JP2983426B2 - Production method and electrode for hydrogen storage alloy - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for reversibly storing and storing hydrogen.
The present invention relates to a method for producing a hydrogen storage alloy to be released and an electrode using the same.

[0002]

2. Description of the Related Art Various applications have been attempted for hydrogen storage alloys, mainly as materials for storing, transporting and purifying hydrogen, energy conversion materials such as heat and pressure, and electrode materials for alkaline storage batteries. As the hydrogen storage alloy material used for these, many alloy materials have been proposed so far, and typical ones are LaNi ₅ , TiMn _1.5 , Ti
Fe, Mg ₂ Ni and the like are well known. In recent years, the performance as a hydrogen storage alloy has been further improved by a multi-element alloy obtained by adding third, fourth, fifth, and other new elements based on these materials.

[0003] On the other hand, with the remarkable development of portable equipment in recent years, there is a remarkable demand for a battery used for the portable equipment. In order to enable miniaturization and weight reduction, further higher energy density batteries are required. These requirements are the same in the field of electric vehicles and various mobile power supplies. Heretofore, lead storage batteries and alkaline storage batteries represented by nickel-cadmium storage batteries have been widely used as storage batteries among various power sources. Recently, an alkaline storage battery such as a nickel-hydrogen storage battery using a hydrogen storage alloy that reversibly stores and releases hydrogen as an electrode material has attracted attention. The hydrogen-absorbing alloy electrode used in this method can be used to construct a battery with the same handling as cadmium and zinc, and has a higher energy density because the actual dischargeable capacity density can be larger than cadmium and there is no formation of dendrites like zinc. It is promising as an electrode for alkaline storage batteries with high density, long life and no pollution.

[0004] The hydrogen storage alloy used for these electrodes is:
Usually, it was produced by an arc melting method, a high-frequency induction heating melting method, or the like. Then, the hydrogen storage alloy obtained by melting is usually pulverized into a powder form, and then subjected to pressure molding,
The electrode is formed by a method of sintering, or a method of forming a paste into a paste and applying the paste to a porous support. As an example using this type of electrode, there is a sealed nickel-hydrogen storage battery using a nickel electrode as a positive electrode, a hydrogen storage alloy electrode as a negative electrode, and an aqueous solution of potassium hydroxide as an electrolyte. This battery has a nominal battery voltage of 1.2 V, is compatible with nickel-cadmium storage batteries, has the advantage of being handled in the same manner, and has an energy density of about 1.5 times that of nickel-cadmium storage batteries for similar battery sizes. It has the feature of high energy density and it is coming to practical use gradually.

The hydrogen storage alloy materials used for these electrodes include LaNi ₅ and MmNi.
Alloys having _{a CaCu 5} structure _{based on 5} are well known. For electrodes, MmNi _3.8 Co _0.5 Mn _0.4
An example is an _Al0.3 alloy. When these alloys having the CaCu ₅ structure are charged and discharged electrochemically, the obtained discharge capacity density is almost limited to about 0.3 Ah per 1 g of the alloy. To increase the energy density of batteries,
Is essential higher capacity of the hydrogen storage alloy used for the electrodes, as an alloy having a potential for higher capacity, the alloy having a AB ₂ type Rabasu (Laves) phase structure is expected. As an alloy having a specific electrode for AB ₂ type Rabasu phase _{structure, ZrMn 0.6 Cr 0.1 V 0.2 Ni} 1.2
Alloys and the like.
It has a discharge capacity density of about 4 Ah / g. An alloy having an AB ₂ type Larbus phase structure, for example, ZrMn
The production of _0.6 Cr _0.1 V _0.2 Ni _1.2 alloy is performed by mixing simple metals such as Zr, Mn, Cr, V, and Ni as starting materials so as to have a desired alloy composition, and using an arc melting method or high-frequency induction heating melting. It was common to dissolve directly by a method.

[0006]

To increase the capacity of the hydrogen storage alloy electrodes [0005], it is advantageous to use an alloy having a AB ₂ type Rabasu phase structure such as ZnMn _0.6 Cr _0.1 V _0.2 Ni _1.2 alloy is there. In order to achieve higher capacity, it is necessary to manufacture a single and homogeneous alloy.

However, in practice, it has been difficult to produce a single, homogeneous alloy having the desired composition due to insufficient homogeneity or the formation of another segregated phase. The biggest cause is that there is a difference in solubility due to the melting point and shape of each metal element. Other causes include reactivity with a crucible during melting, composition deviation due to a difference in vapor pressure of each metal, generation of precipitates due to solidification of a molten metal, and the like.

Further, since the simple substance of V metal requires a complicated refining process in its production, the material price of V metal is very high. It would be economically advantageous if V could be used as an alloy containing other metals. The present invention aims to provide a method for producing at low cost an alloy having a AB ₂ type Rabasu phase structure comprising at least vanadium and nickel, as a single homogeneous alloy.

[0009]

SUMMARY OF THE INVENTION The present invention provides a method for producing a hydrogen storage alloy containing at least vanadium and nickel and having a main alloy phase of a C14 type or C15 type Larvas phase structure, wherein the step of melting the raw materials comprises And vanadium is supplied as a vanadium alloy obtained by alloying at least nickel with nickel.

More specifically, the present invention uses a vanadium alloy containing at least nickel as a starting raw material, and uses a general formula ABβ (where β is the atomic ratio of B element to A element, ≦ β ≦ 2.5, A is Zr alone or Ti, Hf, Ta, Y, Ca, Mg, La, C
e, Nd, Nb, Mo, Al and Zr and B containing at least one element selected from the group consisting of 40 atomic% are N
i and V are essential components, and Mg, Ca, T
i, Hf, Nb, Cr, Mo, Mn, Fe, Co, P
d, Cu, Ag, Zn, Cd, Al, Si, La, C
e, Pr and Nd), wherein the main alloy phase is an alloy having a C14 type or C15 type Larbus phase structure, and its crystal lattice constant is C14 type. This is a method for producing an alloy in which a = 4.8 to 5.2 angstroms, c = 7.9 to 8.3 angstroms, and in the case of the C15 type, a = 6.92 to 7.30 angstroms.

The vanadium alloy used here is 10 to 9
It is preferable to use a V-Ni alloy mainly containing vanadium and nickel containing 0 wt% of V. Further, in the method for producing the hydrogen storage alloy of the present invention, the production method is a method selected from a casting method, a gas atomizing method, a centrifugal spray method, and a roll quenching method.
It is desirable to carry out ultra-rapid cooling at a rate of 00 ° C./sec or more.

[0012]

When a V-Ni alloy mainly composed of vanadium and nickel is used as a starting material for producing an alloy having a Labus phase structure in which the main alloy phase of the hydrogen storage alloy is C14 or C15, the homogeneity of the alloy can be improved. The performance is clearly improved. Probably, the solubility of the alloy is improved by using a raw material in which V, which is relatively difficult to dissolve, is alloyed with Ni necessary for the hydrogen storage alloy.
In addition, the manufacturing method of the alloy by the ultra-quenching method in which the cooling rate until solidification is selected from the casting method, gas atomizing method, centrifugal spraying method and roll quenching method is 1000 ° C./sec or more improves the homogeneity of the alloy itself. There is an effect, this and V-Ni
Combination with the use of alloys is even more effective in improving performance. Also, by adding the necessary V metal in the form of a V-Ni alloy, the raw material cost of the alloy can be reduced to less than half the value in the case of using V alone, and the economic effect is large.

[0013]

The present invention will be described below with reference to examples. [Example 1] ZrMn _0.6 Cr _0.1 V was used as a hydrogen storage alloy having a Lavase phase structure in which the main alloy phase was C15.
_{A 0.2} Ni _1.2 alloy was chosen. As a method for producing this alloy, commercially available Zr, Mn having a purity of 99.5% or more,
A conventional method using each elemental metal of V, Cr and Ni;
A case was compared in which a V-Ni alloy having a composition of 0 wt% V and 30 wt% Ni was used, and the other elements were elemental metals.

With these two starting materials, ZrMn _0.6
Each metal raw material was blended so as to be a Cr _0.1 V _0.2 Ni _1.2 alloy. First, ZrMn _0.6 Cr _0.1 V _0.2 Ni
_1.2 To prepare an alloy, wt% of a single metal constituting the alloy was Zr = 43.4 wt% and Mn = 15.7 wt%.
%, Cr = 2.5 wt%, V = 4.9 wt%, Ni = 3
3.5 wt% is required. When using each elemental metal, the weight of each elemental metal was adjusted with this wt%. 70w
When a V-Ni alloy having a composition of t% V and 30 wt% Ni was used, the entire amount of V was adjusted with the V-Ni alloy, and the insufficient portion of Ni was adjusted with a single Ni metal. The raw materials thus mixed were melted four times each while being inverted by an argon arc melting furnace. The alloy ingot obtained by melting was subjected to a heat treatment at 1000 ° C. for 6 hours in a vacuum of 10 ⁻³ Pa.

The alloy ingot thus obtained was used for electrode evaluation and alloy analysis. First, the results of the electrode evaluation will be described. The electrodes used for this evaluation were produced as follows.
First, each alloy was mechanically pulverized to 200 mesh or less, and a 1 wt% aqueous solution of carboxymethyl cellulose and 2 w
A t% aqueous solution was added and mixed to form a paste. This paste-like composition was almost uniformly filled in a foamed nickel porous body having a thickness of 1 mm and a porosity of 95%, and then dried to form an electrode. Each of the thus obtained hydrogen storage alloy electrodes was pressurized by a press, cut into a size having an alloy amount of 2 g, and a lead plate was attached by spot welding.

A single plate test was carried out on the hydrogen storage alloy electrodes produced using these alloys in an open type with abundant electrolyte. As an electrolyte, an aqueous solution of caustic potassium having a specific gravity of 1.30 was used, and charging and discharging were repeated using a sintered nickel electrode having an excess capacity as a positive electrode and a hydrogen storage alloy electrode as a negative electrode, and the change in discharge capacity of the negative electrode was examined. . The charge and discharge conditions were 20 ° C., charging at 0.2 A for 5.5 hours, discharging at 0.1 A and battery voltage up to 0.8 V. The result is shown in FIG. FIG.
The horizontal axis shows the number of charge / discharge cycles, and the vertical axis shows the discharge capacity per 1 g of the alloy. As is clear from FIG.
Comparing the properties of the tested hydrogen storage alloy electrodes, VN
The electrode A produced by the alloy method using i (the method of the present invention) has a larger discharge capacity than the electrode B produced by the alloy method using each elemental metal (the conventional method), has a faster rise in the discharge capacity in the initial stage of charging and discharging, and It can be seen that the discharge capacity is stable in repeated charge / discharge tests.

Next, a description will be given of the results of an evaluation made by constructing a sealed battery using the electrodes A and B described above. Using a known foamed nickel electrode as a counter electrode and a polypropylene non-woven fabric subjected to hydrophilic treatment for the separator, the three layers of the negative electrode, the separator, and the positive electrode are spirally inserted into the battery case to produce a cylindrical sealed nickel-hydrogen storage battery. did. An electrolyte obtained by dissolving 25 g / 1 of lithium hydroxide in an aqueous solution of caustic potassium having a specific gravity of 1.25 was injected into the battery case, and then sealed. This sealed battery is an AA type and has a battery capacity of 1.3.
Ah. The battery constituted by using the electrode A is denoted by a, and the electrode B is denoted by
Each of the sealed batteries was prepared as 5 cells, with the battery constituted by using b as b. First, charging and discharging were performed for 5 cycles under relatively mild conditions. Then, it was confirmed that each of the batteries had a standard discharge capacity of about 1.3 Ah. Then, while measuring the internal pressure of the battery at the time of charging and discharging, 20
A charge / discharge cycle test was performed in which charging was performed at 1.3 A (1 C) for 1.5 hours and discharging was similarly performed at 1.3 A (1 C) up to a battery voltage of 1.0 V at 100C.

As a result of the charge / discharge cycle test, changes in the discharge capacity of the battery and the maximum internal pressure of the battery during the charge / discharge cycle are shown in FIGS. 2 and 3, respectively. As is clear from FIGS. 2 and 3, the battery a using the alloy according to the present invention was subjected to a charge / discharge cycle test up to 450 cycles.
Both the discharge capacity and the maximum internal pressure of the battery showed the same results as those at the initial stage, proving that the battery had a long life. On the other hand, in the battery b, the internal pressure of the battery was rapidly increased after 300 cycles, and the battery discharge capacity was also sharply reduced. From the above results, by producing a hydrogen storage alloy using a V-Ni alloy as a starting raw material of vanadium, the characteristics of the electrode and the battery can be improved despite the same alloy composition and the same electrode and battery configuration as before. It can be significantly improved.

Next, the results of alloy analysis will be described. X-ray diffraction measurement of each alloy pulverized to 400 mesh or less for alloy A (invention method) using an alloy manufacturing method using a V-Ni alloy and alloy B (conventional method) using an alloy manufacturing method using each single metal, The alloy structure of the lump was observed, and the amount of occluded hydrogen gas was measured. As a result of X-ray diffraction of each of the alloys, the main alloy phases were all alloys having a C15-type Larvas phase structure. However, comparing these two alloys more finely, it was found that alloy A had a larger relative ratio of the effective Labus phase and a sharper diffraction peak than alloy B. In addition, the alloy structure was examined with a scanning electron microscope, and the structural element distribution was examined with an X-ray microanalyzer. As a result, it was found that both of the two alloys had innumerable island-like precipitates in addition to the main phase of the Lavas phase. Was observed. Further, when the element distribution was examined more precisely, it was confirmed that the distribution of the concentration of each element in the Labus phase, which is the main phase, in alloy B had a considerable difference in location. On the other hand, in the alloy A, the distribution of the concentration of each element was relatively averaged in place. Further, in the measurement of the hydrogen storage amount, it was found that the alloy A increased the hydrogen storage amount by about 4% as compared with the alloy B. From this, it was found that the alloy A was more homogeneous and the actual hydrogen storage capacity was also improved.

Example 2 As a hydrogen storage alloy, the same ZrMn _0.6 Cr _{0.1 V 0.2} as the alloy shown in Example 1 was used.
Select Ni _1.2 alloy and use 70wt% as starting material
% V, a V-Ni alloy having a composition of 30 wt% Ni was used, and unlike the previous argon arc melting furnace, an alloy was produced using a gas atomizer using an argon gas. As is well known, in the alloy manufacturing method using the gas atomization method, the cooling rate in the solidification process is extremely high as compared with the arc melting method in Example 1, and the cooling rate is estimated to be about 10 ⁴ to 10 ⁵ ° C./sec. .

An alloy powder obtained by using this V-Ni alloy and obtained by an alloy manufacturing method by a gas atomizing method was subjected to electrode evaluation and alloy analysis in a form to be compared with the alloy shown in Example 1 above. Therefore, the same conditions as in Example 1 were used for the evaluation of the alloy in the electrode and the battery. First, the results of the electrode evaluation will be described. An electrode made of an alloy using a V-Ni alloy and obtained by an alloy manufacturing method using a gas atomization method has a further capacity of about 0.03 Ah / g as compared with the electrode A.
Increased. The stability due to other rising and repeated charging and discharging was almost the same as that of the electrode A. Similarly, a sealed battery using this alloy was evaluated. As a result, FIG.
Similarly to the battery a of FIG. 3, during the charge-discharge cycle test up to 450 cycles, the discharge capacity and the maximum internal pressure of the battery showed completely the same results as those at the initial stage, proving that the battery has a long life. And the battery internal pressure showed a lower value than the battery a. From these results, it can be seen that when a V-Ni alloy is used as a starting material and a hydrogen storage alloy is produced by a super-quenching method using a gas atomization method, the electrode and battery characteristics are further improved.

Next, as a result of analyzing this alloy, X
According to the line diffraction measurement, it was a very clean single alloy having only the Labus phase of the C15 type. The crystal lattice constant of this alloy was a = 7.076 angstroms. Also, from the observation of the alloy structure, it was confirmed that the alloy was very homogeneous without any compositional deviation without any segregation phase or the like. In the evaluation of the hydrogen storage amount, the hydrogen storage amount was further improved by about 4% as compared with the alloy used for the electrode A. From the above results, it was confirmed that the alloy using the V-Ni alloy and obtained by the alloy manufacturing method using the gas atomization method had better performance.

In the above embodiment, a five-component system of Zr-Mn-V-Cr-Ni was used as the hydrogen storage alloy. However, the present invention is not limited to this embodiment, and those satisfying the following requirements are effective. That is, at least a vanadium-nickel (V-Ni) alloy is used as a starting material, and a general formula ABβ (β is an atomic ratio of B element to A element, and 1.5 ≦ β ≦ 2.
5. A is Zr alone or Ti, Hf, Ta, Y, C
a, Mg, La, Ce, Nd, Nb, Mo, Al and Si containing 40 at% of at least one element selected from the group consisting of Ni and V as essential components; Ti, Hf, Nb, Cr, Mo, M
n, Fe, Co, Pd, Cu, Ag, Zn, Cd, A
1, at least one selected from the group consisting of Si, La, Ce, Pr and Nd), wherein the main alloy phase is an alloy having a C14 type or C15 type Lurbus phase structure, and its crystal lattice constant Is a for C14 type
= 4.8-5.2 angstroms, c = 7.9-8.0.
For 3 angstrom, C15 type, a = 6.92 ~
It is advantageous to produce an alloy or hydride thereof that is 7.30 angstroms.

[0024] Among them, the alloy or the hydride thereof is particularly preferably substantially the same as the general formula Zr1-αTiαMnβNi.
γMδ (where M is V as an essential element and Cr, Mo,
At least one element selected from the group consisting of Fe, Co, Cu, and Al is contained, and 1-α, α, β, γ, and δ are represented by the atomic ratios of Zr, Ti, Mn, Ni, and M elements, respectively.
= 0-0.4, β = 0.01-0.8, γ = 0.8-
1.5, δ = 0.01-0.5 and β + γ + δ = 1.
The alloys represented by 8 to 2.3) are desirable in terms of performance.

The V-Ni alloy mainly composed of vanadium and nickel used as a starting material is 10 to 90 watts.
Including t% V was effective in terms of homogeneity and performance of the resulting alloy. Less than 10 wt% and 90
An alloy produced using a V-Ni alloy containing V in excess of wt% does not always have sufficient effects of the present invention. When a Zr-Ni alloy mainly composed of zirconium and nickel is used as a starting material in addition to the V-Ni alloy, the solubility of Zr, which is difficult to dissolve similarly to V, is improved, and the performance is further improved. Is achieved. Furthermore, in the previous example, the production of the alloy was described by the arc melting method and the gas atomization method, but the production method was a method selected from a casting method, a gas atomization method, a centrifugal spray method, and a roll quenching method, and until solidification. It is preferable to perform the cooling by ultra-rapid cooling at a cooling rate of 1000 ° C./sec or more.

[0026]

As described above, according to the present invention, it is possible to improve the homogeneity of a hydrogen storage alloy whose main alloy phase has a C14 type or C15 type Larvus phase structure, thereby increasing the hydrogen storage amount. Can be. Therefore, the electrode using the hydrogen storage alloy has an improved discharge capacity and a longer life. Further, according to the present invention, the raw material cost of the alloy can be significantly reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a change in discharge capacity of an electrode using a hydrogen storage alloy obtained according to an example of the present invention and an alloy of a comparative example with a charge / discharge cycle.

FIG. 2 is a diagram illustrating a cylindrical sealed nickel alloy according to an embodiment of the present invention.
FIG. 4 is a diagram showing a change in discharge capacity with a charge / discharge cycle of a hydrogen storage battery.

FIG. 3 shows a cylindrical sealed nickel alloy according to an embodiment of the present invention.
FIG. 5 is a diagram showing a change in the maximum battery internal pressure according to a charge / discharge cycle of the hydrogen storage battery.

──────────────────────────────────────────────────の Continued on the front page (72) Inventor Tokukatsu Akutsu 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. In-company (56) References JP-A-2-10659 (JP, A) JP-A-60-228633 (JP, A) JP-A-7-216475 (JP, A) (58) Fields investigated (Int. . ^6, DB name) C22C 1 / 00,16 / 00 C22C 19 / 00,27 / 02 C01B 3/00 H01M 4 / 24,4 / 26,4 / 38

Claims (3)

(57) [Claims] 1. A method for producing a hydrogen storage alloy containing at least vanadium and nickel and having a main alloy phase of a C14 type or a C15 type Larvas phase structure, wherein in the step of melting the raw material, vanadium contains at least n
Alloyed with nickel and vanadium in a total amount of 10 to 90 wt%
A method for producing a hydrogen storage alloy , comprising supplying as a vanadium alloy containing : 2. A method of dissolving a raw material as a vanadium alloy obtained by alloying vanadium with at least nickel to obtain a general formula ABβ (where β is an atomic ratio of element B to element A, and 1.5 ≦ β ≦ 2.5,
A is Zr alone or Ti, Hf, Ta, Y, Ca, M
g, La, Ce, Nd, Nb, Mo, at least one of including Zr selected from the group consisting of Al and Si, B is an essential component of Ni and V, Mg in addition to this, Ca,
Ti, Hf, Nb, Cr, Mo, Mn, Fe, Co, P
d, Cu, Ag, Zn, Cd, Al, Si, La, C
e, Pr and Nd), and the main alloy phase is an alloy having a C14 type or C15 type Larbus phase structure, and its crystal lattice constant is C14 type. Hydrogen storage characterized by producing an alloy having a = 4.8 to 5.2 angstroms, c = 7.9 to 8.3 angstroms, and a = 6.92 to 7.30 angstroms for C15 type. Alloy manufacturing method. 3. The alloy according to claim 1, wherein said alloy substantially has the general formula: Zr1-αTi
αMnβNiγMδ (where M is V as an essential element,
Containing at least one element selected from the group consisting of Cr, Mo, Fe, Co, Cu and Al, 1-α, α,
β, γ, and δ are the atomic ratios of the elements Zr, Ti, Mn, Ni, and M, respectively, α = 0 to 0.4, β = 0.01 to 0.8, γ
= 0.8-1.5, δ = 0.01-0.5 and β + γ
3. The method for producing a hydrogen storage alloy according to claim 2 , wherein + δ = 1.8 to 2.3).