which has an average particle length of 1 to 5 microns and an average particle length of 5 to 30 microns.
Positive electrode plate for iI. 4. What is the continuous I7 chain structure in the F5 material powder?
fF jθ-calculated / Yakusei distance Ichi pole plate for the alkali turtle Iya described in item 1.