JPH06124704A - Manufacture of hydrogen storage alloy electrode and hydrogen storage alloy electrode - Google Patents

Abstract

PURPOSE:To provide a method for manufacturing a hydrogen storage alloy electrode of large capacity and high activity, and such a hydrogen storage alloy electrode incorporating a larger alloy utilization factor, and an improvement in terms of initial charge and discharge characteristics, lifetime characteristic or charge and discharge characteristics at a high rate. CONSTITUTION:As one of examples, the powder of hydrogen storage alloy as one of C15 type Laves phase alloys and expressed as ZrMn0.5V0.2Co0.1Ni1.2, is formed on an electrode, and the surface of the electrode is plated with an alloy of nickel and tin. This electrode is used as a negative electrode and a publicly known nickel oxide electrode is used as a positive electrode, thereby constituting a battery. According to this construction, initial charge and discharge characteristics are enhanced and a battery can be provided, while ensuring large capacity, long lifetime, and quick charge and discharge capability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a hydrogen storage alloy electrode used as a negative electrode of an alkaline storage battery such as a nickel-hydrogen storage battery, and a hydrogen storage alloy electrode.

[0002]

2. Description of the Related Art Conventionally, there are lead storage batteries and alkaline storage batteries as storage batteries widely used as various power sources. Among them, the alkaline storage battery can be expected to have high reliability and can be made small and lightweight. For this reason, the small battery has been used for various portable devices and the large battery has been used for industrial purposes.

In this alkaline storage battery, most of the positive electrodes are nickel electrodes, although some of them are air electrodes or silver oxide electrodes. In addition, the characteristics were improved from the pocket type to the sintered type, and it became possible to further seal and expand the applications. On the other hand, as the negative electrode, in addition to cadmium, zinc, iron, hydrogen, etc. are targeted.

Recently, in order to achieve a higher energy density, a nickel-hydrogen storage battery using a hydrogen storage alloy electrode as a negative electrode has received attention, and many proposals have been made for its production method and the like.

As a method for producing the hydrogen storage alloy electrode, there are a method of sintering alloy powder and a paste method of filling or coating a porous support such as foamed, fibrous or punched metal. . Of these, the paste method is the easiest to manufacture. The hydrogen storage alloy is relatively excellent in electron conductivity like the cadmium electrode and the zinc electrode, and thus has a high possibility of being used as a non-sintered electrode. That is, it is formed into a paste with a binder and is filled or adhered to a porous conductive plate having a three-dimensional or two-dimensional structure.

Among them, in order to improve the characteristics of the hydrogen storage alloy electrode, for example, a technique of forming a porous metal layer by plating the particle surface of the hydrogen storage alloy powder with nickel or copper is particularly resistant to oxidation. , Known to improve utilization, moldability. Further, in order to improve the characteristics, a process such as heat treatment in a vacuum after making the alloy or immersing in an alkaline solution has been proposed.

Further, in the case of applying to a closed type, it has been attempted to add a fluorine resin or a catalyst in order to improve the absorption of oxygen gas generated from the positive electrode during overcharge.

[0008]

However, when the above hydrogen storage alloy electrode is used for the storage battery, the charge / discharge characteristics, life characteristics, utilization rate, or high rate discharge characteristics at the beginning of the charge / discharge cycle are not sufficient. However, there is a problem that they need to be further improved.

In particular, the discharge capacity per weight of the alloy in the actual electrode was about 80% of the capacity of the alloy.

In consideration of the above problems of the prior art, the present invention has a high capacity, a high activity in which the utilization rate of the alloy is improved and the initial charge / discharge characteristics, life characteristics, or high rate discharge characteristics are improved. It is an object of the present invention to provide a method for producing a hydrogen storage alloy electrode and a hydrogen storage alloy electrode.

[0011]

According to the present invention of claim 1, hydrogen is formed by forming a hydrogen storage alloy material that electrochemically stores and releases hydrogen electrochemically on an electrode, and then plating the surface of the electrode with an alloy of nickel and tin. This is a method for manufacturing an occlusion alloy electrode.

The present invention according to claim 4 provides a hydrogen storage alloy electrode, the surface of which is plated with an alloy of nickel and tin.

[0013]

In the present invention, by plating the surface of the hydrogen storage alloy with an alloy of nickel and tin, the capacity of the electrode can be increased, the rapid charge / discharge characteristics and the life can be improved.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings showing its embodiments.

As the hydrogen storage alloy, the main alloy phase is C1.
Zr, one of the type 5 Laves phase alloys
An Mn _0.5 V _0.2 Co _0.1 Ni _1.2 alloy was used.

First, the production of electrodes will be described. Average particle size 2 obtained by crushing the above hydrogen storage alloy with a jet mill
1% by weight of polyethylene powder is added to the powder of 5 μm, and the mixture is made into a paste with ethanol. Then, this paste was filled in a foamed nickel plate having a porosity of 95% and a thickness of 0.8 mm,
An electrode was obtained by applying pressure. This was plated using a plating bath composed of nickel sulfate, tin sulfate or the like. The tin contents in the plating phase were 5, 30 and 50% by weight, respectively. This is an embodiment of the present invention, and is referred to as electrodes A, B, and C, respectively. The amount of plating was 5% by weight with respect to the amount of hydrogen storage alloy.

In order to compare the characteristics of this electrode, an electrode by a conventional method was also manufactured. That is, as in the conventional method, ZrMn _0.5 V _0.2 Co _0.1 Ni is similarly used.
_The alloy powder obtained by crushing the hydrogen storage alloy having the composition of _1.2 ,
An electrode was formed in the same manner as in the above-mentioned embodiment. This is designated as an electrode D as a comparative example by the conventional method. Further, in order to see the effect of adding tin, an electrode plated only with nickel was also manufactured as a comparative example. This is an electrode E.

The electrode prepared as described above is used as a negative electrode, a nickel oxide electrode having an excessive electric capacity is arranged as a positive electrode, and an aqueous solution of potassium hydroxide having a specific gravity of 1.30 is used as the electrolytic solution. Charging and discharging were performed under an open system in which the capacity was regulated with a hydrogen storage alloy negative electrode. Charging is 100 mA x 5.5 hours per 1 g of hydrogen storage alloy, discharging is alloy 1
The terminal voltage was set to 0.8 V at 50 mA per gram.

The change in discharge capacity at this time is shown in FIG.
Here, the electrode D manufactured by the conventional method, which had not been treated, had a saturation capacity of 0.351 Ah / g, and it took 5 cycles to reach the saturation capacity. Further, the electrode E plated only with nickel had a slightly increased saturation capacity of 0.362 Ah / g, but it took 5 cycles to reach this capacity. However, the discharge capacities of the electrodes A, B, and C of this example plated with nickel-tin alloy improved from the first cycle, and all exceeded 0.38 Ah / g. Especially tin content 3
0% by weight of electrode B showed a discharge capacity of 0.383 Ah / g. In addition, the deterioration of the capacity due to the cycle of the other electrodes was smaller than that of the non-plated electrode D.

Next, the result of constructing a sealed battery using these electrodes will be described. The above electrodes A, B,
Each of C, D and E was adjusted to have a width of 3.3 cm, a length of 21 cm and a thickness of 0.52 mm, and lead plates were attached at predetermined two positions. Then, in combination with the positive electrode and the separator, it was made into a cylindrical three-layer spiral shape and housed in an SC size battery case. As the positive electrode at this time, a known foaming nickel electrode was selected and used with a width of 3.3 cm and a length of 16 cm. Also in this case, the lead plates were attached at two places. As the separator, a polypropylene non-woven fabric having hydrophilicity was used.
As an electrolytic solution, 30 g / l of lithium hydroxide was dissolved in an aqueous potassium hydroxide solution having a specific gravity of 1.30 and used. This was sealed to form a sealed battery. The battery thus configured has a nominal capacity of 3.0 Ah according to the positive electrode capacity regulation. In this sealed battery, the battery composed of the electrode A of the hydrogen storage alloy electrode is referred to as battery A, and the batteries composed of the electrodes B, C, D and E are referred to as batteries B, C, D and E, respectively.

The results of evaluations made by charge / discharge cycle tests of 10 of each of these batteries will be described.

First, the initial discharge voltage and capacity were compared.
When a constant current charge of 150% of capacity at a rate of 5 hours and a constant current discharge up to 1.0 V at a rate of 5 hours were performed at 20 ° C., the average discharge voltage of the batteries A, B and C was 1.28 V. The discharge capacity was about 3.0 Ah from the first cycle. However, in batteries D and E, the average discharge voltage was 1.20 V and 1.22 V, respectively, and the discharge capacity did not reach 3.0 Ah in one cycle, and the positive electrode regulation was applied from the second cycle.

Next, the high rate discharge characteristics at low temperature were compared.
Charging was performed at 20 ° C. for 5 hours to 150% of the battery capacity, and then discharged at 0 ° C. for 1 hour to compare the capacities up to 1.0V. As a result, the battery D discharged only 48% with respect to the standard capacity, the average discharge voltage was 1.06 V, and the battery E was 61% and 1.08 V, while nickel-tin plating was performed. Batteries A, B, and C using the electrodes had a discharge capacity ratio of 82, 89, and 85%, and the average discharge voltage was all about 1.15V.

Further, the life characteristics were compared by charging / discharging at a constant current of 150% at a 1/2 hour charge rate and 1.0 V at a 1/2 hour discharge rate. The result is shown in FIG. Discharge capacity is battery A
Is 300% in the initial 96%, and 600 cycles is 8
8%, Battery B is 300 cycles, initial 97%, 600
92% in cycle, battery C is 300 cycles and initial 9
6%, 89% at 600 cycles, Battery D reached negative electrode rate limiting at 300 cycles and the capacity decreased to the initial 80%, and Battery E reached 91% at 300 cycles and 77% at 600 cycles. Therefore, the hydrogen storage alloy electrode according to the present invention has improved life characteristics. Incidentally, the tin content in the plating phase is preferably 5 to 60% by weight, and when the tin content in the plating exceeds 60%, the remarkable effect of nickel plating alone cannot be obtained.

Further, mixing the nickel-tin alloy powder into the hydrogen storage alloy does not have a remarkable effect, and it is considered that it is effective that the plating covers the electrode surface like a film to form a network. To be Regarding the effect of addition of tin, it is considered that, in addition to the catalytic effect of nickel, the malleability of tin is because the alloy is plated with good adhesion even if the hydrogen storage alloy is pulverized.

As described above, when the hydrogen storage alloy is used as the electrode, the actual discharge capacity of the electrode is 80 compared with the discharge capacity of the ideal electrode in which a large amount of Ni powder and alloy powder are mixed. %, But by plating the hydrogen storage alloy with an alloy of nickel and tin, the capacity of the electrode can be increased, the rapid charge / discharge characteristics, and the life can be improved.

In the above embodiment, as the hydrogen storage alloy, the main alloy phase is C15 type Laves.
ZrMn _0.5 V _0.2 Co _0.1 Ni _1.2 alloy, which is one of the phase alloys, was used, but the invention is not limited to this, and the general formula of other compositions is A
It is represented by Bα (α = 1.5 to 2.5), and the alloy phase substantially belongs to the Laves phase of the intermetallic compound,
AB ₂ Lav, a hydrogen storage alloy whose crystal structure is hexagonal C14 type or (and) cubic C15 type
Not to mention es phase alloy, MmNi _3.7 Mn _0.3 Al
Similar effects were obtained when an AB ₅ type hydrogen storage alloy having a CaCu ₅ structure such as _0.3 Co _0.7 was used.

[0028]

As is apparent from the above description, according to the present invention, after the hydrogen storage alloy material is formed into an electrode, the electrode surface is plated with an alloy of nickel and tin, so that the utilization factor of the alloy is improved, It has the advantage that the initial charge / discharge characteristics, life characteristics, or high rate discharge characteristics are improved.

[Brief description of drawings]

FIG. 1 is a diagram comparing discharge characteristics in an open system between an example according to the present invention and a conventional example.

FIG. 2 is a diagram comparing the life characteristics of a sealed battery of the same example and a conventional example.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tsutomu Iwaki 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A method for producing a hydrogen storage alloy electrode, which comprises forming an electrode of a hydrogen storage alloy material capable of electrochemically storing and releasing hydrogen electrochemically, and plating the surface of the electrode with an alloy of nickel and tin. 2. The general formula of the main hydrogen storage alloy is ABα.
(Α = 1.5 to 2.5), the alloy phase substantially belongs to the Laves phase of the intermetallic compound, and the crystal structure thereof is C14 type with hexagonal symmetry and / or C with cubic symmetry.
15. The method for producing a hydrogen storage alloy electrode according to claim 1, wherein the method is a 15 type. 3. The ratio of tin to nickel in the plated alloy is 5 to 60% by weight.
A method for producing the hydrogen storage alloy described. 4. A hydrogen storage alloy electrode having a surface coated with an alloy of nickel and tin.