JP3737163B2 - Rare earth metal-nickel hydrogen storage alloy and negative electrode for nickel metal hydride secondary battery - Google Patents

Description

【００４０】
【表２】

【図面の簡単な説明】
【図１】図１は、実施例１で調製した帯状鋳塊の結晶粒内に含まれている逆位相境界の存在量を測定するための高分解能透過電子顕微鏡写真（図２のＢで示す領域の拡大図）である。
【図２】図２は、実施例１で調製した帯状鋳塊の、逆位相境界が存在する結晶粒の存在割合を測定するための高分解能透過電子顕微鏡写真である。
【符号の説明】
Ａ：逆位相境界[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a rare earth metal-nickel-based hydrogen storage alloy that exhibits a high capacity and a long life by being used as a hydrogen storage container, a heat pump, a negative electrode material of a nickel metal hydride secondary battery, etc. The present invention relates to a negative electrode for a secondary battery.
[0002]
[Prior art]
As negative electrode alloys of nickel-metal hydride secondary batteries currently produced in large quantities, Mm (Misch metal), Ni, Co, Mn, and Al-based AB ₅ type alloys are mainly used. This alloy has the characteristics that the hydrogen storage amount is larger than that of other alloys, and the hydrogen absorption / release pressure at normal temperature is 1 to 5 atm, which makes it easy to use.
However, the conventional AB ₅ type rare earth metal-nickel alloy has low initial activity during hydrogen storage, and in order to obtain 100% hydrogen storage, hydrogen is absorbed and released several times to several tens of times in the initial stage. There must be. In addition, since this alloy expands and contracts due to absorption and release of hydrogen, there is a disadvantage that cracks occur and the powder is pulverized to deteriorate the battery characteristics.
[0003]
Recently, an electrode having a higher battery capacity has been desired, and in order to increase the battery capacity, AB ₂ type, AB having a composition in which the content of transition metal containing nickel as a main component is reduced with respect to rare earth metals. Type ₃ and A ₂ B ₇ type alloys have been studied. However, these alloys have an increased amount of hydrogen occlusion, but when they absorb hydrogen, they become amorphous and the hydrogen release temperature rises. At room temperature, there is a possibility that hydrogen is not released and cannot be used.
[0004]
As described above, it is desired that the rare earth metal-nickel-based hydrogen storage alloy used for the negative electrode material of the conventional nickel-metal hydride secondary battery has a higher capacity and a longer life.
However, for example, a method of increasing the proportion of Co or the like in order to extend the life, a method of eliminating the composition segregation by heat-treating the alloy itself, and removing strain at the time of casting have been proposed. The capacity decreases, while on the other hand, increasing the proportion of Mn to increase the capacity sacrifices longer life. Therefore, the fact is that there is no known alloy that satisfies all of the initial high activation, high battery capacity, and long life at the same time.
[0005]
As described above, the composition of the nickel-hydrogen secondary battery such as the conventional AB ₅ type structure is mostly studied, but the characteristics of the alloy also affect the finer crystal state and crystal distribution. . Therefore, in recent years, attention has been paid to how such a crystalline state affects the alloy characteristics.
[0006]
By the way, it is known that the Ce ₂ Ni ₇ structure and the CeNi ₃ structure have an antiphase boundary. This antiphase boundary is a boundary between the positive phase and the antiphase in a region called an antiphase region where the atomic arrangement on the sublattice is reversed in a superlattice structure in which the arrangement of component atoms is incomplete. It is a surface. (See pages 439-440, “Physics Dictionary Reprinted (issued October 20, 1986)” issued by Baifukan Co., Ltd.).
However, such antiphase boundary effects are not known. Therefore, it has not been known at all to apply this structure in order to improve the performance of the hydrogen storage alloy.
[0007]
[Problems to be solved by the invention]
The object of the present invention is to simultaneously improve all of the initial activity, battery capacity and life as compared to hydrogen storage alloys, particularly rare earth metal-nickel hydrogen storage alloys that can be used as negative electrode materials for conventional nickel hydrogen secondary batteries. It is an object of the present invention to provide a rare earth metal-nickel-based hydrogen storage alloy and a method for producing the same.
Another object of the present invention is to provide a negative electrode for a nickel-metal hydride secondary battery that has all of initial high activation, high battery capacity, and long life at the same time.
[0008]
[Means for Solving the Problems]
According to the present invention, the following general formula (1)
(R _1-X L _X ) (Ni _{1- y My} ) _Z (1)
(In the formula, R represents two or more mixed elements of La and at least one of Ce, Pr, and Nd , and L represents Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc. , Mg, Ca, Ti, Zr, or a mixed element thereof, and M is Co, Al, Mn, Fe, Cu, Mo , Si, V, Cr, Nb, Hf, Ta, W, B, C, or These mixed elements are represented by a composition represented by 0.2 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5, and 2.0 ≦ z <3.0 (hereinafter referred to as composition A). 50% or more and less than 95% by volume of crystals containing 20 or more and less than 40 anti-phase boundaries perpendicular to the C axis of the crystal grains in the alloy per 20 nm in the C axis direction. In addition, the element represented by L in the general formula (1) is disposed in the reverse phase region in an amount of 60% or more and less than 95% of the addition amount. A rare earth metal-nickel based hydrogen storage alloy (hereinafter referred to as hydrogen storage alloy B) is provided.
According to the present invention, hydrogen storage alloy B and a negative electrode for a nickel-hydrogen battery including a conductive agent as the negative electrode material is provided.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
The inventor of the present invention has been able to withstand use because the alloy of LaNi ₂ type structure absorbs hydrogen conventionally, but becomes amorphous and the hydrogen release temperature increases, and the hydrogen release amount decreases at room temperature. As shown in the composition A represented by the general formula (1), a part of the rare earth metal element is substituted with a specific element (L) (hereinafter referred to as a substitution element L), and a specific antiphase boundary region It has been found that the hydrogen storage alloy B having the above property prevents amorphization and has a positive effect on the initial activation. The existence of such an antiphase boundary has a positive effect on the hydrogen storage capacity because the substitution element L is present in the antiphase region in an amount of 60% or more of the addition amount, and the rare earth element and the substitution element are facing the antiphase boundary. This is probably because the elements L are arranged and hydrogen can easily move through this boundary.
[0010]
The hydrogen storage alloy B of the present invention has the composition A represented by the general formula (1), and there are 20 or more antiphase boundaries present perpendicular to the C axis of crystal grains in the alloy per 20 nm in the C axis direction. , Rare earth metal-nickel-based hydrogen occlusion in which less than 40 crystals are contained in an amount of 50 volume% or more and less than 95 volume%, and 60% or more and less than 95% of the element represented by the substitution element L is disposed in the reverse phase region. It is an alloy. When the content of the crystal containing 20 or more and less than 40 antiphase boundaries perpendicular to the C axis of the crystal grains in the C axis direction per 20 nm is less than 50% by volume, the initial activity is lowered. . On the other hand, when it is 95% by volume or more, the battery life is reduced. Further, when the substitution element L is less than 60% in the reverse phase region, it becomes amorphous when hydrogen is occluded, the hydrogen release temperature rises, hydrogen is not released at room temperature, and cannot be used. On the other hand, if it exceeds 95%, the hydrogen storage capacity decreases.
[0011]
The measurement of the antiphase boundary is performed using a high-resolution transmission electron microscope with an acceleration voltage of 200 kV or higher, and an electron beam is incident from the [100] axis of the alloy crystal grain, and a high-resolution image of the (100) plane at a magnification of 300,000 times or more. Can be obtained by measuring the number of antiphase boundaries per unit length in the C-axis direction ([001] direction). In addition, the measurement of the abundance of crystal grains containing an antiphase boundary is performed by using a transmission electron microscope having an acceleration voltage of 200 kV or higher at a magnification of 10,000 to 50,000 times and a transmission electron microscope image of the (100) plane of the crystal grains. And measuring the area ratio of the crystal containing the antiphase boundary. The abundance of the substitution element L substituted in the antiphase region can be obtained by performing composition analysis in the antiphase region with a beam diameter of 4 nm using an EDX analyzer of a field emission high resolution transmission electron microscope.
[0012]
When the atomic ratio of (Ni _{1- y My} ) is less than 1.8 when z in the general formula (1), that is, (R _1-x L _x ) is 1, the antiphase boundary is It does not exist and cannot be used due to phase decomposition during hydrogen storage. On the other hand, when it is 3.0 or more, the hydrogen storage amount decreases. In the general formula (1), when y, that is, the atomic ratio of the substitution element M substituted for Ni exceeds 0.5, the surface activity is lowered and the hydrogen storage amount is lowered. In the general formula (1), x, that is, when the atomic ratio of the substitution element L to be substituted with R exceeds 0.6, the hydrogen storage amount decreases, and the battery capacity is reduced when the negative electrode for a nickel metal hydride secondary battery is obtained. descend.
[0013]
In the composition A, R in the formula can be selected from one or more of La, Ce, Pr, and Nd rare earth metals. In the case of combining two or more kinds, the content ratio of each element can be suitably selected so that it is preferably La 20 to 60 atomic%, Ce 0 to 60 atomic%, Pr 0 to 50 atomic%, and Nd 0 to 50 atomic%. Misch metal can also be used as a raw material. In the formula, the substitution element L that substitutes for the rare earth metal of R preferably has an atomic radius close to that of the rare earth metal, and is substituted for the site of the rare earth metal. Substitution element L is selected from heavy rare earth metals Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and other metals Y, Sc, Mg, Ca, Ti, Zr. Actually, in the hydrogen storage alloy B, the L element may be one kind or a mixture of two or more kinds. Among these substitution elements L, those having a large hydrogen storage amount alone are preferable. In the hydrogen storage alloy B of the present invention, these substitution elements L are not present alone, but are used as substitution elements for the rare earth metal R, even if the hydrogen storage amount alone is large, This is because defects such as pulverization due to occlusion occur. Therefore, in the hydrogen storage alloy B of the present invention, by replacing the rare earth metal R with the rare earth metal R, such defects can be complemented and an alloy exhibiting a positive effect by antiphase boundary precipitation can be obtained. The blending ratio (x in the formula) of such a substitution element L is 0.2 ≦ x ≦ 0.6, preferably 0.3 ≦ x ≦ 0.55, particularly preferably 0.45 ≦ x ≦ 0.55. It is.
[0014]
In addition, the metal related to M in the formula may be one kind or a combination of two or more kinds. The combination of two or more metals can be appropriately performed based on the properties of each metal. Specifically, Co has an action of expanding the crystal lattice to lower the equilibrium hydrogen pressure and an action of preventing pulverization and improving the life. The blending ratio is represented by y in the formula, that is, the atomic ratio of M when (Ni + M) is 1 (same basis for the following elements), preferably 0.01 to 0.3 atomic ratio, particularly preferably It is 0.02-0.2 atomic ratio. Al has the effect of expanding the crystal lattice to lower the equilibrium hydrogen pressure and the effect of increasing the hydrogen storage capacity. The blending amount is preferably 0.03 to 0.3 atomic ratio, particularly preferably 0.05 to 0.1 atomic ratio. Mn has the effect of expanding the crystal lattice to lower the equilibrium hydrogen pressure and the effect of increasing the hydrogen storage capacity. The blending amount is preferably 0.03 to 0.3 atomic ratio, particularly preferably 0.05 to 0.2 atomic ratio. Fe has the effect of activating the alloy surface and increasing the rate of hydrogen absorption and release. The blending amount is preferably 0.03 atomic ratio or less, particularly preferably 0.01 to 0.02 atomic ratio. Cu has the effect of expanding the crystal lattice and lowering the equilibrium hydrogen pressure. The blending amount is preferably 0.01 to 0.3 atomic ratio, particularly preferably 0.02 to 0.2 atomic ratio. Zr has the effect of improving the hysteresis characteristic of the PCT curve (hydrogen dissociation pressure-composition isotherm) and the effect of precipitating at the grain boundary to prevent cracking and improving the life. The blending amount is preferably 0.1 atomic ratio or less, and particularly preferably 0.01 to 0.03 atomic ratio. Ti has the effect of improving the hysteresis characteristics of the PCT curve. The blending amount is preferably 0.1 atomic ratio or less, and particularly preferably 0.01 to 0.03 atomic ratio. Mo has the effect of increasing the activity and increasing the hydrogen absorption / release rate. The blending amount is preferably 0.05 atomic ratio or less, particularly preferably 0.01 to 0.02 atomic ratio. Si has the effect of lowering the equilibrium hydrogen pressure. The blending amount is preferably 0.01 to 0.25 atomic ratio, particularly preferably 0.02 to 0.05 atomic ratio. V has an effect of easily generating an antiphase boundary. The blending amount is preferably 0.01 to 0.2 atomic ratio, particularly preferably 0.02 to 0.05 atomic ratio. Cr has a crack preventing effect. The blending amount is preferably 0.01 to 0.2 atomic ratio, particularly preferably 0.03 to 0.1 atomic ratio. Nb has a crack preventing effect. The blending amount is preferably 0.01 to 0.05 atomic ratio, particularly preferably 0.02 to 0.04 atomic ratio. Hf has the effect of improving the hysteresis characteristics. The blending amount is preferably 0.05 atomic ratio or less, particularly preferably 0.01 to 0.03 atomic ratio. Ta has the effect of improving the hysteresis characteristics. The blending amount is preferably 0.01 to 0.05 atomic ratio, particularly preferably 0.02 to 0.03 atomic ratio. W has the effect of increasing the activity and increasing the hydrogen absorption / release rate. The blending amount is preferably 0.05 atomic ratio or less, particularly preferably 0.01 to 0.03 atomic ratio. B has the effect of increasing the activity and increasing the hydrogen absorption / release rate. The blending amount is preferably 0.03 atomic ratio or less, particularly preferably 0.01 to 0.02 atomic ratio. C has the effect of increasing the hydrogen absorption / release rate. The blending amount is preferably 0.03 atomic ratio or less, particularly preferably 0.01 to 0.02 atomic ratio.
[0015]
The hydrogen storage alloy B of the present invention may contain impurities inevitably contained in each raw material component of the composition A or during the production of the hydrogen storage alloy B.
[0016]
Specific examples of the composition A represented by the general formula (1) include the following alloy compositions.
[0017]
La _0.16 Ce _0.32 Pr _0.03 Nd _0.13 Gd _0.25 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.16 Ce _0.32 Pr _0.03 Nd _0.13 Gd _0.35 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Gd _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Dy _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Er _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Yb _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Y _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Sc _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Mg _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Ca _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Ti _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Zr _0.5 Ni _1.5 Al _0.09 Co _0.2 Mn _0.2 Fe _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Gd _0.5 Ni _1.5 Al _0.07 Co _0.2 Mn _0.2 Fe _0.02 B _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Gd _0.5 Ni _1.5 Al _0.07 Co _0.2 Mn _0.2 Fe _0.02 Mo _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Gd _0.5 Ni _1.5 Al _0.07 Co _0.2 Mn _0.2 Fe _0.02 W _0.02 ,
La _0.12 Ce _0.25 Pr _0.03 Nd _0.1 Gd _0.5 Ni _1.5 Al _0.07 Co _0.2 Mn _0.2 Fe _0.02 Cu _0.02
[0018]
In the method for producing the hydrogen storage alloy B of the present invention, the raw material metal blended so as to have the composition A is first melted, and the melt is subcooled to 50 to 500 ° C., and the cooling rate is 1000 to 10000 ° C./second, preferably Is uniformly solidified under cooling conditions of 3000 to 10000 ° C./second. In this case, the degree of supercooling is a value of (melting point of alloy) − (actual temperature of alloy melt below melting point). More specifically, “undercooling” refers to a temperature at which solidification does not actually occur even when the alloy melt is cooled and reaches the melting point of the alloy, and further decreases, and when the nucleation temperature is reached, the alloy melt This is a phenomenon in which a solid phase, that is, a crystal is formed and solidification occurs for the first time. Such supercooling degree control can be performed, for example, by controlling the temperature of the alloy melt prepared using a crucible or the like, and by appropriately adjusting the time and speed until it leads to a single roll for solidification. it can. When the degree of supercooling and the cooling rate are outside the essential temperature range, an ingot having a composition capable of depositing a desired antiphase boundary cannot be obtained.
The raw metal can be melted by, for example, a vacuum melting method, a high-frequency melting method, or the like, preferably using a crucible or the like in an inert gas atmosphere or the like. The treatment based on the degree of supercooling and the cooling rate can be carried out, for example, by a method in which an alloy melt is preferably continuously fed and solidified on a single roll, a twin roll or a disk. In particular, when solidifying by the roll method, the casting temperature and the pouring speed are appropriately selected so that the thickness of the resulting alloy ingot is in the range of 0.1 to 20 mm, and the degree of supercooling and cooling rate are selected. It is the easiest method to process so that
[0019]
Next, in the production method of the present invention, the obtained alloy ingot is vacuum or in an inert atmosphere at a temperature of 600 to 750 ° C., preferably 650 to 730 ° C., for 0.1 to 12 hours, preferably 4 The hydrogen storage alloy B can be prepared by heat treatment for ˜8 hours to precipitate a desired antiphase boundary. Under conditions other than the conditions for the essential heat treatment, a tissue having a desired antiphase boundary cannot be obtained. The control temperature of such heat treatment is preferably within ± 10 ° C., and can be performed by a normal heat treatment furnace or the like. The alloy ingot to be subjected to the heat treatment can be heat-treated as a coarsely crushed piece, a pulverized powder or the like even if it is in a shape as it is. The alloy ingot after the heat treatment can be made into a hydrogen storage alloy powder by ordinary pulverization and fine pulverization processes.
[0020]
By this method, crystals containing 20 or more and less than 40 antiphase boundaries in the direction perpendicular to the C-axis of the crystal grains in the direction of the C-axis and 20 nm or less are contained in an amount of 50 to 95 vol%. It is possible to prepare a rare earth metal-nickel-based hydrogen storage alloy B in which the substitution element L shown in FIG. 5 is disposed in the antiphase region by 60% or more and less than 95% of the addition amount of the substitution element L.
[0021]
The negative electrode for a nickel metal hydride secondary battery of the present invention contains the hydrogen storage alloy B and a conductive agent as negative electrode materials.
[0022]
The hydrogen storage alloy B is preferably used as a pulverized product, and the pulverized particle size is preferably 20 to 100 μm, and particularly preferably a uniform particle size of 40 to 50 μm. This pulverization can be performed, for example, by roughly pulverizing the alloy with a stamp mill or the like and then mechanically pulverizing the alloy in a non-oxidizing solvent such as hexane using an apparatus such as a planetary ball mill. The content of the alloy is preferably 70 to 95% by weight, particularly 80 to 90% by weight, based on the total amount of the negative electrode material. If it is less than 70% by weight, the amount of hydrogen occluded in the obtained negative electrode is lowered, and it is difficult to achieve high capacity, which is not preferable. On the other hand, if it exceeds 95% by weight, the conductivity is lowered and the durability is also deteriorated.
[0023]
Examples of the conductive agent include copper, nickel, cobalt, carbon, and the like. In use, the conductive agent can be used as a powder having a particle size of about 1 to 10 μm. The content of the conductive agent is preferably 5 to 20% by weight, particularly preferably 10 to 20% by weight, based on the total amount of the negative electrode material.
[0024]
In addition to the above essential components, the negative electrode for a nickel metal hydride secondary battery of the present invention can contain a binder. Preferred examples of the binder include 4-fluoroethylene-6-fluoropropylene copolymer (FEP), polytetrafluoroethylene, carboxymethyl cellulose, and the like. The content ratio of the binder is preferably less than 10% by weight with respect to the total amount of the negative electrode material.
[0025]
In order to prepare the negative electrode for a nickel metal hydride secondary battery of the present invention, for example, the negative electrode material is applied to a current collecting substrate such as nickel mesh, nickel or copper expanded metal, nickel or copper punching metal, foamed nickel, woolen nickel or the like. It can be obtained by a method of binding molding. The binder molding can be performed by a roll press method, a molding press method, or the like, and the shape is preferably binder-molded into a sheet shape or a pellet shape. The obtained negative electrode can be used in the same manner as a normal nickel-hydrogen secondary battery negative electrode to form a secondary battery.
[0026]
【The invention's effect】
The hydrogen storage alloy B of the present invention has a specific composition, and contains 50 or more vol% of crystals containing 20 or more and less than 40 antiphase boundaries perpendicular to the C axis of the crystal grains per 20 nm in the C axis direction. , And the substitutional element L has a structure in which the substitution element L is substituted in the reverse phase region by 60% or more and less than 95%, so that it has an initial high activity and high electricity when used as a negative electrode material for a nickel metal hydride secondary battery. All of capacity and long life can be exhibited at the same time. Moreover, in the manufacturing method of this invention, such a hydrogen storage alloy B can be obtained reasonably by the specific heat processing which controlled supercooling degree and cooling rate, and controlled temperature and time.
[0027]
Moreover, since the negative electrode for nickel metal hydride secondary batteries of the present invention exhibits all of initial high activity, high electric capacity, and long life at the same time, demand for replacing the conventional negative electrode can be expected.
[0028]
【Example】
EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention in detail, this invention is not limited to these.
[0029]
[Example 1]
La 9.1 parts by weight, Ce 18.4 parts by weight, Pr 1.7 parts by weight, Nd 7.7 parts by weight, Gd 16.1 parts by weight, Ni 36.0 parts by weight, Al 1.0 part by weight, Co 4.8 parts by weight, Mn 4. The raw materials were prepared so as to be 5 parts by weight and 0.5 parts by weight of Fe, and melted in an argon atmosphere in a high frequency induction melting furnace to obtain an alloy melt. Subsequently, this alloy melt is manufactured into a strip-shaped alloy ingot having a thickness of 0.3 to 0.4 mm using a single roll casting apparatus under conditions of a supercooling degree of 150 ° C. and a cooling rate of 2000 to 5000 ° C./second. did. The obtained alloy ingot was heat-treated at 700 ° C. for 4 hours in an argon atmosphere. Table 1 shows the obtained alloy ingot composition converted into an atomic ratio.
[0030]
The heat-treated alloy ingot is observed per 20 nm of the antiphase boundary existing perpendicular to the C axis of the crystal grain by observing the (100) plane of the crystal grain using a high resolution transmission electron microscope (JEL4000EX) manufactured by JEOL. And the ratio of the crystal grains having the antiphase boundary contained in the alloy. Moreover, the abundance with respect to the addition amount of the substitution element L of the general formula (1) existing in the antiphase region was determined by a high resolution EDX analysis method. The results are shown in Table 2. Further, FIG. 1 shows a micrograph used for measuring the number of anti-phase boundaries present per 20 nm perpendicular to the C-axis of the crystal grains, and the proportion of the crystal grains having the anti-phase boundaries is measured. A photomicrograph used for this purpose is shown in FIG.
[0031]
Subsequently, this ingot was subjected to hydrogen occlusion in accordance with JIS H7201 (1991) “Method for measuring pressure-composition isotherm (PCT line) of hydrogen storage alloy” using an automatic high-pressure Siebelz apparatus for PCT measurement (manufactured by Reska). The amount and the hydrogen storage pressure were measured. The results are shown in Table 2.
[0032]
Next, the ingot was coarsely pulverized with a stamp mill, and then pulverized to an average particle size of 80 μm with a planetary ball mill in a hexane solvent. 10 g of the obtained powder, 1 g of copper powder as a conductive agent, and 0.3 g of FEP powder (tetrafluoroethylene-6fluoropropylene copolymer) as a binder are mixed to produce a pellet electrode having a diameter of 20 mm. did. This electrode was immersed in a 6N KOH solution, a battery was constructed using a mercury oxide reference electrode, and electrode characteristics were measured with a potention galvanostat (manufactured by Hokuto Denko). The results are shown in Table 2.
[0033]
The initial activity and the battery life were measured based on the time when the battery capacity reached a steady state after repeated charge and discharge. For battery life, the capacity at the 100th cycle was compared with the capacity at the steady state.
[0034]
Examples 2 to 16
A hydrogen storage alloy ingot was manufactured in the same manner as in Example 1 except that the composition of the raw material was as shown in Table 1. About the obtained alloy ingot and the battery using this alloy ingot, the same measurement as Example 1 was performed. The results are shown in Table 2.
[0035]
[Comparative Example 1]
The raw material having the composition shown in Table 1 was processed in exactly the same manner as in Example 1 to produce a strip-shaped alloy ingot. This ingot was put into a heat treatment furnace and heat-treated at 700 ° C. for 4 hours in an argon stream. The same measurement as in Example 1 was performed on this alloy ingot and a battery prepared using this alloy ingot in the same manner as in Example 1. The results are shown in Table 2.
[0036]
[Comparative Example 2]
The raw material having the composition shown in Table 1 was made into an alloy melt in the same manner as in Example 1. This composition is a composition blended beyond the range that defines Gd as the substitution element L. Subsequently, the obtained alloy melt was processed in the same manner as in Example 1 to produce a strip-shaped alloy ingot. This ingot was heat-treated in an argon stream at 700 ° C. for 4 hours. The same measurement as in Example 1 was performed on this alloy ingot and a battery prepared using this alloy ingot in the same manner as in Example 1. The results are shown in Table 2.
[0037]
[Comparative Example 3]
Except using the same alloy melt as in Example 3 and using a cooling rate of 300 to 600 ° C./second, a band-shaped alloy ingot is obtained in the same manner as in Example 1 and heat-treated to obtain a hydrogen storage alloy ingot. It was. The same measurement as in Example 1 was performed on this alloy ingot and a battery prepared using this alloy ingot in the same manner as in Example 1. The results are shown in Table 2.
[0038]
[Comparative Example 4]
The same alloy melt as in Example 3 was treated in the same manner as in Example 1 except that the melt was poured into a water-cooled copper mold at a melt temperature of 1450 ° C. by a mold casting method to form an alloy ingot having a thickness of 20 mm. Then, an alloy ingot and a battery were produced and measured. The results are shown in Table 2.
[0039]
[Table 1]

[0040]
[Table 2]

[Brief description of the drawings]
FIG. 1 is a high-resolution transmission electron micrograph (shown as B in FIG. 2) for measuring the abundance of antiphase boundaries contained in crystal grains of a strip-shaped ingot prepared in Example 1; FIG.
FIG. 2 is a high-resolution transmission electron micrograph for measuring the abundance of crystal grains having antiphase boundaries in the banded ingot prepared in Example 1.
[Explanation of symbols]
A: Antiphase boundary

Claims (2)

The following general formula (1)
(R _1-X L _X ) (Ni _{1- y My} ) _Z (1)
(In the formula, R represents two or more mixed elements of La and at least one of Ce, Pr, and Nd , and L represents Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y, Sc. , Mg, Ca, Ti, Zr, or a mixed element thereof, where M is Co, Al, Mn, Fe, Cu, Mo , Si, V, Cr, Nb, Hf, Ta, W, B, C, or These mixed elements are represented by 0.2 ≦ x ≦ 0.6, 0 ≦ y ≦ 0.5, and 2.0 ≦ z <3.0. The crystal grains containing 20% or more and less than 40% of crystals having an antiphase boundary perpendicular to the C-axis in the direction of the C-axis in the C-axis direction of 50% or more and less than 95% by volume, and the general formula (1) The element represented by L is disposed in the antiphase region in a rare earth metal-ni having 60% or more and less than 95% of the amount added. A nickel-based hydrogen storage alloy.   A negative electrode for a nickel metal hydride secondary battery comprising the rare earth metal-nickel-based hydrogen storage alloy according to claim 1 and a conductive agent as negative electrode materials.

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