JPS58198859A - Positive plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To obtain a positive plate for an alkaline storage battery which has an increased volume energy density by optimumly adjusting the relationship between the grain diameter of an active material and the amount of graphite. CONSTITUTION:A positive plate for an alkaline storage battery is made by mixing 100pts.wt. of an active material with 8-20pts.wt. of graphite. Here, the grain diameter y (mu) of the active material and the amount x (wt%) of graphite used are restricted so that they satisfy the relationship represented by the equation of -(1/8)x+6.5>y>-(1/8)x+5.5. Thus, when the grain diameter of the active material and the amount of graphite used are restricted to within the above range, a positive plate with a high volume energy density can be obtained.

Description

[Detailed Description of the Invention] This invention relates to an anode plate for alkaline storage batteries.The purpose of this invention is to create an anode with high volumetric energy density by optimizing the particle size of active material such as nickel hydroxide and the amount of graphite. The purpose is to provide a board.

Conventional alkaline storage battery 1 For example, the method for manufacturing the anode plate of a nickel-cadmium storage battery is to make a sintered substrate using carbonyl nickel powder or the like.

The sintering type holds the active material in it, and the pocket type involves mixing an active material such as nickel hydroxide with a conductive agent such as graphite and inserting the mixture into a porous metal pocket.

There is a paste method in which a conductive agent and a binder such as a fluororesin are added to the active material and applied onto a substrate such as a nickel mesh.
Among these, the sintering type has excellent characteristics such as cycle life and utilization rate, but is expensive because the manufacturing process is complicated.

On the other hand, the pocket type is a relatively inexpensive manufacturing method, but is inferior in terms of high rate discharge and utilization rate. On the other hand, the paste method allows for continuous production and is inexpensive. However, the plate characteristics are inferior to the sintered type in terms of low utilization rate and short cycle life. Various methods have been considered to improve these drawbacks. For example, as a method of improving the utilization rate, there is a method of using a core with a large surface area and using a conductive agent such as graphite in multiple needles.

Furthermore, in order to improve the cycle life, there is a method of increasing the amount of binder added to prevent the active material from falling off. However, no matter which of these methods is used, the second disadvantage is that the amount of active material per unit weight and unit volume decreases, resulting in a decrease in energy density.

As a result of various experiments conducted to improve this drawback, it was found that there is a relationship between the particle size of the active material and the amount of graphite. In other words, it was found that when a specific amount of graphite is used for nickel hydroxide of a specific particle size, an anode plate with a high volumetric energy density can be obtained.

According to this invention, when graphite is in the range of 8 to 20 parts by weight with respect to 100 parts by weight of the active material, the linear formula [where X represents the amount of graphite (coulometric %) and y represents the particle size (μ) of the active material] ] Provided is an anode plate for an alkaline storage battery, characterized in that it is manufactured using an active material having a particle size within the following range and an amount of graphite.

The active material in this invention means an active material for an anode of an alkaline storage battery, and examples thereof include nickel hydroxide, silver oxide, and the like. Also.

In the production of the anode plate for an alkaline storage battery of the present invention, there are no particular limitations on the method used and other materials other than those that are characteristic of the present invention, and those known in the field may be used as appropriate.

Next, this invention will be explained including experimental results.

Using various particle sizes of nickel hydroxide as the active material,
On the other hand, Table 1 shows the results when the amount of graphite was changed.

8-4- The measurements shown in Table 1 were performed by wrapping one anode plate and two cathode plates with a separator in between, placing them in a plastic bag, and pressurizing them with a plastic plate. The electrolyte is KOH1 component (SG 1.2
8) in a rich liquid state.

Charging is the theoretical capacity of the electrode plate, O, xCX16hr, discharging is 0,
I did it with IC.

Note 2) Particle size is the average particle size measured with a subsieve sizer.

Since the filling factor shown here indicates the amount of nickel hydroxide contained per unit volume of the electrode plate, it is desirable that the filling factor be larger in order to obtain an electrode plate with a higher volumetric energy density.

However, as can be seen from this result, the conditions that are most important for filling and the conditions that are most important for utilization do not match, and it is necessary to find a composition that meets the optimal conditions in order to obtain a high volumetric energy density.

In addition, the larger the amount of graphite, the higher the filling rate, and it seems that graphite also functions as a lubricant when added at least to this extent. Next, FIG. 1 shows the relationship between the volumetric energy density, the particle size of nickel hydroxide, and the amount of graphite.

As can be seen from FIG. 1, the volume energy density is maximum when the particle size of nickel hydroxide is 4μ or 5μ. In addition, when the particle size is 8 μm or less, a utilization rate equivalent to that of 4 to 5 μm can be obtained, but the filling rate becomes low and the volumetric energy density becomes low, which is unsuitable.

By the way, when comparing electrode plates with the same amount of graphite, it can be considered that the one with the largest filling factor x utilization factor has the largest volumetric energy density. FIG. 2 shows the conditions under which the volumetric energy density obtained from this consideration is maximized.

Usually, the amount of graphite used in a paste type is 8 parts by weight or more, which causes an unpleasant effect, and it is not desirable to add 20 parts by weight or more of graphite from the viewpoint of volumetric energy density.

From FIG. 2, it seems that the conditions for providing a high volumetric energy density when the amount of phytophyte is in the range of 8 to 20 parts by weight are given by the following equation.

X: Graphite amount (parts by weight) y: Active material particle size (μ) The present invention will be described in more detail below with reference to Examples and Comparative Examples.

Example 1 Weigh out 100 parts by weight of nickel hydroxide (1 particle size: 5μ), 12 parts by weight of graphite, 2 parts by weight of PTFE (using a suspension of polytetrafluoroethylene), and 48 parts by weight of water to make a paste, It was applied onto a mesh and rolled and pressed through a roller to produce an electrode plate. The characteristics of the electrode plate are filling rate: 2, 469fic, utilization rate: ? 2%, volumetric energy density: 401 mAH/cc Comparative Example 1 100 parts by weight of nickel hydroxide (1 particle size: 19μ).

Graphai) 1 j? , weight part, PTFE! weight part,
48 parts by weight of water was weighed to form a paste, which was applied onto a nickel mesh, and rolled and pressed through rollers to produce an electrode plate. Its plate characteristics are: filling rate: 2.47f/cc, utilization rate: 68cm, volumetric energy density: 822mAfl/
Ce Comparative Example 2 Weighed 100 parts by weight of nickel hydroxide (1 particle size: 4μ), 28 parts by weight of graphite, 2 parts by weight of PTFE, and 48 parts by weight of water to make a paste, applied it on a nickel mesh, and rolled it through a roller. An electrode plate was prepared by pressing. The characteristics of this electrode plate are: filling rate: 2.80f/ac utilization rate = 79cm, volumetric energy density 820mAl(/CC

[Brief explanation of the drawing]

FIG. 1 is a graph showing changes in volumetric efficiency when the amount of graphite and the particle size of the active material are changed. FIG. 2 is a graph showing the correlation between the amount of graphite and the particle size of the active material in the anode plate for an alkaline storage battery according to Jin's invention. 7゛Furaceae 11 (Chapter I 4) Part 1! ! 2'1 Figure 2

Claims (1)

[Claims] L graphite is 8 to 20 parts by weight based on 100 parts by weight of the active material.
Manufactured using an active material with a particle size within the range of parts by weight and an amount of graphite according to the linear formula [where X represents the amount of graphite (wt%) and y represents the particle size (b) of the active material]. An anode plate for alkaline storage batteries characterized by: