JPH06275261A - Alkaline storage battery - Google Patents

Abstract

PURPOSE:To electrically connect an active material and a core material, suppress the unnecessary absorption of an electrolyte, improve the performance of a nickel electrode, and extend the life by forming a carbon fine powder layer on the surface of the nickel electrode, and forming a water-repellent resin layer on it. CONSTITUTION:An active material 2 mainly made of nickel hydride and a binder are stuck to a porous conducting core material 1 into a sheet shape to form a nickel electrode. A carbon fine powder layer 3 is formed on the surface of the nickel electrode, a water-repellent resin layer 4 is formed on it to manufacture a paste type nickel electrode. The active material 2 and the core material 1 can be electrically connected, the resistance at the time of charge/discharge is reduced, the unnecessary absorption of an electrolyte is suppressed by the water-repellent resin layer 4, the performance as the nickel electrode for an alkaline storage battery is improved, the expansion or fallout of the active material 2 is suppressed, and the performance can be maintained for a long period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline storage battery such as a nickel-cadmium battery, a nickel-zinc battery or a nickel-hydrogen battery using a paste type nickel electrode for a battery.

[0002]

2. Description of the Related Art In recent years, alkaline storage batteries used as various power sources are expected to have high reliability and can be made compact and lightweight. For this reason, small batteries have been widely used for various portable devices, and large batteries have been widely used as industry. There is.

The conventional alkaline storage battery and its manufacturing method will be described below. In this alkaline storage battery, zinc, iron, hydrogen, etc. are targeted as the negative electrode in addition to cadmium. On the other hand, as the positive electrode, an air electrode, a silver oxide electrode, and the like are partially taken up, but in most cases, it is a nickel electrode. Then, instead of the pocket type instead of the sintering type, the utilization rate of the active material is improved, high discharge is possible, and long life is secured. In addition, it has become possible to make it airtight and its applications are expanding.

However, the sintering method is complicated and expensive in terms of a method of manufacturing a substrate and filling of an active material. When the porosity of the substrate is 85% or more, the strength is significantly reduced, so that there is a limit to the filling of the active material, and thus there is a limit to the increase in capacity. Therefore, in order to increase the capacity, a substrate having a high porosity of 90% or more, that is, a foamed substrate or a fibrous substrate as a core material is taken up and put into practical use instead of the sintered substrate.

Another problem of the sintered nickel electrode is cost reduction. In this case, a punching metal, an expanded metal, a screen or the like is used as a core material, and nickel hydroxide is used as a conductive material and nickel, graphite, activated carbon or carbon black is used as a conductive material. Etc. and a binder such as carboxymethyl cellulose, polyvinyl alcohol, fluorocarbon resin, rubber resin, etc. are added and a non-sintered type obtained by processing into a sheet shape together with a porous body with a two-dimensional structure has been widely studied and used in many manufacturing methods. Has been proposed. The non-sintered type obtained by adding a binder such as graphite and carboxymethyl cellulose to nickel hydroxide using punching metal as the core material is less expensive than the sintered type.

[0006]

However, nickel hydroxide, which is the active material of the nickel electrode, has almost no electronic conductivity in both charging and discharging states, and the electrode tends to swell due to repeated charging and discharging. . Therefore, it is preferable that the active material be held in the fine pores made of conductive nickel as in the sintering method. That is, it is advantageous in terms of electrical conductivity and can suppress expansion. However, in the non-sintered type, the core material having a two-dimensional structure such as punching metal does not have such three-dimensional holes, and therefore it is further disadvantageous in terms of electrical conductivity and expansion suppression.

Therefore, in these cases, nickel, graphite, activated carbon, carbon black or the like is added as a conductive material to the powder of nickel hydroxide or nickel oxyhydroxide used as the active material. However, if the added amount is small, the effect can hardly be expected, and if the added amount is too large, the absolute amount of the active material decreases.

Alkali-resistant resins are preferable for suppressing the expansion and drop-off of the active material, but both fluororesins and rubber-based resins have water repellency and insulation properties, so that the initial charging efficiency is low, especially for chemical conversion. It takes a long time.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide an alkaline storage battery which is inexpensive, the absolute amount of the active material is not small, and the expansion and the fall of the active material are suppressed.

[0010]

In order to achieve this object, the alkaline storage battery of the present invention has a porous conductive core material to which a material consisting of an active material mixture mainly containing nickel hydroxide and a binder is attached. It is characterized in that a paste type nickel electrode is used in which a fine carbon powder layer is formed on the surface of a nickel electrode formed into a sheet and a water repellent resin layer is formed on the fine carbon powder layer. This paste-type nickel electrode uses a mixture of active materials mainly containing nickel hydroxide and a binder selected from carboxymethyl cellulose, polyvinyl alcohol, fluororesin, rubber resin, etc. , A fine carbon powder layer such as graphite is formed on the surface of the nickel electrode obtained by adhering it to a porous conductive core material selected from punching metal, expanded metal, screen, etc. And a water-repellent resin layer such as

[0011]

With this structure, in a punching metal, expanded metal, screen, etc. having a two-dimensional structure, a layer of fine carbon powder is formed on the surface of the electrode to electrically connect the active material and the core material. This makes it possible to wrap the active material in a conductive layer such as a sintered body with a small amount of addition. Since the carbon fine powder layer is porous and the amount thereof may be small, it does not become a resistance during charging / discharging to reduce the voltage, but rather serves as a conductive layer for reducing the resistance.
Further, by forming a water-repellent resin layer such as a fluororesin on the layer of carbon fine powder to make it water-repellent, unnecessary absorption of the electrolytic solution is suppressed, and the life can be extended.

[0012]

The present invention will be described in detail below. Figure 1
1 shows a nickel electrode of an alkaline storage battery according to an embodiment of the present invention, where 1 is a porous conductive core material, 2 is an active material layer mainly containing nickel hydroxide, 3 is a carbon fine powder layer, and 4 is a repellant. It is an aqueous resin.

75 parts of commercially available nickel hydroxide powder, 6 parts of cobalt powder, 5 parts of graphite as a conductor, 10 parts of nickel powder, and acrylonitrile single fiber 0.8 as a reinforcing agent.
To this, a 4% by weight aqueous dispersion solution of a commercially available rubber-based resin is added so that the amount of this resin is 3.5 parts with respect to nickel hydroxide to form a paste. This paste was applied to an iron-made nickel-plated punching metal plate having a thickness of 0.17 mm, a hole diameter of 1.8 mm, and an opening degree of 53%, and smoothed through a slit having a gap of 0.4 mm. Then, it was dried at 100 ° C. for 1 hour.

The paste type nickel electrode thus obtained was cut into a width of 33 mm and a length of 200 mm, and a lead plate was attached by spot welding. The actual discharge capacity of this nickel electrode is 2.3 Ah at 0.2 C. afterwards,
0.5% of commercially available graphite powder carboxymethyl cellulose
An amount of about 3 mg of graphite per 1 cm ^{2 of} the electrode was applied using the suspension added by weight% and then dried. Finally commercially available poly 4
An 8 wt% dispersion aqueous solution of fluorinated ethylene was added and then dried.

As a counter electrode, a known paste type cadmium electrode and a polyamide non-woven fabric separator were used to construct a sealed nickel-cadmium battery. As an electrolytic solution, 25 g / 1 of lithium hydroxide was dissolved in a caustic potash aqueous solution having a specific gravity of 1.25 and used. The battery is a SubC type. This battery is designated as A.

Next, for comparison, only the graphite layer was formed without adding the fluororesin, and the battery obtained by the same process as A was otherwise added as B.

Each of the two batteries has a capacity of 300 m using 10 cells each.
A was charged for 15 hours, and the formation of discharge at 300 mA to 0.8 V was repeated 3 times to form a formation. As a result, A,
The capacity of both B was 2.25 to 2.35 Ah.

After the formation was completed, a cycle test was conducted in which a constant current charge of 115% of the capacity was carried out at 0.5C and a discharge up to 0.9V was carried out at 0.7C. As a result, in 300 cycles, A
The average capacity was 2.19 Ah, while that of B was 1.77 Ah. At 500 cycles, the average capacity was 2.02 Ah in A, but 1.6 in B.
It was 3 Ah.

[0019]

As described above, according to the present invention, the surface of a nickel electrode obtained by forming a sheet together with a porous conductive core material using a binder in an active material mixture mainly containing nickel hydroxide is formed. By forming a fine carbon powder layer such as graphite and a water repellent resin layer on the fine carbon powder layer, the cost is low, the absolute amount of the active material is not small, and the expansion and dropping of the active material are suppressed, and the performance is improved. It is possible to provide an alkaline storage battery that can be maintained for a long time.

[Brief description of drawings]

FIG. 1 is a sectional view showing a nickel electrode of an alkaline storage battery according to an embodiment of the present invention.

[Explanation of symbols]

 1 Porous Conductive Core Material 2 Active Material Layer 3 Carbon Fine Powder Layer 4 Water Repellent Resin Layer

Front page continuation (72) Inventor Yoichiro Tsuji 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Naoko Maekawa, 1006 Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A carbon fine powder layer is formed on the surface of a nickel electrode formed by adhering a material comprising an active material mixture mainly containing nickel hydroxide and a binder to a porous conductive core material to form a sheet. An alkaline storage battery in which a water-repellent resin layer is formed on the carbon fine powder layer. 2. The alkaline storage battery according to claim 1, wherein the fine carbon powder layer is made of graphite. 3. The binding material is carboxymethyl cellulose,
The alkaline storage battery according to claim 1, which is selected from polyvinyl alcohol, fluororesin, rubber-based resin, and the like. 4. The porous conductive core material is foam-like, fiber cloth-like,
The alkaline storage battery according to claim 1, which is selected from punching metal, expanded metal, screen and the like.