JPH07111152A - Evaluation method for hydrogen storage alloy for electrode - Google Patents

Abstract

PURPOSE:To quickly, accurately evaluate electrode performance by previously making a calibration curve showing the relation of electrode performance to a specific parameter, and comparing the parameter of an objective hydrogen storage alloy with the calibration curve. CONSTITUTION:When the capacity maintenance factor of each test electrode is estimated from a parameter PA, a calibration curve showing correlation between each capacity maintenance factor obtained from actual measurement of test electrodes A1, A3, and A6 and the parameter PA is obtained by a non- linear least square method. The capacity maintenance factors of electrodes A2, A4, and A5 are estimated from the calibration curve, and the capacity maintenance factors estimated are compared with those obtained by actual measurements. The capacity maintenance factors of the electrodes A2, A4, and A5 estimated from the calibration curve extremely approximate to the capacity maintenance factors of the test electrodes. By using the parameter P4, the capacity maintenance factor is estimated with high accuracy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for evaluating a hydrogen storage alloy for electrodes.

[0002]

2. Description of the Related Art In recent years,
A hydrogen storage alloy electrode that uses a hydrogen storage alloy that can reversibly store and release hydrogen as an electrode material is lighter in weight and higher in capacity than lead electrodes and cadmium electrodes that have been widely used in the past. Because of its potential, it is in the spotlight as a negative electrode for next-generation alkaline secondary batteries.

The hydrogen storage alloy used for the hydrogen storage alloy electrode must generally be capable of reversibly storing and releasing hydrogen in the vicinity of room temperature. The main hydrogen storage alloys currently in practical use are: It is a CaCu ₅ type alloy having a basic structure of LaNi ₅ or MmNi ₅ . Others, C14Lav
Since the AB ₂ type alloy having the es structure also has the possibility of increasing the capacity, research for its practical use has been vigorously made.

By the way, various characteristics such as the degree of activation at the beginning of the cycle, the corrosion resistance, the initial electrode capacity, and the charge / discharge cycle characteristics (capacity retention rate) are regarded as important in the hydrogen storage alloy electrode. Each time, the electrode characteristics were evaluated by actually producing electrodes, assembling batteries, and conducting various battery tests.

However, the production conditions for hydrogen storage alloys are as follows:
For example, if the roll peripheral speed in the liquid quenching method, the gas ejection speed in the gas atomizing method, the cooling water temperature during casting in the casting method, etc., are slightly different, the physical properties of the hydrogen storage alloy produced will fluctuate. There will be variations. Therefore, for quality control, it is necessary to actually assemble an evaluation battery for each manufacturing lot to evaluate various characteristics of the hydrogen storage alloy as an electrode material, but this evaluation requires a long period of time. For this reason, conventionally, there has been a strong demand for the development of a method capable of quickly and highly accurately predicting the characteristics of an electrode hydrogen storage alloy as an electrode material without actually assembling the battery.

Therefore, as a result of earnest studies on the physical properties of various hydrogen storage alloys for electrodes in order to meet such demands, the present inventors have found that the composition or lattice constant of the hydrogen storage alloy and the electrode characteristics are clear. Although there is no significant correlation, there is a clear correlation between specific parameters and electrode characteristics obtained by analyzing data based on the results of X-ray diffraction measurement of the hydrogen storage alloy to be evaluated. Found that there is.

The present invention has been made on the basis of such findings, and an object of the present invention is to evaluate a hydrogen storage alloy for an electrode capable of quickly and highly accurately evaluating the electrode characteristics. To provide.

[0008]

A method of evaluating a hydrogen storage alloy for an electrode according to the present invention for achieving the above object has a lattice plane (h.k.l.) having a selective orientation. , A hydrogen storage alloy M for making a plurality of calibration curves having the same alloy composition as the hydrogen storage alloy E to be evaluated and different alloy structures from each other
_1, M _2, ..., the value P ₁ of the parameter P of the function F (phi) in satisfying the following formula (C) for the _{M X, P 2, ...,} P X
Is the hydrogen storage alloys M ₁ , M ₂ , ..., M for preparing the calibration curve.
An arbitrarily selected lattice plane (h ₁ k ₁ l ₁ ) plane, (h ₂ k ₂ l ₂ ) plane, between _X and the reference hydrogen storage alloy S, ...,
Integrated intensity ratio I _{M1 (h1k1l1)} / I _{s (h1k1l1)} , I _{M2 (h2k2l2)} / I of X-ray diffraction peaks on the (h _X k _X l _X ) plane
_{s (h2k2l2)} , ..., I _{MX (hXkXlX)} / I _{s (hXkXlX)} , and
The lattice planes (h ₁ k ₁ l ₁ ) plane, (h ₂ k ₂ l ₂ ) plane,
_{..., (h X k X l} X) plane and the lattice plane (h.k.l.)
The step (1) to obtain by substituting the angles φ ₁ , φ ₂ , ..., φ _X formed with the surface into I _(hkl) / I _{s (hkl)} and φ in the following formula (C), respectively, P ₁ , P ₂ , ... _, P
and _x, the calibration curve for the hydrogen storage alloy M _1, M _2, ...,
Measured values T ₁ , T ₂ , representing the characteristics of M _{X as} an electrode material,
_, Step (2) of creating a calibration curve showing the correspondence with T _X, and the value P _{E of the} parameter P for the hydrogen storage alloy E to be evaluated, the hydrogen storage alloy E to be evaluated, and Arbitrarily selected lattice planes (h _E1 k _E1 l _E1 ), (h _E2 k _E2 l _E2 ) with the reference hydrogen storage alloy S
, ..., (h _EY k _EY l _EY ) X-ray diffraction peak integrated intensity ratio I _{E1 (hE1KE1lE1)} / I _{s (hE1kE1lE1)} , I
_{E2 (hE2KE2lE2)} / _{Is (hE2kE2lE2)} , ..., I
_{EY (hEYKEYlEY)} / _{Is (hEYkEYlEY)} and the lattice planes (h _E1 k _E1 l _E1 ) face, (h _E2 k _E2 l _E2 ) face, ..., (h _EY
The angles φ _E1 , φ _E2 , ..., φ _EY formed by the k _EY l _EY ) plane and the lattice plane (h.k.l.) plane are respectively expressed by I in the following formula (C).
_(hkl) / I _{s (hkl)} and the step (3) obtained by substituting for φ, and by comparing the P _E with the calibration curve, the characteristics of the hydrogen storage alloy E to be evaluated as an electrode material are evaluated. Estimating step (4).

F (φ) = I _(hkl) / _{Is (hkl)} (C)

[However, in the equation, I _(hkl) is a lattice plane (hk
1) hydrogen storage alloys M ₁ and M for preparing the calibration curve on the plane
₂ , ..., M _X or the integrated intensity of the X-ray diffraction peak of the hydrogen storage alloy E to be evaluated; I _{s (hkl)} is the X-ray diffraction on the lattice plane (hkl) plane of the reference hydrogen storage alloy S. The integrated intensity of the peak; F (φ) changes in accordance with the alloy structure of the hydrogen storage alloys M ₁ , M ₂ , ..., M _X for creating the calibration curve or the hydrogen storage alloy E to be evaluated, and their A function of φ having a parameter P that uniquely determines characteristics as an electrode material; φ is an angle (unit: radian) formed between the lattice plane (h.k.l.) plane and the lattice plane (hkl) plane Is. ]

Lattice planes (h _E1 k _E1 l _E1 ) planes, (h _E2 k _E2 l
_E2 ) plane, ..., (h _EY k _EY l _EY ) plane is a lattice plane (h ₁ k ₁
l ₁ ) plane, (h ₂ k ₂ l ₂ ) plane, ..., (h _X k _X l _X )
The lattice planes may be all different from the planes, but it is preferable that all or some of the lattice planes are the same. For the same lattice plane, the integrated intensity of the reference X-ray diffraction peak of the hydrogen storage alloy S obtained in step (1) is directly used as the integral of the X-ray diffraction peak of the reference hydrogen storage alloy S of step (3). This is because it can be used as strength.

P ₁ , P ₂ , ..., In step (1)
The value of P _{X and} the value of P _E in step (3) are
For example, for some φ, the integrated intensity ratios of the X-ray diffraction peaks of the hydrogen storage alloy for creating a calibration curve or the hydrogen storage alloy to be evaluated and the reference hydrogen storage alloy are obtained, and the φ and each φ The integrated intensity ratio is calculated by the above formula (C) [F
(Φ) = I _(hkl) / I _{s (hkl)} ] and substitute P ₁ , P ₂ ,
, P _X or P _E are set as unknowns, and the least squares method is applied to each of these formulas to obtain the most probable value.

As described above, there is no clear correlation between the composition and lattice constant of the hydrogen storage alloy and the electrode characteristics, but data based on the results of X-ray diffraction measurement of the hydrogen storage alloy. There is a clear correlation between the specific parameters and the electrode characteristics obtained by analyzing Therefore, if a calibration curve showing the correspondence between such parameters and electrode characteristics is obtained in advance, the parameter values of the hydrogen storage alloy to be evaluated are subjected to mathematical calculations such as X-ray diffraction measurement and least squares method. Thus, it is possible to quickly evaluate the electrode characteristics of the hydrogen storage alloy just by comparing the obtained value with the calibration curve.

In particular, when the function F (φ) in the present invention is a function of φ whose parameters P are P _A and P _B specified by the following equation (D), the degree of activation and charge / discharge are used. It is possible to accurately estimate the electrode characteristics such as the capacity retention rate after cycle, the corrosion resistance, and the capacity, to the same extent as in the actual machine test of the battery.

F (φ) = P _A + (1−P _A ) exp (−P _B · φ ² ) ... (D)

[Wherein P _A and P _B correspond to the alloy structures of the hydrogen storage alloys M ₁ , M ₂ , ..., M _x for preparing the calibration curve and the hydrogen storage alloy E to be evaluated in the present invention. It is a parameter that changes and uniquely determines the characteristics of the electrode material, and corresponds to the parameter P in the present invention described above. Further, φ is an angle (unit: radian) formed by the lattice plane (h.k.l.) plane and the lattice plane (hkl) plane in the present invention. ]

Hydrogen storage alloy E to be evaluated in the present invention
As, CaCu ₅ type (AB ₅ type) hexagonal crystal, MgNi
Typical examples include those having respective crystal structures such as type ₂ (AB ₂ type) hexagonal crystal, MgZn ₂ type (AB ₂ type) hexagonal crystal, and MgCu ₂ type (AB ₂ type) cubic. It is not limited to these.

As the component A of the hydrogen storage alloy having the AB ₅ type hexagonal crystal structure, there are La, Ce, Nd, Pr and Sm.
One or more rare earth elements and C selected from
a is exemplified, and as the B component, Cr, Mn, F
Examples include one or more kinds of transition elements selected from e, Co, Ni, Cu, Sn, Al and the like.

As the A component of the hydrogen storage alloy having the AB ₂ type hexagonal crystal structure, Ti, Zr, Cr, V,
One or more elements selected from alkaline earth metal elements such as Ca and Mg are exemplified, and the B component is Cr, Mn, Fe, Co, Ni, Cu, Sn, Al.
One or more transition elements selected from the above are exemplified.

[0020]

In the method of the present invention, a calibration curve showing the correspondence between the electrode characteristics and the specific parameter P is obtained in advance, and the parameter value of the hydrogen storage alloy E to be evaluated is collated with the calibration curve, A method of predicting the electrode characteristics of the hydrogen storage alloy is adopted. Therefore, the electrode characteristics of the hydrogen storage alloy E to be evaluated can be quickly estimated without actually assembling the battery.

[0021]

EXAMPLES The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by the examples described below, and various modifications may be made without departing from the scope of the invention. Is possible.

(Example 1) [Preparation of hydrogen storage alloy] Commercially available Mm (Misch metal:
(Mixture of rare earth elements), Ni, Co, Mn and Al are weighed and mixed in an element ratio of 1.0: 3.1: 0.9: 0.6: 0.4, and then arc melted in an argon gas atmosphere. did. Then, the alloy melt obtained by this arc melting was
10 ³ cm / sec, 2 × 10 ³ cm / sec, 3 × 1
0 ³ cm / sec, 4 × 10 ³ cm / sec, 5 × 10
^The compositional formula MmNi _3.1 Co _0.9 Mn _0.6 Al was dropped in order to solidify by dropping onto a roll rotating at a high speed at a peripheral speed of ³ cm / sec or 6 × 10 ³ cm / sec (liquid quenching method).
Hydrogen storage alloys AL1 to AL6 represented by _0.4 were obtained.

[Calculation of Parameters P _A and P _B ] From the X-ray diffraction patterns of the hydrogen storage alloys AL1 to AL6 and the reference X-ray diffraction pattern of the hydrogen storage alloys, the hydrogen storage alloys AL1 to AL6 and the selective orientation are selected. Various lattice planes (h ₁ k ₁ l ₁ ) with a hydrogen storage alloy that is a standard that has no
_, (H ₂ k ₂ l ₂ ) plane _, ..., (h _X k _X l _x ) plane, the integrated intensity ratios are calculated, and these integrated intensity ratios are I _(hkl) / I in the following formula (E). _{s (hkl)} , also hydrogen storage alloy A
L1-AL6 selective orientation planes (110) planes and lattice planes (h
₁ k ₁ l ₁ ) plane _, (h ₂ k ₂ l ₂ ) plane _, …, (h _X k _X
The angle φ ₁ , φ ₂ , ..., φ _X formed with the l _X ) plane is expressed by the following equation (E).
Parameter values P _A and P _B (H.Traya an) related to the selective orientation (alloy structure) of each hydrogen storage alloy.
d F. Maruo, Mineralogical Journal, Vol.10 (1981) 211)) was obtained using the nonlinear least squares method. Here, as the reference hydrogen storage alloy, the one having no selective orientation is used, but it is not always necessary, and one having selective orientation may be used. The results are shown in Table 1.

I _(hkl) / _{Is (hkl)} = P _A + (1−P _A ) exp (−P _B · φ ² ) ... (E)

[0025]

[Table 1]

[Assembly of Test Cell] Hydrogen Storage Alloy AL1
AL6 is mechanically crushed to an average particle size of about 150 μm,
A seed hydrogen storage alloy powder was obtained. Next, 1 g of each of these hydrogen storage alloy powders and 1.2 nickel powders as a conductive agent
g and polytetrafluoroethylene (PTFE) 0.2 g as a binder were mixed and rolled to obtain 6 kinds of alloy paste. Thereafter, a predetermined amount of each alloy paste was wrapped with nickel mesh and pressed to produce disk-shaped hydrogen storage alloy electrodes A1 to A6 having a diameter of 20 mm.

Next, each hydrogen storage alloy electrode was used as a test electrode (working electrode), and a cylindrical sintered nickel electrode having a sufficiently large electrochemical capacity for this test electrode was used as a counter electrode, and a plate-shaped sintered electrode was used. A test cell was assembled using the nickel electrode as a reference electrode. A 30 wt% potassium hydroxide aqueous solution was used as the electrolytic solution.

FIG. 1 is a schematic perspective view of the assembled test cell. The illustrated test cell 1 includes a disk-shaped paste electrode (test electrode; working electrode) 2 and an electrochemical capacity sufficiently larger than that of the test electrode. Cylindrical Sintered Nickel Electrode (Counter Electrode)
3, a plate-shaped sintered nickel electrode (reference electrode) 11, an insulating closed container (made of polypropylene) 4, and the like.

The sintered nickel electrode 3 is held by a positive electrode lead 5 connected to the upper surface 6 of the hermetically sealed container 4, and the paste electrode 2 is positioned perpendicular to the substantially center of the sintered nickel electrode 3 in the cylinder. Thus, it is held by the negative electrode lead 7 connected to the upper surface 6 of the closed container 4.

Each end of the positive electrode lead 5 and the negative electrode lead 7 penetrates the upper surface 6 of the closed container 4 and is exposed to the outside, and is connected to the positive electrode terminal 5a and the negative electrode terminal 7a, respectively.

The paste electrode 2 and the sintered nickel electrode 3 are immersed in an alkaline electrolyte (30% by weight potassium hydroxide aqueous solution; not shown) housed in a closed container 4,
The upper space of the alkaline electrolyte is filled with nitrogen gas so that a predetermined pressure is applied to the paste electrode 2.

Further, in the central portion of the upper surface 6 of the closed container 4,
In order to prevent the internal pressure of the closed container 4 from rising above a predetermined pressure, a pressure gauge 8 and a relief pipe 10 including a relief valve 9 are attached.

[Evaluation of Capacity Retention Ratio] Each test cell was charged at room temperature (25 ° C.) at 20 mA / g for 15 hours, rested for 1 hour, and then discharged at 20 mA / g to a discharge end voltage of 1.0 V. Then, a charge / discharge cycle test in which the step of resting for 1 hour was defined as one cycle, and the capacity retention rate (%) of each test electrode at the 100th cycle was obtained. Here, the capacity retention rate is a ratio to the maximum capacity (100%).

The relationship between the capacity retention rate of each test electrode obtained by the above-mentioned measurement and the value of the parameter P _A or P _B obtained for the hydrogen storage alloys AL1 to AL6 is shown in FIGS. 2 and 3, respectively. FIG. 2 is a graph in which the vertical axis shows the capacity retention rate obtained by actual measurement, and the horizontal axis shows the value of the parameter P _A of each hydrogen storage alloy. In FIG. 3, the vertical axis shows actual measurement. 6 is a graph showing the capacity retention rate and the value of the parameter P _B of each hydrogen storage alloy on the horizontal axis.

From FIGS. 2 and 3, there is a substantially linear (linear) correlation between the capacity retention obtained by actual measurement and the value of the parameter P _A or P _B for each hydrogen storage alloy. I understand that.

Therefore, in order to estimate the capacity retention rate of each test electrode from the value of the parameter P _A or P _B , the following method was used.

First, a calibration curve showing the correlation between each of the capacity maintenance ratios obtained by actual measurement of the test electrodes A1, A3 and A6 and the parameters P _A and P _B was obtained by the non-linear least square method. This calibration curve is shown by a solid line in FIGS. 2 and 3 above.

Next, from the above calibration curve, the test electrode A2,
The capacity retention rates of A4 and A5 were estimated, and this estimated capacity retention rate was compared with the capacity retention rate previously obtained by actual measurement. The estimated capacity retention rate was obtained as points on the calibration curve with the horizontal axis representing the value of P _A or P _B for hydrogen storage alloys AL2, AL4, and AL5, and as the vertical axis coordinates of these points. The results are shown in Table 2.

[0039]

[Table 2]

As shown in Table 2, the capacity maintenance rates of the test electrodes A2, A4 and A5 estimated from the calibration curve and the capacity maintenance rates of the respective test electrodes obtained by actual measurement are very close to each other. From this, it is understood that the capacity maintenance rate can be estimated with high accuracy by using the parameter P _A or P _B.

[Evaluation of Degree of Activation] For each test cell,
After charging for 15 hours at 20mA / g and resting for 1 hour, 1
The discharge capacity C ₁ when discharged to a discharge end voltage of 1.0 V at 00 mA / g and the discharge capacity C ₂ when discharged to a discharge end voltage of 1.0 V at 20 mA / g are obtained,
The activation degree (%) was determined from these discharge capacities C ₁ and C ₂ according to the following formula.

Activation degree = C ₁ / (C ₁ + C ₂ ) × 100 (F)

The relationship between the activation degree of each test electrode obtained by the above-mentioned actual measurement and the value of the parameter P _A or P _B previously obtained for the hydrogen storage alloys AL1 to AL6 is shown in FIGS. 4 and 5, respectively. . FIG. 4 is a graph in which the vertical axis represents the measured activation degree and the horizontal axis represents the value of the parameter P _A of each hydrogen storage alloy. In FIG. 5, the vertical axis represents the measured value. 6 is a graph showing the degree of activation and the value of the parameter P _B of each hydrogen storage alloy on the horizontal axis.

From FIGS. 4 and 5, the degree of activation obtained by actual measurement and the parameter P _A or P for each hydrogen storage alloy were obtained.
It can be seen that there is a substantially linear (linear) correlation with the value of _B.

Therefore, in order to estimate the activation degree of each test electrode from the value of the parameter P _A or P _B , the following method was used.

First, a calibration curve showing the correlation between each activation degree and the parameters P _A and P _B obtained by actually measuring the test electrodes A1, A3 and A6 was obtained by the non-linear least square method. This calibration curve is shown by a solid line in FIGS. 4 and 5 above.

Next, from the above calibration curve, the test electrode A2,
The activation degree of A4 and A5 was estimated, and this estimated activation degree was compared with the activation degree previously obtained by actual measurement. The estimated activation degree was obtained as a vertical axis coordinate of a point on the calibration curve with the horizontal axis representing the value of P _A or P _B for the hydrogen storage alloys AL2, AL4 and AL5. The results are shown in Table 3.

[0048]

[Table 3]

As shown in Table 3, the activation degrees of the test electrodes A2, A4 and A5 estimated from the calibration curve and the activation degrees of these test electrodes obtained by actual measurement are very close to each other. From this, it is understood that the activation degree can be estimated with high accuracy by using the parameter P _A or P _B.

(Example 2) [Preparation of hydrogen storage alloy] Ti, Zr, Ni, Co, V and Mn were added in an element ratio of 0.5: 0.5: 1.0: 0.2: 0.
After weighing and mixing at 5: 0.3, arc melting was performed in an argon gas atmosphere. Next, the molten alloy obtained by arc melting was 1 × 10 ³ cm / sec, 2 × 10 ³ cm
/ Sec, 3 × 10 ³ cm / sec, 4 × 10 ³ cm /
sec, 5 × 10 ³ cm / sec or 6 × 10 ³ cm /
It is dropped onto a roll that rotates at high speed at each peripheral speed of sec to solidify (liquid quenching method), and the composition formula Ti _0.5 Zr _0.5
Hydrogen storage alloy A represented by NiCo _0.2 V _0.5 Mn _0.3
L7 to AL12 were obtained.

[Calculation of Parameters P _A and P _B ] From the X-ray diffraction patterns of the above hydrogen storage alloys AL7 to AL12 and the reference X-ray diffraction pattern of the hydrogen storage alloys, the hydrogen storage alloys AL7 to AL12 and the selective orientation are selected. Of various lattice planes (h ₁ k ₁ l
₁ ) planes _, (h ₂ k ₂ l ₂ ) planes _, ..., (h _X k _X l _X ) planes are calculated, and these integrated intensity ratios are calculated as I _(hkl) in the above equation (E _). / I _{s (hkl)} , the selective orientation planes (002) planes of the hydrogen storage alloys AL7 to AL12 and the respective lattice planes (h ₁ k ₁ l ₁ ) planes _, (h ₂ k ₂ l ₂ ) planes _, ..., ( h _X
k _X l angle phi ₁ and _X) plane, φ _2, ..., φ _X substituted in phi in the formula (E) the relevant parameter values to the selected orientation of each of the hydrogen absorbing alloy (alloy structure) P _A and P _B were determined using the nonlinear least squares method. The results are shown in Table 4.

[0052]

[Table 4]

[Evaluation of Capacity Maintenance Rate] The above hydrogen storage alloy A
A test cell was assembled in the same manner as in Example 1 except that L7 to AL12 were used as test electrodes, and a charge / discharge cycle test was performed on each test cell to determine the capacity retention rate (%) of each test electrode at the 100th cycle. I asked. The charge / discharge cycle test of each test cell was performed under the same conditions as the charge / discharge cycle conditions of Example 1.

The relationship between the capacity retention rate of each test electrode obtained by the above-mentioned actual measurement and the value of the parameter P _A or P _B obtained for the hydrogen storage alloys AL7 to AL12 is shown in FIG.
7 and FIG. 6, the capacity retention rate was determined by actual measurement on the vertical axis, also the horizontal axis of each of the hydrogen absorbing alloy parameter P _A
7 is a graph in which the vertical axis represents the capacity retention rate obtained by actual measurement, and the horizontal axis represents the value of the parameter P _B of each hydrogen storage alloy.

From FIGS. 6 and 7, there is a substantially linear (linear) correlation between the capacity retention obtained by actual measurement and the value of the parameter P _A or P _B for each hydrogen storage alloy. I understand.

Therefore, in order to estimate the capacity retention rate of each test electrode from the value of the parameter P _A or P _B , the following method was used.

First, each capacity maintenance ratio and the parameters P _A and P _B obtained by the actual measurement of the test electrodes A7, A9 and A12.
The calibration curve showing the correlation with was obtained by the nonlinear least squares method. This calibration curve is shown by a solid line in FIGS. 6 and 7 above.

Next, from the above calibration curve, test electrode A7,
The capacity retention rates of A9 and A12 were estimated, and this estimated capacity retention rate was compared with the capacity retention rate previously obtained by actual measurement. The estimated capacity retention rate was obtained by obtaining a point on the calibration curve having the value of P _A or P _B for the hydrogen storage alloys AL7, AL9, and AL12 as the abscissa, and the ordinate of this point. The results are shown in Table 5.

[0059]

[Table 5]

As shown in Table 5, the capacity retention rates of the test electrodes A7, A9 and A12 estimated from the calibration curve and the capacity retention rates of these test electrodes obtained by actual measurement are very similar. From this, it is understood that the capacity maintenance rate can be estimated with high accuracy by using the parameter P _A or P _B.

[Evaluation of degree of activation] The degree of activation (%) of each test electrode was determined in the same manner as in Example 1. Charging / discharging of each test cell was performed under the same charging / discharging conditions when the activation degree was evaluated in Example 1.

The relationship between the activation degree of each test electrode obtained by the above actual measurement and the value of the parameter P _A or P _B obtained for the hydrogen storage alloys AL7 to AL12 is shown in FIGS. 8 and 9, respectively. FIG. 8 is a graph in which the ordinate represents the measured activation degree and the abscissa represents the value of the parameter P _A of each hydrogen storage alloy. In FIG. 9, the ordinate represents the measured value. 6 is a graph showing the degree of activation and the value of the parameter P _B of each hydrogen storage alloy on the horizontal axis.

From FIGS. 8 and 9, the degree of activation obtained by actual measurement and the parameter P _A or P for each hydrogen storage alloy
It can be seen that there is a substantially linear (linear) correlation with the value of _B.

Therefore, in order to estimate the activation degree of each test electrode from the value of the parameter P _A or P _B , the following method was used.

First, a calibration curve showing the correlation between the parameters P _A and P _B and the respective degrees of activation obtained by actually measuring the test electrodes A7, A9 and A12 was obtained by the non-linear least squares method. This calibration curve is shown by a solid line in FIGS. 8 and 9 above.

Then, from the above calibration curve, the test electrode A8,
The activation degree of A10 and A11 was estimated, and this estimated activation degree was compared with the activation degree previously obtained by actual measurement.
Estimated activation degree is hydrogen storage alloys AL8, AL10 and A
_A point having the value of P _A or P _B for L11 as the abscissa coordinate was obtained on the calibration curve and obtained as the ordinate coordinate of this point. The results are shown in Table 6.

[0067]

[Table 6]

As shown in Table 6, the activation degrees of the test electrodes A8, A10 and A11 estimated from the calibration curve and the activation degrees of the test electrodes obtained by actual measurement are very close to each other. From this, it is understood that the activation degree can be estimated with high accuracy by using the parameter P _A or P _B.

As shown in Examples 1 and 2, for the same alloy composition, it is possible to estimate the electrode characteristics of each hydrogen storage alloy using a common calibration curve. If the value changes, it is necessary to create a new calibration curve for the alloy and evaluate it.

In the above examples, MmNi _3.1 Co _0.9 Mn _0.6 Al _0.4 was selected as the hydrogen storage alloy to be evaluated.
And Ti _0.5 Zr _0.5 NiCo _0.2 V _0.5 Mn _0.3 have been described as an example, but the present invention does not particularly limit the kind of the hydrogen storage alloy.

Further, in the above-mentioned examples, the case where the present invention is applied to the evaluation of the capacity retention rate and the activation degree was described as a specific example, but the present invention is not limited to the corrosion resistance of the alloy, the initial capacity and the like. It can be suitably applied to evaluation of electrode characteristics.

Furthermore, in the above embodiment, F (φ) =
As a function F (φ) that satisfies I _(hkl) / I _{s (hkl)} , P
_A + (1-P _A ) exp (-P _B · φ ² ) was used,
Any function can be used without particular limitation as long as it is a function that can determine the electrode characteristics with high accuracy through specific parameters.

[0073]

The electrode characteristics of the hydrogen storage alloy can be evaluated quickly.

[Brief description of drawings]

FIG. 1 is a perspective view of a test cell assembled in an example.

FIG. 2 is a graph showing a relationship between a parameter P _A and a capacity maintenance rate.

FIG. 3 is a graph showing a relationship between a parameter P _B and a capacity retention rate.

FIG. 4 is a graph showing the relationship between the parameter P _A and the degree of activation.

FIG. 5 is a graph showing the relationship between the parameter P _B and the degree of activation.

FIG. 6 is a graph showing a relationship between a parameter P _A and a capacity retention rate.

FIG. 7 is a graph showing a relationship between a parameter P _B and a capacity retention rate.

FIG. 8 is a graph showing the relationship between the parameter P _A and the degree of activation.

FIG. 9 is a graph showing the relationship between the parameter P _B and the degree of activation.

─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] December 15, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0019

[Correction method] Change

[Correction content]

The AB ₂ type hexagonal structure or cubic
As the component A of the hydrogen storage alloy having a crystal structure , Ti,
Zr, Cr, V, and one or more elements selected from alkaline earth metal elements such as Ca and Mg are exemplified. As the B component, Cr, Mn, Fe, Co, Ni,
One or more kinds of transition elements selected from Cu, Sn, Al, etc. are exemplified.

 ─────────────────────────────────────────────────── (72) Inventor Hiroshi Nakamura 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Yumiko Nakamura 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. Incorporated (72) Inventor Ikuro Yonezu 2-18 Keihan Hondori, Moriguchi City, Osaka Sanyo Electric Co., Ltd.

Claims (5)

[Claims] 1. A plurality of calibrations having different orientations in a lattice plane (h.k.l.) and having the same alloy composition as the hydrogen storage alloy E to be evaluated and having a selective orientation. line creation hydrogen storage alloy M _1, M _2, ..., the value of the parameter P of the function F (phi) in satisfying the following formula (a) for the M _X P
_1, P _2, ..., a P _X, the calibration curve for the hydrogen storage alloy _{M 1, M 2, ...,} M X and, between the hydrogen-absorbing alloy S as a reference, arbitrarily selected grid plane (h ₁ k ₁ l ₁ ) plane, (h ₂
The integrated intensity ratio I _{M1 (h1k1l1)} / I _{s (h1k1l1)} , I of the X-ray diffraction peaks in the (k ₂ l ₂ ) plane, ..., (h _X k _X l _X ) plane
_{M2 (h2k2l2)} / I _{s (h2k2l2)} , ..., I _{MX (hXkXlX)} / I
_{s (hXkXlX)} and the lattice plane (h ₁ k ₁ l ₁ ) plane,
, (H ₂ k ₂ l ₂ ) planes, ..., (h _x k _x l _x ) planes and the lattice planes (h.k.l.) planes φ ₁ , φ ₂ , ..., φ
Step (1), which is obtained by substituting _X into I _(hkl) / I _{s (hkl)} and φ in the following formula (A), the P ₁ , P ₂ , ... _, P _x, and the calibration. line creation hydrogen storage alloy M _1, M _2, ..., Found T _1, T ₂ representing the characteristic of the electrode material M _{X, ...,} creating a calibration curve showing a correspondence between T _X (2) And a value P _{E of the} parameter P for the hydrogen storage alloy E to be evaluated, the lattice plane (h) of the hydrogen storage alloy E to be evaluated and the reference hydrogen storage alloy S _E1 k _E1 l _E1 ) plane, (h _E2 k _E2 l _E2 ) plane, ..., (h
_EY k _EY l _EY ) X-ray diffraction peak integrated intensity ratio I
_{E1 (hE1KE1lE1)} / _{Is (hE1kE1lE1)} , _{IE2 (hE2KE2lE2)} /
I _{s (hE2kE2lE2)} ,…, I _{EY (hEYKEYlEY)} / I
_{s (hEYkEYlEY)} and the lattice plane (h _E1 k _E1 l _E1 ) plane,
, (H _E2 k _E2 l _E2 ) planes, ..., (h _EY k _EY l _EY ) planes and the lattice planes (h.k.l.) planes φ _E1 , φ _E2 , ..., φ
_EY is substituted into I _(hkl) / I _{s (hkl)} and φ in the following formula (A) to obtain (3), and the P _E is compared with the calibration curve to perform the evaluation. A method for evaluating a hydrogen storage alloy for an electrode, which comprises the step (4) of estimating the characteristics of the hydrogen storage alloy E to be an electrode material. F (φ) = I _(hkl) / I _{s (hkl)} (A) [wherein I _(hkl) is the hydrogen storage alloys M ₁ and M ₂ for creating the calibration curve on the lattice plane (hkl) plane] , M _X or the integrated intensity of the X-ray diffraction peak of the hydrogen storage alloy E to be evaluated; I _{s (hkl)} is the X-ray diffraction peak of the reference hydrogen storage alloy S on the lattice plane (hkl) plane. F (φ) is the hydrogen storage alloy M ₁ for preparing the calibration curve,
M _2, ..., varies in response to the alloy structure of the M _X or said to be evaluated hydrogen storage alloy E, a function of φ having a parameter P which determines the properties as those of the electrode material unambiguously;
φ is the lattice plane (h.k.l.) plane and the lattice plane (hk.l)
l) The angle formed by the plane (unit: radian). ] 2. The method for evaluating a hydrogen storage alloy for an electrode according to claim 1, wherein a function of φ specified by the following formula (B) is used as the F (φ). F (φ) = P _A + (1-P _A ) exp (−P _B · φ ² ) ... (B) [wherein, P _A and P _B are the hydrogen storage alloy M ₁ for preparing the calibration curve, , M _X and M ₂ and the parameters that change corresponding to the alloy structure of the hydrogen storage alloy E to be evaluated and uniquely determine the characteristics of these as the electrode material. Corresponding thing: φ is an angle (unit: radian) formed by the lattice plane (h.k.l.) plane and the lattice plane (hkl) plane. ] 3. The lattice planes (h _E1 k _E1 l _E1 ) planes, (h _E2 k
_E2 l _E2 ), ..., (h _EY k _EY l _EY ) all or part of the lattice planes is the lattice plane (h ₁ k ₁ l ₁ ) plane,
The method for evaluating a hydrogen storage alloy for an electrode according to claim 1 or 2, wherein the lattice plane is the same as the (h ₂ k ₂ l ₂ ) plane, ..., (h _X k _X l _X ) plane. 4. The P ₁ , P in the step (1)
_2. Each value of ₂ , ..., P _X is obtained by the least square method.
Alternatively, the method for evaluating a hydrogen storage alloy for an electrode according to item 2. 5. The method for evaluating a hydrogen storage alloy for an electrode according to claim 1, wherein the value of P _E in step (3) is determined by a least squares method.