JP5331300B2 - Nickel metal hydride secondary battery - Google Patents

Description

The present invention relates to a hydrogen storage alloy for a nickel-metal hydride secondary battery having a high capacity, a long life, and a high capacity from a low temperature to a high temperature, a negative electrode using the same, and a nickel-metal hydride secondary battery. The battery of the present invention is suitable for hybrid vehicles and electric vehicles.

The hydrogen storage alloy is an alloy that can store hydrogen as an energy source safely and easily, and has attracted a great deal of attention for new energy conversion and storage. Applications of hydrogen storage alloys as functional materials include hydrogen storage and transport, heat storage and transport, thermal-mechanical energy conversion, hydrogen separation and purification, hydrogen isotope separation, and hydrogen as the active material Various proposals have been made on batteries, catalysts in synthetic chemistry, and the like.
In particular, a hydrogen storage alloy capable of reversibly storing and releasing hydrogen is actively used as a negative electrode material for secondary batteries. This nickel metal hydride secondary battery is used as a power source for various types of miniaturized and lightweight portable electronic devices. Portable devices have been improved in performance, functionality and size. In order to enable long-time operation of such portable devices, it is necessary to increase the discharge capacity per volume of the secondary battery. is there. In recent years, it has been desired to reduce the weight, that is, increase the discharge capacity per weight, in addition to increasing the discharge capacity per volume.
The LaNi ₅ rare earth hydrogen storage alloy reacts with hydrogen near room temperature and normal pressure and has a relatively high chemical stability. Therefore, research as a hydrogen storage alloy for batteries is currently widely promoted and is commercially available. Used as a negative electrode for secondary batteries.
However, the discharge capacity of a commercially available secondary battery having a negative electrode containing a LaNi ₅ type rare earth hydrogen storage alloy reaches 80% or more of the theoretical capacity, and there is a limit to increasing the capacity beyond this.
By the way, there are many rare earth-Ni intermetallic compounds other than the LaNi ₅ alloy described above. For example, Mat. Res. Bull. 11 p.1241 (1976) (Non-Patent Document 1), an intermetallic compound containing more rare earth elements than a LaNi ₅ alloy occludes a larger amount of hydrogen near room temperature than a LaNi5-type rare earth intermetallic compound. It is disclosed. Also,
A system in which a La site is a mixture of rare earth and Mg is known in the following two documents. One is La _1-x Mg _{x in} J. Less-common metals 73 339 (1980) (non-patent document 2).
A hydrogen storage alloy represented by Ni ₂ has been reported. However, this hydrogen storage alloy has a problem that it is difficult to completely release hydrogen when the secondary battery is discharged because the stability with hydrogen is too high and it is difficult to release hydrogen. On the other hand, the outline of the 120th Spring Meeting of the Japan Institute of Metals p.289 (1997) (Non-patent Document 3) reports a hydrogen storage alloy whose composition is represented by LaMg ₂ Ni ₉ , but this system is also fulfilled. There is a problem that the release of hydrogen during discharge is smaller than that of occlusion.

Japanese Patent Laid-Open No. 63-271348 (Patent Document 1) discloses a general formula Mm _1-x A _x
Hydrogen absorbing electrode comprising a hydrogen storage alloy represented by the Ni _a Co _b M _c is disclosed. on the other hand,
The JP 62-271349 (Patent Document _{2), La 1-x A} x Ni a Co b M c
The hydrogen storage electrode containing the hydrogen storage alloy represented by these is disclosed.
However, the secondary battery provided with these hydrogen storage electrodes has a problem that the discharge capacity is low and the cycle life is short. Furthermore, when used for automobile applications, further improvement in discharge characteristics at low temperatures is required.
In addition, International Publication No. WO 97/03213 (Patent Document 3) and US Patent Publication 584
Japanese Patent No. 0166 (Patent Document 4) discloses a hydrogen storage electrode including a hydrogen storage alloy having a composition represented by the following general formula (i) and having a specific antiphase boundary. The crystal structure of this hydrogen storage alloy consists of a CaCu ₅ type single phase.
(R _1-x L _x ) (Ni _1-y M _y ) _z (i)
In this formula (i), R represents La, Ce, Pr, Nd or a mixed element thereof. L is Gd, Tb, Dy,
Ho, Er, Tm, Yb, Lu, Y, Sc, Mg, Ca or mixed elements thereof are shown. On the other hand, M is Co, Al, Mn, Fe, Cu, Z
r, Ti, Mo, Si, V, Cr, Nb, Hf, Ta, W, B, C or a mixed element thereof is shown. The atomic ratios x, y, and z are 0.05 ≦ x ≦ 0.4, 0 ≦ y ≦ 0.5, and 3.0 ≦ z <4.5.
This hydrogen storage alloy has a supercooling degree of 50 to 500 ° C. and a cooling rate on a roll having irregularities with an average maximum height of 30 to 150 μm on the surface of a molten alloy having the composition represented by the general formula (i). Manufactured by heat treatment after uniformly solidifying to a thickness of 0.1 to 2 mm under cooling conditions of 1000 to 10000 ° C./second. Also, the alloy obtained when this condition is exceeded is CaCu
It has been reported that a LaNi ₅ type single phase cannot be obtained, comprising a crystal grain of a ₅ type crystal structure and a Ce ₂ Ni ₇ type crystal structure.
However, a secondary battery including a negative electrode containing a hydrogen storage alloy whose composition is represented by the above-described formula (i), has a specific antiphase boundary, and has a crystal structure of CaCu ₅ is used particularly for automobiles. There is a problem that the required discharge capacity at low temperatures and the cycle life are lower.
Furthermore, Japanese Patent Application Laid-Open No. 11-29832 (Patent Document 5) discloses a hydrogen storage material having a hexagonal structure whose composition is represented by the general formula shown in (ii) below and whose space group is P63 / mmc. Has been.
_{(R 1-x A x)} 2 (Ni 7-Y-Z-α-β Mn Y Nb z B α C β) n (ii)
However, in said (ii), R is rare earth elements or misch metal (Mm), A is M
at least one selected from g, Ti, Zr, Th, Hf, Si and Ca, C is Ga
And at least one selected from Ge, In, Sn, Sb, Tl, Pb and Bi.
X, Y, Z, α, β and n are 0 <X ≦ 0.3, 0.3 ≦ Y ≦ 1.5, 0 <Z
≦ 0.3, 0 ≦ α ≦ 1, 0 ≦ β ≦ 1, 0.9 ≦ n ≦ 1.1.
In the hydrogen storage alloy having the composition represented by (ii), the atomic ratio of Mn is 0.135 or more and 0.825 or less when the sum of the atomic ratios of R and A is 1.
However, since this hydrogen storage alloy is inferior in the possibility of hydrogen storage and release reaction, there is a problem that the amount of hydrogen storage and release is small. In addition, a battery equipped with a negative electrode containing this hydrogen storage alloy is inferior in reversibility of the hydrogen storage / release reaction, and the operating voltage is lowered, so that the discharge capacity is lowered.

Incidentally, the claims of Japanese Patent Laid-Open No. 10-1731 (Patent Document 6) include A ₅ T
A hydrogen storage alloy including an intermetallic compound phase having a composition represented by ₁₉ is disclosed. Where A is La, Ce, Pr, Sm, Nd, Mm, Y, Gd, Ca, Mg, Ti, Z
and at least one element selected from r and Hf, wherein T is B, Bi, Al, Si
, Cr, V, Mn, Fe, Co, Ni, Cu, Zn, Sn, and Sb.
In this publication, a method described below is disclosed as a method for producing a hydrogen storage alloy including an intermetallic compound phase having a composition of A ₅ T ₁₉ . First, an alloy including an intermetallic compound phase having an AT ₃ composition and an alloy including an intermetallic compound phase having an AT ₄ composition are mixed and mechanically alloyed. In addition to AT ₃ and AT ₄ , it forms an intermetallic phase having a composition of A ₅ T ₁₉ . Subsequently, the obtained alloy and an alloy containing an intermetallic compound phase having the composition of AT ₅ are mixed or mechanically alloyed to obtain a hydrogen storage alloy containing an A ₅ T ₁₉ phase and an AT ₅ phase. Get. In this hydrogen storage alloy, as shown in FIG. 1 of the above-mentioned publication, the entire crystal grain is composed of a region having a composition represented by A ₅ T ₁₉ .
Further, International Publication WO 01/048841 (Patent Document 7) discloses the following (iii):
The hydrogen storage alloy represented by is shown.
R _1-ab Mg _a T _b Ni _1z-xy-α M1 _x M2 _y Mn _α (iii)
However, R is at least 1 selected from rare earth elements (the rare earth elements include Y)
Species element, T is at least one element selected from Ca, Ti, Zr and Hf, M1 is at least one element selected from Fe and Co, M2 is Al, Ga, Zn, Sn, Cu, Si, B, Nb, W, Mo, V, Cr, Ta, Li, P and S
At least one element selected from the group consisting of atomic ratios a, b, x, y, α and Z of 0.1
5 ≦ a ≦ 0.37, 0 ≦ b ≦ 0.3, 0 ≦ x ≦ 1.3, 0 ≦ y ≦ 0.5, 0 ≦ α ≦ 0.1
35, 2.5 ≦ z ≦ 4.2, respectively.
However, in the present invention, it was necessary to develop a hydrogen storage alloy that is more optimal for hybrid vehicles.
Japanese Patent Laid-Open No. 11-323469 (Patent Document 8) discloses a hydrogen storage alloy represented by the following (iV). That is,
(Mg _1-a-b R1 _a M1 _b ) Ni _z (iV)
However, R1 is at least one element selected from rare earth elements including Y, M1 is a larger element of electronegativity than Mg (however, the element of R1, Cr, Mn, Fe, Co, Cu
At least one element selected from (excluding Zn and Ni), a, b, and z are 0.1 ≦ a ≦ 0.8, 0 <b ≦ 0.9, 1-ab> 0, 3 ≦ z ≦ 3.8.
However, this hydrogen storage alloy has not been optimized as a hydrogen storage alloy for hybrid vehicles, and it has been necessary to optimize the hydrogen storage alloy for this application.

JP-A-63-271348 JP 62-271349 A International Publication WO 97/03213 US Patent Publication No. 5840166 Japanese Patent Laid-Open No. 11-29832 JP-A-10-1731 International Publication No. WO01 / 048841 JP-A-11-323469 Mat. Res. Bull. 11 p.1241 (1976) J. Less-common metals 73 339 (1980) Outline of the 120th Spring Meeting of the Japan Institute of Metals p.289 (1997)

The present invention has a problem that hydrogen storage alloy having a composition belonging to a type containing a large amount of La sites compared with LaNi type ₅ is too stable to hydrogen and difficult to release hydrogen. The problem of being susceptible to corrosion and oxidation by the electrolyte is improved, and it provides a hydrogen storage alloy with high hydrogen storage and release. Especially, it is suitable for hybrid vehicles. A life-time hydrogen storage alloy is provided.
In addition, the present invention has a high capacity and a cycle life of −30 ° C.
An object of the present invention is to provide a hydrogen storage alloy for a battery having improved discharge capacity at low temperatures up to the vicinity, a negative electrode using the same, and a nickel-hydrogen secondary battery.

The first hydrogen storage alloy for a battery according to the present invention is represented by R _1-a Mg _a Ni _{b Mc} X _d (1)
R: at least one selected from La, Ce, Pr, Nd, Sm M: at least one selected from Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, Cr, Mo, W X: At least one selected from Al, Ga, Zn, Sn, Si, B, C, and P 0 <a <0.25
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
And a hydrogen storage alloy for a battery comprising two phases of a La ₃ MgNi ₁₄ type crystal phase having at least a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure.
It is. Further, the second hydrogen storage alloy for a battery is represented by the following formula (2): R _1-ax Mg _a A _x Ni _{b Mc} X _d (2)
R: at least one selected from La, Ce, Pr, Nd, Sm A: at least one selected from Ca, Sr, Ba M: Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, At least one selected from Cr, Mo, W X: at least one selected from Al, Ga, Zn, Sn, Si, B, C, P 0 <a <0.25
0 <x ≦ 0.5
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
The hydrogen storage alloy for a battery is characterized by including two phases of a La ₃ MgNi ₁₄ type crystal phase having at least a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure.
Moreover, the negative electrode for nickel metal hydride secondary batteries according to the present invention is represented by R _1-a Mg _a Ni _{b Mc} X _d (1)
R: at least one selected from La, Ce, Pr, Nd, Sm M: at least one selected from Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, Cr, Mo, W X: At least one selected from Al, Ga, Zn, Sn, Si, B, C, and P 0 <a <0.25
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
And a hydrogen storage alloy containing two phases of a La ₃ MgNi ₁₄ type crystal phase having a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure. It is a negative electrode for secondary batteries.

The second negative electrode for a nickel metal hydride secondary battery used in the present invention has the general formula 2 as R _1-ax Mg _a A _x Ni _b M _c X _d (2)
R: at least one selected from La, Ce, Pr, Nd, Sm A: at least one selected from Ca, Sr, Ba M: Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, At least one selected from Cr, Mo, W X: at least one selected from Al, Ga, Zn, Sn, Si, B, C, P 0 <a <0.25
0 <x ≦ 0.5
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
And a hydrogen storage alloy containing two phases of a La ₃ MgNi ₁₄ type crystal phase having at least a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure. Negative electrode.
The nickel metal hydride secondary battery of the present invention is represented by R _{1 -a} Mg _a Ni _{b Mc} X _d (1)
R: at least one selected from La, Ce, Pr, Nd, Sm M: at least one selected from Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, Cr, Mo, W X: At least one selected from Al, Ga, Zn, Sn, Si, B, C, and P 0 <a <0.25
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
A negative electrode, a positive electrode, and an electrolyte solution using a hydrogen storage alloy including two phases of a La ₃ MgNi ₁₄ type crystal phase having a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure A nickel hydride secondary battery comprising:
Further, the second nickel metal hydride secondary battery is represented by the general formula 2,
_{R 1-a-x Mg a} A x Ni b M c X d (2)
R: at least one selected from La, Ce, Pr, Nd, Sm A: at least one selected from Ca, Sr, Ba M: Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, At least one selected from Cr, Mo, W X: at least one selected from Al, Ga, Zn, Sn, Si, B, C, P 0 <a <0.25
0 <x ≦ 0.5
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
A negative electrode, a positive electrode, and an electrolyte solution using a hydrogen storage alloy including two phases of a La ₃ MgNi ₁₄ type crystal phase having a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure It is a nickel metal hydride secondary battery characterized by comprising.

The battery hydrogen-absorbing alloy of the present invention has a high capacity, which is a problem of a nickel-hydrogen secondary battery, and is improved in both cycle life and discharge capacity at a low temperature near -30 ° C. Moreover, the negative electrode for nickel hydride secondary batteries and the nickel hydride secondary battery using the same have excellent characteristics.

The battery hydrogen storage alloy according to the present invention, a negative electrode using the same, and a nickel hydride secondary battery will be described.
The hydrogen storage alloy for a battery of the present invention is represented by R _{1 -a} Mg _a Ni _{b Mc} X _d (1)
R: at least one selected from La, Ce, Pr, Nd, Sm M: at least one selected from Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, Cr, Mo, W X: At least one selected from Al, Ga, Zn, Sn, Si, B, C, and P 0 <a <0.25
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
The hydrogen storage alloy for a battery is characterized by including two phases of a La ₃ MgNi ₁₄ type crystal phase having at least a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure.
Here, R is La, Ce, Pr, Nd, Sm. R is an element that determines the hydrogen storage capacity, and La, Pr, and Nd are mainly used from the viewpoint of life characteristics. In addition, rare earth elements (lanthanoid group) other than these may be contained up to 10 atomic%.
Mg is an element that determines the hydrogen storage capacity like R, but the capacity and life are determined by the ratio (a) with R. The amount is 0 <a <0.25. If Mg is not included, the charge / discharge characteristics are poor, 0.25
Exceeding this causes a problem that the capacity decreases too much. Preferably, 0.05 ≦ x ≦ 0.23
More preferably, 0.1 ≦ x ≦ 0.20.
Ni is an element effective for releasing hydrogen in the hydrogen storage alloy and activating chemical reaction in the electrolytic solution, and its amount b is 3 ≦ b ≦ 4. If it is less than 3, it is difficult to release the stored hydrogen, while if it exceeds 4, the capacity decreases. Preferably, 3.1 ≦ b ≦ 3.9, and more preferably 3.2 ≦ b ≦ 3.8. M is an element effective for improving the charge / discharge cycle characteristics or increasing the capacity, and the amount is 0 ≦ c ≦ 1.0. Preferred M elements are Co, Fe,
Mn and Cu. When c exceeds 1, the capacity decreases. Preferably, 0.05 ≦ c ≦ 0.
8. X is at least one selected from Al, Ga, Zn, Sn, Si, B, C, and P, and is effective in charge / discharge cycle life characteristics. When the amount exceeds 1, the capacity decreases. Preferably 0.1 ≦ d ≦ 0.9. Among X, Al, Zn, Sn, and Si are preferable from the viewpoint of life characteristics.
Here, what is effective for capacity, cycle life, low temperature characteristics, and rate characteristics is the total amount of b and c, and 3.6 <b + c + d ≦ 4.05. If it is 3.6 or less, the rate characteristics are insufficient, while if it exceeds 4.05, the low temperature characteristics deteriorate. Preferably, 3.65 ≦ b + c ≦
4.0.

Further, the second hydrogen storage alloy of the present invention is represented by R ₁ -ax Mg _a A _x Ni _b M _c X _d (2)
R: at least one selected from La, Ce, Pr, Nd, Sm A: at least one selected from Ca, Sr, Ba M: Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, At least one selected from Cr, Mo, W X: at least one selected from Al, Ga, Zn, Sn, Si, B, C, P 0 <a <0.25
0 <x ≦ 0.5
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
The hydrogen storage alloy for a battery is characterized by including two phases of a La ₃ MgNi ₁₄ type crystal phase having a 2H type laminated structure and a La ₂ MgNi ₉ type phase having a 3R laminated structure.
Here, R, M, X and Ni are the same as the first hydrogen storage alloy, and A is at least one selected from Ca, Sr and Ba. A is an element that increases the capacity while maintaining the cycle life. A preferred element is Ca. The quantity x is 0 <x ≦ 0
. 5. If it exceeds 0.5, the cycle life is reduced. Preferably 0.05 ≦ x ≦ 0.
40.
In the hydrogen storage alloy according to the present invention, elements such as N, O, and F may be contained as impurities within a range that does not impair the characteristics of the present alloy. These impurities are preferably in the range of 1 wt% or less.
The hydrogen storage alloy of the present invention does not include at least CaCu5 type crystal structure, La ₃ MgNi ₁₄ type crystal phase having at least 2H type laminated structure and La ₂ M having 3R laminated structure.
Includes two phases of gNi ₉ type. In addition, La ₂ MgNi _9- phase, 3R with 2H-type laminated structure
La ₃ MgNi ₁₄ phase with a laminated structure of type 2H type La ₄ MgNi ₁₉ phase, 3R type L
30% of any of the a ₄ MgNi ₁₉ phases may be contained. Here, 30% means TEM
In the range of the visual field of 200 nm × 200 nm obtained by the evaluation, 10 images are observed, and the area ratio is averaged.

The negative electrode for a nickel metal hydride secondary battery of the present invention is a negative electrode using a hydrogen storage alloy of general formula 1 or general formula 2. The nickel-hydrogen secondary battery of the present invention comprises a positive electrode, an electrolytic solution, and a negative electrode using a hydrogen storage alloy represented by general formula 1 or general formula 2.
The production method for the hydrogen storage alloy of the present invention may be ordinary melting to casting to heat treatment, and may be cooled using a cooling mold or a cooling plate during casting. The heat treatment is preferably performed in an inert atmosphere in the range of 600 to just below the melting point for 1 to 20 hours. In addition, since Mg having a high vapor pressure is included in the heat treatment, it may be under an inert atmosphere such as Ar or He.
In particular, the cooling rate after the heat treatment is preferably 5 ° C./min or less, more preferably 3 ° C.
/ Min, most preferably 1 ° C./min.
The hydrogen storage alloy of the present invention may be subjected to surface treatment in order to exhibit its characteristics more.
The method may be any method such as acid treatment or alkali treatment, and it is preferable to relatively increase the Ni concentration in the vicinity of the powder surface. The acid is preferably hydrochloric acid, nitric acid, or oxalic acid,
In the case of alkali treatment, an aqueous KOH solution of the electrolytic solution may be used, but an aqueous NaOH solution may be used.
In this case, the concentration of the aqueous solution preferably contains 30 to 80% by weight of alkali hydroxide, the treatment temperature is preferably room temperature or higher, and 40 ° C. or higher, more preferably 60 ° C. to shorten the processing time. The boiling point is preferred.
In this case, the process is a process of immersing the hydrogen storage alloy powder in an alkaline aqueous solution,
In some cases, the method comprises a step of washing the surface-treated powder with water.
As for the average particle diameter of the hydrogen storage alloy used for surface treatment, 5-50 micrometers is preferable. If the thickness is less than 5 μm, the hydrogen storage portion decreases due to surface treatment, and as a result, the hydrogen storage amount decreases. On the other hand, 50μ
If it exceeds m, the specific surface area generated by the surface treatment is small, and the high rate discharge and the improvement of the temperature characteristics become insufficient.

Further, the metal salt may be added simultaneously with the surface treatment by addition of ammonia or after delaying the time. The metals that can be used are not particularly limited, but alkaline earth metals such as Mg, Ca, Sr, Ni, C
o There are transition metals such as Cu, rare earth metals including Y, and salts thereof include chlorides, sulfates, nitrates and ammonium salts. The amount of the metal salt to be used is related to the amount of oxides and / or hydroxides finally formed on the surface of the hydrogen storage alloy, and is therefore set in consideration of other conditions and the like.
In the surface treatment of the hydrogen storage alloy using these metal salts, for example, a hydrogen storage alloy powder in which ammonia remains is introduced, and the reaction proceeds in a suspended state by heating and stirring. Further, when the pH is acidic or neutral, an alkali hydroxide or the like is added to make the liquid alkaline.
The temperature in these operations is not particularly limited, and may be performed at an arbitrary liquid temperature from room temperature to 100 ° C., and a desirable liquid temperature is 40 to 80 ° C.
By these operations, metal oxide or metal hydroxide precipitates on the surface of the hydrogen storage alloy powder, so that the life of the hydrogen storage alloy is extended and a hydrogen storage alloy having desired characteristics can be provided.
Surface treatment to the hydrogen storage alloy of the present invention is not limited to electrode activation, self-discharge characteristics, high-rate discharge characteristics and cycle life during known initial charge and discharge, but also temperature characteristics required for batteries used in automobiles. Also realized.

Next, a battery manufacturing method will be described.
1) Negative electrode In this negative electrode, for example, a conductive material is added to the above-mentioned hydrogen storage alloy powder, and the paste is prepared by kneading with a polymer binder and water, filling the conductive material substrate with the paste, and drying. Then, it is produced by molding.
Examples of the conductive substrate on which the hydrogen storage alloy is supported include two-dimensional substrates such as punched metal, expanded metal, and nickel net, and three-dimensional substrates such as felt-like metal porous bodies and sponge-like metal substrates. be able to.
The negative electrode can further contain a binder. Examples of the binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polytetrafluoroethylene, and the like. The negative electrode may contain a conductive material. Examples of the conductive material include carbon black. Also,
Rare earth metal oxides such as Y ₂ O ₃ , Er ₂ O ₃ , Yb ₂ O ₃ , Sm ₂ O _{3 in the} paste,
An oxide such as Mn ₃ O ₄ , LiMn ₂ O ₄ , Nb ₂ 0 ₅ , or SnO ₂ may be added. By including the oxide in the negative electrode, it is possible to improve cycle life at high temperatures. Moreover, the kind of oxide to add can be made into 1 type or 2 types or more. The amount of oxide added is preferably in the range of 0.2 to 5 wt% with respect to the hydrogen storage alloy. A more preferable range is 0.4 to 2 wt%.

2) Positive electrode The positive electrode is only required to be able to be stably charged and discharged in an alkaline electrolyte. For example, a conductive material is added to nickel hydroxide powder as an active material and kneaded with a binder and water. The paste is prepared, filled in a conductive substrate, dried, and then molded.
The nickel hydroxide powder preferably holds a mixture of nickel hydroxide and at least one compound selected from the group consisting of zinc oxide, cobalt oxide, zinc hydroxide and cobalt hydroxide. . A nickel metal hydride secondary battery including a positive electrode including such nickel hydroxide powder and the negative electrode can significantly improve charge / discharge capacity and low-temperature discharge characteristics.
Examples of the conductive material include cobalt oxide, cobalt hydroxide, metallic cobalt, metallic nickel, and carbon.
Examples of the binder include carboxymethylcellulose, methylcellulose, sodium polyacrylate, polytetrafluoroethylene, and polyvinyl alcohol.
Examples of the conductive substrate include a net-like, sponge-like, fiber-like, or felt-like metal porous body made of nickel, stainless steel, or a metal plated with nickel.
3) Separator Examples of the separator include a polypropylene nonwoven fabric, a nylon nonwoven fabric, and a polymer nonwoven fabric such as a nonwoven fabric obtained by mixing polypropylene fibers and nylon fibers.
In particular, a polypropylene nonwoven fabric whose surface is subjected to a hydrophilic treatment is suitable as a separator.
4) Alkaline electrolyte Examples of the alkaline electrolyte include sodium hydroxide aqueous solution, lithium hydroxide aqueous solution, potassium hydroxide aqueous solution, NaOH and LiOH mixed solution, KOH and LiOH mixed solution, and KO.
H, a mixed solution of LiOH and NaOH, or the like can be used.
The nickel metal hydride secondary battery according to the present invention is manufactured, for example, by the method described below. First, an electrode group is prepared by interposing a separator between the positive electrode and the negative electrode, and after the electrode group is housed in a container, an alkaline electrolyte is injected into the container, and then a sealing process is performed. Next, the secondary battery can be manufactured by first charging after being held at a temperature of room temperature or higher, or by holding at a temperature of room temperature or higher after the initial charging. The average particle size of the hydrogen storage alloy powder of the negative electrode is preferably in the range of 15 to 50 μm. When the average particle size is less than 10 μm, the cycle life is shortened, while when it exceeds 50 μm, the low-temperature characteristics tend to deteriorate. Further, there is a possibility that the paste cannot be uniformly applied to the conductive substrate, and battery characteristics vary.

FIG. 1 shows a cylindrical nickel hydride secondary battery which is an example of a nickel hydride secondary battery according to the present invention. As shown in FIG. 1, a negative electrode 11 containing a hydrogen storage alloy and a positive electrode 12 containing nickel oxide.
The separator 13 having electrical insulation is interposed between the sealed container 14 and the sealed container 14. The sealed container 14 is filled with an alkaline electrolyte.
That is, a hydrogen storage alloy electrode (negative electrode) 11 containing a hydrogen storage alloy is wound in a spiral shape with a separator 13 interposed between it and a non-sintered nickel electrode (positive electrode) 12 to form a bottomed cylindrical container. 1
4 is accommodated. The alkaline electrolyte is accommodated in the container 14. A circular sealing plate 16 having a hole 15 in the center is disposed in the upper opening of the container 14. The ring-shaped insulating gasket 17 is disposed between the peripheral edge of the sealing plate 16 and the inner surface of the upper opening of the container 14, and the sealing is performed on the container 14 by caulking to reduce the diameter of the upper opening inward. The plate 16 is airtightly fixed through the gasket 17. The positive electrode lead 18 has one end connected to the positive electrode 12 and the other end connected to the lower surface of the sealing plate 16. A positive electrode terminal 19 having a hat shape is attached on the sealing plate 16 so as to cover the hole 15.
The rubber safety valve 20 is formed in the hole 1 in the space surrounded by the sealing plate 16 and the positive terminal 19.
5 is arranged to block. The insulating tube 21 is attached in the vicinity of the upper end of the container 14 so as to fix the positive terminal 19 and the paper 22 placed on the upper end of the container 14.

The nickel metal hydride secondary battery according to the present invention includes an electrode group having a structure in which positive electrodes and negative electrodes are alternately stacked via separators in addition to the cylindrical nickel metal hydride secondary battery as shown in FIG. The present invention can be similarly applied to a prismatic nickel metal hydride secondary battery having a structure in which a liquid is housed in a bottomed rectangular cylindrical container.
According to such a battery, it is possible to satisfy both a low temperature characteristic around −30 ° C. and a cycle life while maintaining a high discharge capacity.
The hydrogen storage alloy for batteries, negative electrode or Ni-hydrogen secondary battery according to the present invention is suitable for hybrid vehicles and electric vehicles. The hybrid vehicle includes an external combustion engine or an internal combustion engine, an electric drive means such as a motor, and a power source for the electric drive means. The power source includes a nickel metal hydride secondary battery according to the present invention. In the hybrid vehicle, an external combustion engine or an internal combustion engine drives a generator, and an electric drive means drives a wheel by generated electric power and electric power from the secondary battery, an external combustion engine or an internal combustion engine, and an electric drive. It is included that the wheels are driven by using both driving forces of the means.
The electric vehicle according to the present invention includes the nickel metal hydride secondary battery according to the present invention as a drive power source. By using such a Ni hydrogen secondary battery of the present invention, according to the hybrid vehicle and the electric vehicle, driving performance such as fuel efficiency can be improved.

(Example)
(Examples 1-66, Comparative Examples 1-15)
About the alloy of Examples 1-66 shown in Table 1, it produced with the high frequency induction heating furnace in Ar atmosphere. The obtained master alloy was heat-treated in an Ar atmosphere at 1000 ° C. for 5 hours, and then 1 ° C. /
min. Cooled at a speed of. The obtained alloy was coarsely pulverized and then finely pulverized with a hammer mill, and the average particle size was 20 μm. Incidentally, each of the alloys by TEM observation was evaluated the percentage of the main phase (2H-La ₃ MgNi ₁₄ phase and 3R-La ₂ MgNi ₉ phase).
To 100 parts by weight of this alloy powder, 0.5% by weight of nickel powder prepared by a commercially available carbonyl method and 0.5 part by weight of ketjen black powder were added and mixed. To 100 parts by weight of the mixed powder, 1 part by weight of polytetrafluoroethylene, 0.2 part by weight of sodium polyacrylate, 0.2 part by weight of carboxymethyl cellulose, and 50 parts by weight of water are added and stirred to prepare a paste. did. The obtained paste was applied to an iron perforated thin plate whose surface was plated with nickel, and dried to obtain a coated plate. The obtained coated plate was roll-pressed to adjust the thickness, and then cut to a desired size to produce a negative electrode containing a hydrogen storage alloy.
On the other hand, a polyolefin nonwoven fabric in which acrylic acid was graft copolymerized was prepared as a separator.
An electrode group was produced by winding this negative electrode and a paste type nickel positive electrode produced by a known technique having a nominal capacity of 1500 mAh in a spiral shape with the separator interposed therebetween.
The obtained electrode group and 7 mol of KOH, 0.5 mol of NaOH and 0.5 mol of L
By storing 2.5 ml of alkaline electrolyte containing iOH in a close-bottom cylindrical container and sealing it, the structure shown in FIG. 1 described above has a nominal capacity of 1500 mAh and an AA size cylindrical nickel metal hydride. A secondary battery was assembled.

On the other hand, about Comparative Examples 1-15, material was produced with each method shown below, and it used for evaluation.
In Comparative Example 1, after melting in an Ar atmosphere using a high frequency induction heating furnace, a strip-shaped alloy having a thickness of 0.3 to 0.4 mm was produced using a single roll casting apparatus, and the obtained alloy was 850. The sample for evaluation was subjected to heat treatment at 4 ° C. for 4 hours.
In Comparative Example 2, the molten metal melted at high frequency was cast on a cooling plate, and then heat-treated in an Ar atmosphere at 890 ° C. for 12 hours to be used as an evaluation sample.
In Comparative Example 3, 100 g of LaNi ₃ and LaNi ₄ were first mixed and subjected to mechanical alloying treatment in a planetary ball mill containing steel balls for 10 hours at room temperature in an argon atmosphere. LaNi ₅ alloy 100g is mechanically alloyed under the same conditions, LaNi ₃ , LaNi ₄ , L
Samples made of a ₅ Ni ₁₉ and LaNi ₅ phases were prepared.
In Comparative Example 4, an alloy having the composition shown in the table was prepared in an arc melting furnace in an Ar atmosphere, and then heat-treated at 900 ° C. for 12 hours to obtain a measurement sample.
In Comparative Example 5, after melting in an Ar atmosphere using a high frequency induction heating furnace, heat treatment was performed at 900 ° C. for 10 hours.
Comparative Examples 6 to 14 were melted in an Ar atmosphere using a high frequency induction heating furnace, and then 10 ° C. at 900 ° C.
Time heat treatment was performed.
Comparative Example 15 is La0.7Mg0.3Ni2.5Co0.5 using a high frequency induction heating furnace.
After dissolution in an Ar atmosphere, heat treatment was performed at 900 ° C. for 10 hours. As a result of analyzing the crystal structure of the obtained sample, 3R-PuNi ₃ type La ₂ MgNi ₉ phase is 50%, 2H-Ce ₂ Ni ₇ type La ₃ MgNi ₁₄ phase is 25%
The 2H—Pr ₅ Co ₁₉ type La ₄ MgNi ₁₉ phase was 15%, and the C15b type LaMgNi ₄ phase was 9%.

All the samples of the comparative examples described above were pulverized by a jet mill to an average particle size of 20 μm, and then a secondary battery was produced in the same manner as in the example.
The obtained secondary batteries of Examples 1 to 66 and Comparative Examples 1 to 15 were left at room temperature for 36 hours. Subsequently, after charging for 15 hours at 150 mA, the battery voltage was 0.8 at a current of 150 mA.
The charge / discharge cycle for discharging to V was performed twice. Thereafter, the charge / discharge cycle is repeated under an environment of 45 ° C., the number of cycles until the discharge capacity reaches 80% or less of the discharge capacity of the first cycle is measured, and the number of cycles and the discharge capacity of the first cycle are represented. Shown in The charging process of the charging / discharging cycle was performed by using a -ΔV method in which the charging current was set to 1500 mA and the charging was terminated when the maximum voltage during charging was reduced by 10 mV. On the other hand, the discharging process was performed at a current of 3000 mA until the battery voltage reached 1.0V.
Evaluation is capacity, charge / discharge cycle life, low temperature characteristics (-30 ° C discharge capacity compared to room temperature)
High rate discharge characteristics.
As is apparent from Tables 1 to 3, the nickel-metal hydride secondary battery using the hydrogen storage alloy of the present invention has excellent characteristics. From a commercially available battery that replaces general AA 3 and 4 such as a normal digital camera battery, It turns out that it is a battery suitable for a hybrid vehicle.

(Examples 67 to 70)
The mother alloy having the composition of Example 1 shown in Table 1 was produced under the same conditions. The obtained master alloy was heat-treated at 1000 ° C. for 5 hours in an Ar atmosphere, and then cooled to 400 ° C. at various speeds. Each cooling rate is 5 ° C./min. In Example 67. Example 68 is 2.5 ° C./m
in. , Example 69 was 0.5 ° C./min. Example 70 is 0.1 ° C./min. It is. Each of the obtained alloys was coarsely pulverized and then finely pulverized with a hammer mill to obtain an average particle size of 20 μm.
A negative electrode was produced in the same manner as in Example 1. After that, a battery was prepared together with the positive electrode and the separator and subjected to evaluation.
The obtained secondary batteries of Examples 67 to 72 were left at room temperature for 36 hours. Continue,
After charging at 150 mA for 15 hours, a charge / discharge cycle was performed twice, in which discharging was performed at a current of 150 mA until the battery voltage reached 0.8 V. After this, the charge / discharge cycle is repeated under an environment of 45 ° C.,
The number of cycles until the discharge capacity reaches 80% or less of the discharge capacity of the first cycle is measured, and the number of cycles and the discharge capacity of the first cycle are shown in the table. The charging process of the charging / discharging cycle was performed by using a -ΔV method in which the charging current was set to 1500 mA and the charging was terminated when the voltage decreased by 10 mV from the maximum voltage during charging. On the other hand, the discharge process is 3000 mA and the battery voltage is 1
. It went until it became 0V.
Evaluation is capacity, charge / discharge cycle life, low temperature characteristics (-30 ° C discharge capacity compared to room temperature)
High rate discharge characteristics.
As is apparent from Table 4, the nickel-metal hydride secondary battery using the hydrogen storage alloy of the present invention has excellent characteristics. From a commercially available battery replacing a general AA battery such as a normal digital camera battery, a hybrid vehicle It turns out that it is a battery suitable for use.

(Examples 71-89)
In the same manner as in Example 1, hydrogen storage alloys of Examples 71 to 89 were produced. The average particle size is 25
After pulverizing to μm, in Examples 71 to 74, a 50 wt% KOH aqueous solution was set to 60 ° C., and the hydrogen storage alloy powder was immersed in the surface treatment. In Examples 75 to 78, a surface treatment was performed by immersing the hydrogen storage alloy powder in a 60 wt% NaOH aqueous solution at 70 ° C. In Examples 79 to 80, the pH was set to 2 using hydrochloric acid, and surface treatment was performed by immersing the hydrogen storage alloy powder in a 40 ° C. aqueous solution. Examples 81-82 use nitric acid to adjust the pH to 2
And the surface treatment was performed by immersing the hydrogen storage alloy powder in an aqueous solution at 60 ° C.
Examples 83 to 84 were subjected to surface treatment in an aqueous solution set to pH 4 using oxalic acid and adjusted to 50 ° C., and Examples 85 to 89 were subjected to surface treatment with ammonia.
A negative electrode was produced in the same manner as in Example 1 using the obtained hydrogen storage alloy powder. After that, a battery was prepared together with the positive electrode and the separator and subjected to evaluation.
The obtained secondary batteries of Examples 71 to 89 and Comparative Examples 1 to 10 were left at room temperature for 36 hours. Subsequently, after charging for 15 hours at 150 mA, the battery voltage was reduced to 0.1 at a current of 150 mA.
The charge / discharge cycle for discharging to 8V was performed twice. Thereafter, the charge / discharge cycle is repeated under an environment of 45 ° C., the number of cycles until the discharge capacity reaches 80% or less of the discharge capacity of the first cycle is measured, and the number of cycles and the discharge capacity of the first cycle are represented. Shown in In addition,
Charging process of charging / discharging cycle Charging current is set to 1500 mA and 10 mV from the maximum voltage during charging.
The charging was terminated by using the -ΔV method which ends charging. On the other hand, the discharge process is 3000 mA.
The battery voltage was 1.0 V at a current of
The numerical evaluation is capacity, life, low temperature characteristics, and high rate discharge characteristics.
As is apparent from Table 4, the nickel metal hydride secondary battery using the hydrogen storage alloy of the present invention has excellent characteristics, and is found to be a battery suitable for a hybrid vehicle and an electric vehicle.

(Examples 90 to 94)
In the same manner as in Example 1, hydrogen storage alloys of Examples 90 to 94 were produced. Average particle size 25μ
After crushing as m, 1% by weight of rare earth oxide was mixed when producing the negative electrode.
A negative electrode was produced in the same manner as in Example 1 using the obtained hydrogen storage alloy powder. After that, a battery was prepared together with the positive electrode and the separator and subjected to evaluation.
The obtained secondary batteries of Examples 90 to 94 were left at room temperature for 36 hours. Continue,
After charging at 150 mA for 15 hours, a charge / discharge cycle was performed twice, in which discharging was performed at a current of 150 mA until the battery voltage reached 0.8 V. After this, the charge / discharge cycle is repeated under an environment of 45 ° C.,
The number of cycles until the discharge capacity reaches 80% or less of the discharge capacity of the first cycle is measured, and the number of cycles and the discharge capacity of the first cycle are shown in the table. The charging process of the charging / discharging cycle was performed by using a -ΔV method in which the charging current was set to 1500 mA and the charging was terminated when the voltage decreased by 10 mV from the maximum voltage during charging. On the other hand, the discharge process is 3000 mA and the battery voltage is 1
. It went until it became 0V.
As is clear from Table 2, the nickel metal hydride secondary battery using the hydrogen storage alloy of the present invention has excellent characteristics, not only for ordinary single 2, 3, 4, etc. batteries, but also for hybrid vehicles, and It turns out that it is a battery suitable for electric vehicles.

1 is a perspective view showing a nickel hydrogen secondary battery according to an embodiment of the present invention, partially broken away.

Explanation of symbols

11 Hydrogen storage alloy electrode (negative electrode)
12 Non-sintered nickel electrode (positive electrode)
13 Separator 14 Container 15 Hole 16 Sealing plate 17 Insulating gasket 18 Positive electrode lead 19 Positive electrode terminal 20 Safety valve 21 Insulating tube 22 Paper

Claims (2)

General formula 1: R _1-a Mg _a Ni _b M _c X _d
R: At least one selected from La, Ce, Pr, Nd, and Sm
M: selected from Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, Cr, Mo, W
At least one
X: at least one selected from Al, Ga, Zn, Sn, Si, B, C, and P
0 <a <0.25
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
And at least CaCu ₅ Type crystal phase is not included, and La having a 2H type laminated structure ₃ Mg
Ni ₁₄ La with a laminated crystal phase and 3R laminated structure ₂ MgNi ₉ The total of the two phases of the mold phase is an area ratio of 9
A negative electrode, a positive electrode, and an electrolyte using a hydrogen storage alloy having an average particle size of 10 to 50 μm including 0% or more
Therefore, the discharge capacity at −30 ° C. compared to room temperature is 0.36 or more.
Nickel metal hydride secondary battery. General formula 2: R _1-ax Mg _a A _x Ni _b M _c X _d
R: At least one selected from La, Ce, Pr, Nd, and Sm
A: At least one selected from Ca, Sr, and Ba
M: selected from Fe, Co, Mn, Cu, Ti, Zr, V, Nb, Ta, Cr, Mo, W
At least one
X: at least one selected from Al, Ga, Zn, Sn, Si, B, C, and P
0 <a <0.25
0 <x ≦ 0.5
3.0 ≦ b ≦ 4.0
0 ≦ c ≦ 1.0
0.1 ≦ d ≦ 1.0
3.6 <b + c + d ≦ 4.05
And at least CaCu ₅ Type crystal phase is not included, and La having a 2H type laminated structure ₃ Mg
Ni ₁₄ La with a laminated crystal phase and 3R laminated structure ₂ MgNi ₉ The total of the two phases of the mold phase is an area ratio of 9
A negative electrode, a positive electrode, and an electrolyte using a hydrogen storage alloy having an average particle size of 10 to 50 μm including 0% or more
Therefore, the discharge capacity at −30 ° C. compared to room temperature is 0.36 or more.
Nickel metal hydride secondary battery.

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