JPH04255668A - Hydrogen storage alloy electrode and manufacture thereof - Google Patents

Abstract

PURPOSE:To dissolve problems of a low discharge characteristic and a short life in a hydrogen storage alloy electrode to be used for such as a nickel - hydrogen storage battery in order to provide the hydrogen storage alloy electrode excellent in an initial characteristic and a utilization factor. CONSTITUTION:For instance, ZrMn0.3Cr0.3V0.15Ni1.15 which is one of C 15 type Laves phase alloys is used for hydrogen storage alloy powder and nickel powder composed of nickel salt water solution zinc powder is mixed with or stuck to this hydrogen storage alloy powder in order to manufacture an electrode. When this electrode is made a negative electrode and a known nickel electrode is used for a positive electrode so as to constitute a battery, the battery excellent in an initial characteristic and a utilization factor, and having long life can be obtained.

Description

Description: [0001] The present invention relates to a hydrogen storage alloy electrode used in nickel-hydrogen storage batteries and the like, and a method for manufacturing the same. [0002] Lead storage batteries and alkaline storage batteries are widely used as various power sources. Among these, alkaline storage batteries are expected to have high reliability, and because they can be made smaller and lighter, small batteries have been used for various portable devices, and large batteries have been used for industrial purposes. [0003] In this alkaline storage battery, some air electrodes and silver oxide electrodes have been used as positive electrodes, but
Most often nickel electrodes. The pocket type was replaced by the sintered type, which improved its properties, made it possible to seal it more tightly, and expanded its uses. On the other hand, in addition to cadmium, zinc,
Targets include iron and hydrogen. Recently, nickel-hydrogen storage batteries using metal hydrides, that is, hydrogen storage alloy electrodes, have attracted attention in order to achieve even higher energy density, and many proposals have been made for manufacturing methods. For example, in order to particularly improve the oxidation resistance, utilization rate, and moldability of hydrogen-absorbing alloy powder, a technique is known in which the particle surface is plated with nickel or copper to form a porous metal layer. Additionally, processes such as heat treatment in a vacuum or immersion in an alkaline solution after manufacturing the alloy have been proposed in order to improve its properties. Furthermore, when applied to a closed type, attempts have been made to add fluororesins and catalysts to improve the absorption of oxygen gas from the positive electrode during charging and hydrogen gas that may be generated during overcharging. There is. [0007] Hydrogen storage alloy electrodes can be manufactured by sintering alloy powder or by filling or coating alloy powder into a porous support such as foamed, fibrous or punched metal. There is a strike style, etc. Among these, the paste method is the easiest to manufacture. Hydrogen storage alloys, like cadmium electrodes and zinc electrodes, have relatively good electronic conductivity, so there is great potential for non-sintered electrodes. That is, it is generally made into a paste together with a binder and filled or applied to a porous conductive plate having a three-dimensional or two-dimensional structure. [Problems to be Solved by the Invention] However, the conventional configuration described above requires improvement in terms of improving the discharge characteristics at the beginning of the charge/discharge cycle, further improving the utilization rate, and improving the high rate discharge characteristics. Ta. In addition, the sealed type can basically be used because it is possible to absorb the generated gas at the negative electrode like the nickel-cadmium type, but there is a problem that the rapid charging performance must be further improved. [0009] The present invention solves the above problems,
The purpose of the present invention is to provide a hydrogen storage alloy electrode with excellent initial properties and utilization rate, and a long life, and a method for manufacturing the same. [Means for Solving the Problems] In order to achieve the above object, the present invention provides an electrode material in which active nickel powder synthesized from a nickel salt aqueous solution and zinc powder is mixed or adhered to hydrogen storage alloy powder. It is composed of [Operation] Therefore, according to the present invention, since the electrode material is formed by mixing or adhering nickel powder synthesized from a nickel salt aqueous solution and zinc powder to the hydrogen storage alloy powder, the electrode material is It is extremely active, and therefore the acceleration of hydrogen storage into the hydrogen storage alloy during charging is extremely large. [Embodiment] A hydrogen storage alloy electrode according to an embodiment of the present invention will be explained in detail below. (Example 1) Lave as a hydrogen storage alloy
ZrM based on ZrMn2, which is one of the s-phase alloys
A powder obtained by crushing n0.3Cr0.3V0.15Ni1.25 and passing it through 400 mesh was used. Active nickel powder was synthesized as follows. A hot aqueous solution of nickel chloride was added all at once while stirring to an aqueous solution in which fine zinc particles were dispersed in a small amount of water to precipitate nickel powder. The precipitated nickel powder was washed with water, treated with a 10% by weight aqueous solution of caustic soda at 55° C. for 20 minutes, and washed again with water to synthesize active nickel powder. [0015] 10% by weight of the synthesized active nickel powder was added to the above hydrogen storage alloy powder and mixed using a ball mill to prepare an electrode material powder. Add a styrene resin rubber aqueous dispersion liquid to this electrode material powder until the resin reaches 0.
A paste was prepared by adding 5% by weight. This paste was filled into a foamed nickel plate with a porosity of 95% and a thickness of 0.8 mm, and after drying under reduced pressure, a 5% fluororesin dispersion liquid was applied to the surface, and the plate was cut into a predetermined size. Then, an electrode was created by attaching a lead plate by spot welding. This electrode will be referred to as electrode A. Next, as a comparative example, an electrode was prepared in the same manner as Electrode A using an electrode material powder not mixed with the synthesized active nickel powder. This electrode will be referred to as electrode B. First, in order to investigate the characteristics of both as negative electrodes, a sintered nickel electrode with a sufficiently large capacity to meet the negative electrode rule was used as the counter electrode, and a specific gravity of 1.30 was used as the electrolyte.
The test was conducted using an aqueous solution of caustic potassium in an open type with a rich electrolyte. When constant current charging to 140% of the negative electrode capacity was performed at a rate of 5 hours - constant current discharging at 0.5 A to 0.9 V, the discharge capacity density of electrode A was 270 mAh in one cycle.
/g, 290mAh/g after 2 cycles, and remained almost constant at 310mAh/g after 3rd cycle. However, electrode B
So, 25mAh/g in 1 cycle and 30mAh/g in 2 cycles.
mAh/g was 75mAh/g for 3 cycles and became almost constant after 10 cycles, but the capacity density was 270mAh/g.
It was g. This result shows that electrode A has improved cycle initial characteristics and a high utilization rate. Next, a sealed nickel-metal hydride storage battery according to the positive electrode rule was constructed in the conventional manner. A well-known foamed nickel electrode was used as the counter electrode, and a hydrophilically treated polypropylene nonwoven fabric was used as the separator. The electrolytic solution used was one in which 25 g/l of lithium hydroxide was dissolved in a caustic potassium aqueous solution with a specific gravity of 1.25. The batteries were AA type. The capacity of the negative electrode relative to the positive electrode is 15
It was set to 0%. Battery A was a battery using electrode A made from a mixture of active nickel powder synthesized from an aqueous nickel salt solution and zinc powder. Next, a battery using electrode B of a comparative example was designated as battery B. Since the same weight of alloy was used, the capacity of the negative electrode relative to the positive electrode was approximately 140%. First, the initial discharge voltage and capacity were compared. 5
130% constant current charging of capacity at time rate - 0.9 at 1.0A
When constant current discharge was performed up to V, the average voltage of battery A was 1.24 V, and the discharge capacity was approximately constant from 2 cycles to 2.7 to 2.9 Ah. However, in battery B, the average voltage was 1.21 V, and it took 30 cycles for the discharge characteristics to improve and become almost constant. [0022] Next, 10 each of battery A and battery B
The life characteristics of the cells were compared under these charging and discharging conditions. As a result, at 500 cycles, the discharge capacity in all cases was maintained at 95% or higher under the positive electrode rule, but at 750 cycles, battery A still showed the initial 87% under the positive electrode rule. In battery B, the negative electrode rule was applied and the ratio was 74%. As is clear from these results, it can be seen that battery A has an extremely long life. (Example 2) Zr as hydrogen storage alloy powder
Mn0.3Cr0.3V0.15Ni1.25 was used. Hydrogen storage alloy ZrMn0.3Cr0.3V
10% by weight of zinc 400 mesh powder was added to 100-400 mesh powder of 0.15Ni1.25 and ground in a mortar to adhere zinc to the hydrogen storage alloy to create a 400 mesh passing powder. This powder was dispersed in a small amount of water, and a hot aqueous solution of nickel chloride was added all at once while stirring at 80°C.
It was treated for 1 hour. After washing this powder with water, it was treated with a 10% by weight aqueous solution of caustic soda at 55° C. for 20 minutes, and washed again with water to synthesize an electrode material powder. An electrode was prepared using this electrode material powder in the same manner as in Example 1, and its properties as a negative electrode were investigated. As in Example 1, the test method was to use a sintered nickel electrode as a counter electrode with a sufficiently large capacity to satisfy the negative electrode rule, and a caustic potassium aqueous solution with a specific gravity of 1.30 as an electrolyte. Tests were conducted in an open configuration with plenty of liquid. When constant current charging to 130% of the negative electrode capacity was carried out at a rate of 5 hours - constant current discharging at 0.5 A to 0.9 V, the discharge capacity density of electrode A was 260 mAh in one cycle.
/g, 285 mAh/g after 2 cycles, and remained almost constant at 305 mAh/g after 3 cycles. Next, a sealed nickel-metal hydride storage battery using the positive electrode rule was constructed in the conventional manner. A well-known foamed nickel electrode was used as the counter electrode, and a hydrophilically treated polypropylene nonwoven fabric was used as the separator. The electrolytic solution used was one in which 25 g/l of lithium hydroxide was dissolved in a caustic potassium aqueous solution with a specific gravity of 1.25. The batteries were AA type. The capacity of the negative electrode to the positive electrode is 14
It was set to 0%. Constant current charging at 130% capacity at a 5 hour rate-1
．． When constant current discharge was performed to 0.9V at 0A,
The average voltage of the battery was 1.24 V, and the discharge capacity remained almost constant after 2 cycles, ranging from 2.7 to 2.9 Ah. Next, the life characteristics were investigated under these charging and discharging conditions. As a result, the discharge capacity maintained 95% or more of the initial discharge capacity under the positive electrode rule at 500 cycles, and 86% of the initial discharge capacity under the positive electrode rule at 750 cycles. From this result, it was confirmed that the battery according to this example had a long life. [0030] The hydrogen storage alloy powder is AB2 type Lav.
Although this is the case for es-phase alloys, equally excellent results can be obtained with LaNi5-based alloys. Further, in the examples, a caustic soda aqueous solution was used as the treatment liquid, but the same effect can be obtained by treating with an acetic acid aqueous solution. Furthermore, although a ball mill and a mortar were used for mixing, zinc particles synthesized from a high-speed air impact method, or nickel particles synthesized from a zinc and nickel salt aqueous solution, or zinc adhered to a hydrogen storage alloy by plating, could be similarly mixed. I was able to obtain the effect of As described above, according to the above embodiment, since the electrode is formed by mixing active nickel powder with hydrogen storage alloy powder, a battery using this hydrogen storage alloy electrode has excellent initial characteristics and It has the advantage of extremely long life. [Effects of the Invention] As is clear from the above examples, the hydrogen storage alloy electrode of the present invention can improve the initial characteristics and the utilization rate, and can extend the life of the hydrogen storage alloy electrode. can be used to provide extremely high performance batteries.

Claims (3)

[Claims] 1. A hydrogen storage alloy electrode comprising an electrode material in which nickel powder synthesized from a nickel salt aqueous solution and zinc powder is mixed or adhered to hydrogen storage alloy powder. Claim 2: The general formula of the hydrogen storage alloy powder is ABα (α=
1.5 to 2.5), the alloy phase substantially belongs to the Laves phase of an intermetallic compound, and the crystal structure is a hexagonally symmetrical C14 type or a cubic symmetrical C15 type. The hydrogen storage alloy electrode according to claim 1. 3. Manufacture of a hydrogen storage alloy electrode characterized in that the electrode is formed by mixing or adhering zinc to hydrogen storage alloy powder and then immersing it in an aqueous nickel salt solution to mix or adhere nickel powder. Law.